/* * CDDL HEADER START * * The contents of this file are subject to the terms of the * Common Development and Distribution License (the "License"). * You may not use this file except in compliance with the License. * * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE * or http://www.opensolaris.org/os/licensing. * See the License for the specific language governing permissions * and limitations under the License. * * When distributing Covered Code, include this CDDL HEADER in each * file and include the License file at usr/src/OPENSOLARIS.LICENSE. * If applicable, add the following below this CDDL HEADER, with the * fields enclosed by brackets "[]" replaced with your own identifying * information: Portions Copyright [yyyy] [name of copyright owner] * * CDDL HEADER END */ /* * Copyright 2009 Sun Microsystems, Inc. All rights reserved. * Use is subject to license terms. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* needed for S_IFBLK and S_IFCHR */ #include #include #include #include #include #include #include #include /* * This module implements the file system snapshot code, which provides a * point-in-time image of a file system for the purposes of online backup. * There are essentially two parts to this project: the driver half and the * file system half. The driver half is a pseudo device driver called * "fssnap" that represents the snapshot. Each snapshot is assigned a * number that corresponds to the minor number of the device, and a control * device with a high minor number is used to initiate snapshot creation and * deletion. For all practical purposes the driver half acts like a * read-only disk device whose contents are exactly the same as the master * file system at the time the snapshot was created. * * The file system half provides interfaces necessary for performing the * file system dependent operations required to create and delete snapshots * and a special driver strategy routine that must always be used by the file * system for snapshots to work correctly. * * When a snapshot is to be created, the user utility will send an ioctl to * the control device of the driver half specifying the file system to be * snapshotted, the file descriptor of a backing-store file which is used to * hold old data before it is overwritten, and other snapshot parameters. * This ioctl is passed on to the file system specified in the original * ioctl request. The file system is expected to be able to flush * everything out to make the file system consistent and lock it to ensure * no changes occur while the snapshot is being created. It then calls * fssnap_create() to create state for a new snapshot, from which an opaque * handle is returned with the snapshot locked. Next, the file system must * populate the "candidate bitmap", which tells the snapshot code which * "chunks" should be considered for copy-on-write (a chunk is the unit of * granularity used for copy-on-write, which is independent of the device * and file system block sizes). This is typically done by scanning the * file system allocation bitmaps to determine which chunks contain * allocated blocks in the file system at the time the snapshot was created. * If a chunk has no allocated blocks, it does not need to be copied before * being written to. Once the candidate bitmap is populated with * fssnap_set_candidate(), the file system calls fssnap_create_done() to * complete the snapshot creation and unlock the snapshot. The file system * may now be unlocked and modifications to it resumed. * * Once a snapshot is created, the file system must perform all writes * through a special strategy routine, fssnap_strategy(). This strategy * routine determines whether the chunks contained by the write must be * copied before being overwritten by consulting the candidate bitmap * described above, and the "hastrans bitmap" which tells it whether the chunk * has been copied already or not. If the chunk is a candidate but has not * been copied, it reads the old data in and adds it to a queue. The * old data can then be overwritten with the new data. An asynchronous * task queue is dispatched for each old chunk read in which writes the old * data to the backing file specified at snapshot creation time. The * backing file is a sparse file the same size as the file system that * contains the old data at the offset that data originally had in the * file system. If the queue containing in-memory chunks gets too large, * writes to the file system may be throttled by a semaphore until the * task queues have a chance to push some of the chunks to the backing file. * * With the candidate bitmap, the hastrans bitmap, the data on the master * file system, and the old data in memory and in the backing file, the * snapshot pseudo-driver can piece together the original file system * information to satisfy read requests. If the requested chunk is not a * candidate, it returns a zeroed buffer. If the chunk is a candidate but * has not been copied it reads it from the master file system. If it is a * candidate and has been copied, it either copies the data from the * in-memory queue or it reads it in from the backing file. The result is * a replication of the original file system that can be backed up, mounted, * or manipulated by other file system utilities that work on a read-only * device. * * This module is divided into three roughly logical sections: * * - The snapshot driver, which is a character/block driver * representing the snapshot itself. These routines are * prefixed with "snap_". * * - The library routines that are defined in fssnap_if.h that * are used by file systems that use this snapshot implementation. * These functions are prefixed with "fssnap_" and are called through * a function vector from the file system. * * - The helper routines used by the snapshot driver and the fssnap * library routines for managing the translation table and other * useful functions. These routines are all static and are * prefixed with either "fssnap_" or "transtbl_" if they * are specifically used for translation table activities. */ static dev_info_t *fssnap_dip = NULL; static struct snapshot_id *snapshot = NULL; static struct snapshot_id snap_ctl; static int num_snapshots = 0; static kmutex_t snapshot_mutex; static char snapname[] = SNAP_NAME; /* "tunable" parameters */ static int fssnap_taskq_nthreads = FSSNAP_TASKQ_THREADS; static uint_t fssnap_max_mem_chunks = FSSNAP_MAX_MEM_CHUNKS; static int fssnap_taskq_maxtasks = FSSNAP_TASKQ_MAXTASKS; /* static function prototypes */ /* snapshot driver */ static int snap_getinfo(dev_info_t *, ddi_info_cmd_t, void *, void **); static int snap_attach(dev_info_t *dip, ddi_attach_cmd_t cmd); static int snap_detach(dev_info_t *dip, ddi_detach_cmd_t cmd); static int snap_open(dev_t *devp, int flag, int otyp, cred_t *cred); static int snap_close(dev_t dev, int flag, int otyp, cred_t *cred); static int snap_strategy(struct buf *bp); static int snap_read(dev_t dev, struct uio *uiop, cred_t *credp); static int snap_print(dev_t dev, char *str); static int snap_ioctl(dev_t dev, int cmd, intptr_t arg, int mode, cred_t *credp, int *rvalp); static int snap_prop_op(dev_t dev, dev_info_t *dip, ddi_prop_op_t prop_op, int flags, char *name, caddr_t valuep, int *lengthp); static int snap_getchunk(struct snapshot_id *sidp, chunknumber_t chunk, int offset, int len, char *buffer); /* fssnap interface implementations (see fssnap_if.h) */ static void fssnap_strategy_impl(void *, struct buf *); static void *fssnap_create_impl(chunknumber_t, uint_t, u_offset_t, struct vnode *, int, struct vnode **, char *, u_offset_t); static void fssnap_set_candidate_impl(void *, chunknumber_t); static int fssnap_is_candidate_impl(void *, u_offset_t); static int fssnap_create_done_impl(void *); static int fssnap_delete_impl(void *); /* fssnap interface support routines */ static int fssnap_translate(struct snapshot_id **, struct buf *); static void fssnap_write_taskq(void *); static void fssnap_create_kstats(snapshot_id_t *, int, const char *, const char *); static int fssnap_update_kstat_num(kstat_t *, int); static void fssnap_delete_kstats(struct cow_info *); /* translation table prototypes */ static cow_map_node_t *transtbl_add(cow_map_t *, chunknumber_t, caddr_t); static cow_map_node_t *transtbl_get(cow_map_t *, chunknumber_t); static void transtbl_delete(cow_map_t *, cow_map_node_t *); static void transtbl_free(cow_map_t *); static kstat_t *fssnap_highwater_kstat; /* ************************************************************************ */ /* Device and Module Structures */ static struct cb_ops snap_cb_ops = { snap_open, snap_close, snap_strategy, snap_print, nodev, /* no snap_dump */ snap_read, nodev, /* no snap_write */ snap_ioctl, nodev, /* no snap_devmap */ nodev, /* no snap_mmap */ nodev, /* no snap_segmap */ nochpoll, snap_prop_op, NULL, /* streamtab */ D_64BIT | D_NEW | D_MP, /* driver compatibility */ CB_REV, nodev, /* async I/O read entry point */ nodev /* async I/O write entry point */ }; static struct dev_ops snap_ops = { DEVO_REV, 0, /* ref count */ snap_getinfo, nulldev, /* snap_identify obsolete */ nulldev, /* no snap_probe */ snap_attach, snap_detach, nodev, /* no snap_reset */ &snap_cb_ops, (struct bus_ops *)NULL, nulldev, /* no snap_power() */ ddi_quiesce_not_needed, /* quiesce */ }; extern struct mod_ops mod_driverops; static struct modldrv md = { &mod_driverops, /* Type of module. This is a driver */ "snapshot driver", /* Name of the module */ &snap_ops, }; static struct modlinkage ml = { MODREV_1, &md, NULL }; static void *statep; int _init(void) { int error; kstat_t *ksp; kstat_named_t *ksdata; error = ddi_soft_state_init(&statep, sizeof (struct snapshot_id *), 1); if (error) { cmn_err(CE_WARN, "_init: failed to init ddi_soft_state."); return (error); } error = mod_install(&ml); if (error) { cmn_err(CE_WARN, "_init: failed to mod_install."); ddi_soft_state_fini(&statep); return (error); } /* * Fill in the snapshot operations vector for file systems * (defined in fssnap_if.c) */ snapops.fssnap_create = fssnap_create_impl; snapops.fssnap_set_candidate = fssnap_set_candidate_impl; snapops.fssnap_is_candidate = fssnap_is_candidate_impl; snapops.fssnap_create_done = fssnap_create_done_impl; snapops.fssnap_delete = fssnap_delete_impl; snapops.fssnap_strategy = fssnap_strategy_impl; mutex_init(&snapshot_mutex, NULL, MUTEX_DEFAULT, NULL); /* * Initialize the fssnap highwater kstat */ ksp = kstat_create(snapname, 0, FSSNAP_KSTAT_HIGHWATER, "misc", KSTAT_TYPE_NAMED, 1, 0); if (ksp != NULL) { ksdata = (kstat_named_t *)ksp->ks_data; kstat_named_init(ksdata, FSSNAP_KSTAT_HIGHWATER, KSTAT_DATA_UINT32); ksdata->value.ui32 = 0; kstat_install(ksp); } else { cmn_err(CE_WARN, "_init: failed to create highwater kstat."); } fssnap_highwater_kstat = ksp; return (0); } int _info(struct modinfo *modinfop) { return (mod_info(&ml, modinfop)); } int _fini(void) { int error; error = mod_remove(&ml); if (error) return (error); ddi_soft_state_fini(&statep); /* * delete the fssnap highwater kstat */ kstat_delete(fssnap_highwater_kstat); mutex_destroy(&snapshot_mutex); /* Clear out the file system operations vector */ snapops.fssnap_create = NULL; snapops.fssnap_set_candidate = NULL; snapops.fssnap_create_done = NULL; snapops.fssnap_delete = NULL; snapops.fssnap_strategy = NULL; return (0); } /* ************************************************************************ */ /* * Snapshot Driver Routines * * This section implements the snapshot character and block drivers. The * device will appear to be a consistent read-only file system to * applications that wish to back it up or mount it. The snapshot driver * communicates with the file system through the translation table, which * tells the snapshot driver where to find the data necessary to piece * together the frozen file system. The data may either be on the master * device (no translation exists), in memory (a translation exists but has * not been flushed to the backing store), or in the backing store file. * The read request may require the snapshot driver to retrieve data from * several different places and piece it together to look like a single * contiguous read. * * The device minor number corresponds to the snapshot number in the list of * snapshot identifiers. The soft state for each minor number is simply a * pointer to the snapshot id, which holds all of the snapshot state. One * minor number is designated as the control device. All snapshot create * and delete requests go through the control device to ensure this module * is properly loaded and attached before the file system starts calling * routines defined here. */ /* * snap_getinfo() - snapshot driver getinfo(9E) routine * */ /*ARGSUSED*/ static int snap_getinfo(dev_info_t *dip, ddi_info_cmd_t infocmd, void *arg, void **result) { switch (infocmd) { case DDI_INFO_DEVT2DEVINFO: *result = fssnap_dip; return (DDI_SUCCESS); case DDI_INFO_DEVT2INSTANCE: *result = 0; /* we only have one instance */ return (DDI_SUCCESS); } return (DDI_FAILURE); } /* * snap_attach() - snapshot driver attach(9E) routine * * sets up snapshot control device and control state. The control state * is a pointer to an "anonymous" snapshot_id for tracking opens and closes */ static int snap_attach(dev_info_t *dip, ddi_attach_cmd_t cmd) { int error; switch (cmd) { case DDI_ATTACH: /* create the control device */ error = ddi_create_priv_minor_node(dip, SNAP_CTL_NODE, S_IFCHR, SNAP_CTL_MINOR, DDI_PSEUDO, PRIVONLY_DEV, PRIV_SYS_CONFIG, PRIV_SYS_CONFIG, 0666); if (error == DDI_FAILURE) { return (DDI_FAILURE); } rw_init(&snap_ctl.sid_rwlock, NULL, RW_DEFAULT, NULL); rw_enter(&snap_ctl.sid_rwlock, RW_WRITER); fssnap_dip = dip; snap_ctl.sid_snapnumber = SNAP_CTL_MINOR; /* the control sid is not linked into the snapshot list */ snap_ctl.sid_next = NULL; snap_ctl.sid_cowinfo = NULL; snap_ctl.sid_flags = 0; rw_exit(&snap_ctl.sid_rwlock); ddi_report_dev(dip); return (DDI_SUCCESS); case DDI_PM_RESUME: return (DDI_SUCCESS); case DDI_RESUME: return (DDI_SUCCESS); default: return (DDI_FAILURE); } } /* * snap_detach() - snapshot driver detach(9E) routine * * destroys snapshot control device and control state. If any snapshots * are active (ie. num_snapshots != 0), the device will refuse to detach. */ static int snap_detach(dev_info_t *dip, ddi_detach_cmd_t cmd) { struct snapshot_id *sidp, *sidnextp; switch (cmd) { case DDI_DETACH: /* do not detach if the device is active */ mutex_enter(&snapshot_mutex); if ((num_snapshots != 0) || ((snap_ctl.sid_flags & SID_CHAR_BUSY) != 0)) { mutex_exit(&snapshot_mutex); return (DDI_FAILURE); } /* free up the snapshot list */ for (sidp = snapshot; sidp != NULL; sidp = sidnextp) { ASSERT(SID_AVAILABLE(sidp) && !RW_LOCK_HELD(&sidp->sid_rwlock)); sidnextp = sidp->sid_next; rw_destroy(&sidp->sid_rwlock); kmem_free(sidp, sizeof (struct snapshot_id)); } snapshot = NULL; /* delete the control device */ ddi_remove_minor_node(dip, SNAP_CTL_NODE); fssnap_dip = NULL; ASSERT((snap_ctl.sid_flags & SID_CHAR_BUSY) == 0); rw_destroy(&snap_ctl.sid_rwlock); mutex_exit(&snapshot_mutex); return (DDI_SUCCESS); default: return (DDI_FAILURE); } } /* * snap_open() - snapshot driver open(9E) routine * * marks the snapshot id as busy so it will not be recycled when deleted * until the snapshot is closed. */ /* ARGSUSED */ static int snap_open(dev_t *devp, int flag, int otyp, cred_t *cred) { minor_t minor; struct snapshot_id **sidpp, *sidp; /* snapshots are read-only */ if (flag & FWRITE) return (EROFS); minor = getminor(*devp); if (minor == SNAP_CTL_MINOR) { /* control device must be opened exclusively */ if (((flag & FEXCL) != FEXCL) || (otyp != OTYP_CHR)) return (EINVAL); rw_enter(&snap_ctl.sid_rwlock, RW_WRITER); if ((snap_ctl.sid_flags & SID_CHAR_BUSY) != 0) { rw_exit(&snap_ctl.sid_rwlock); return (EBUSY); } snap_ctl.sid_flags |= SID_CHAR_BUSY; rw_exit(&snap_ctl.sid_rwlock); return (0); } sidpp = ddi_get_soft_state(statep, minor); if (sidpp == NULL || *sidpp == NULL) return (ENXIO); sidp = *sidpp; rw_enter(&sidp->sid_rwlock, RW_WRITER); if ((flag & FEXCL) && SID_BUSY(sidp)) { rw_exit(&sidp->sid_rwlock); return (EAGAIN); } ASSERT(sidpp != NULL && sidp != NULL); /* check to see if this snapshot has been killed on us */ if (SID_INACTIVE(sidp)) { cmn_err(CE_WARN, "snap_open: snapshot %d does not exist.", minor); rw_exit(&sidp->sid_rwlock); return (ENXIO); } switch (otyp) { case OTYP_CHR: sidp->sid_flags |= SID_CHAR_BUSY; break; case OTYP_BLK: sidp->sid_flags |= SID_BLOCK_BUSY; break; default: rw_exit(&sidp->sid_rwlock); return (EINVAL); } rw_exit(&sidp->sid_rwlock); /* * at this point if a valid snapshot was found then it has * been marked busy and we can use it. */ return (0); } /* * snap_close() - snapshot driver close(9E) routine * * unsets the busy bits in the snapshot id. If the snapshot has been * deleted while the snapshot device was open, the close call will clean * up the remaining state information. */ /* ARGSUSED */ static int snap_close(dev_t dev, int flag, int otyp, cred_t *cred) { struct snapshot_id **sidpp, *sidp; minor_t minor; char name[20]; minor = getminor(dev); /* if this is the control device, close it and return */ if (minor == SNAP_CTL_MINOR) { rw_enter(&snap_ctl.sid_rwlock, RW_WRITER); snap_ctl.sid_flags &= ~(SID_CHAR_BUSY); rw_exit(&snap_ctl.sid_rwlock); return (0); } sidpp = ddi_get_soft_state(statep, minor); if (sidpp == NULL || *sidpp == NULL) { cmn_err(CE_WARN, "snap_close: could not find state for " "snapshot %d.", minor); return (ENXIO); } sidp = *sidpp; mutex_enter(&snapshot_mutex); rw_enter(&sidp->sid_rwlock, RW_WRITER); /* Mark the snapshot as not being busy anymore */ switch (otyp) { case OTYP_CHR: sidp->sid_flags &= ~(SID_CHAR_BUSY); break; case OTYP_BLK: sidp->sid_flags &= ~(SID_BLOCK_BUSY); break; default: mutex_exit(&snapshot_mutex); rw_exit(&sidp->sid_rwlock); return (EINVAL); } if (SID_AVAILABLE(sidp)) { /* * if this is the last close on a snapshot that has been * deleted, then free up the soft state. The snapdelete * ioctl does not free this when the device is in use so * we do it here after the last reference goes away. */ /* remove the device nodes */ ASSERT(fssnap_dip != NULL); (void) snprintf(name, sizeof (name), "%d", sidp->sid_snapnumber); ddi_remove_minor_node(fssnap_dip, name); (void) snprintf(name, sizeof (name), "%d,raw", sidp->sid_snapnumber); ddi_remove_minor_node(fssnap_dip, name); /* delete the state structure */ ddi_soft_state_free(statep, sidp->sid_snapnumber); num_snapshots--; } mutex_exit(&snapshot_mutex); rw_exit(&sidp->sid_rwlock); return (0); } /* * snap_read() - snapshot driver read(9E) routine * * reads data from the snapshot by calling snap_strategy() through physio() */ /* ARGSUSED */ static int snap_read(dev_t dev, struct uio *uiop, cred_t *credp) { minor_t minor; struct snapshot_id **sidpp; minor = getminor(dev); sidpp = ddi_get_soft_state(statep, minor); if (sidpp == NULL || *sidpp == NULL) { cmn_err(CE_WARN, "snap_read: could not find state for snapshot %d.", minor); return (ENXIO); } return (physio(snap_strategy, NULL, dev, B_READ, minphys, uiop)); } /* * snap_strategy() - snapshot driver strategy(9E) routine * * cycles through each chunk in the requested buffer and calls * snap_getchunk() on each chunk to retrieve it from the appropriate * place. Once all of the parts are put together the requested buffer * is returned. The snapshot driver is read-only, so a write is invalid. */ static int snap_strategy(struct buf *bp) { struct snapshot_id **sidpp, *sidp; minor_t minor; chunknumber_t chunk; int off, len; u_longlong_t reqptr; int error = 0; size_t chunksz; caddr_t buf; /* snapshot device is read-only */ if (bp->b_flags & B_WRITE) { bioerror(bp, EROFS); bp->b_resid = bp->b_bcount; biodone(bp); return (0); } minor = getminor(bp->b_edev); sidpp = ddi_get_soft_state(statep, minor); if (sidpp == NULL || *sidpp == NULL) { cmn_err(CE_WARN, "snap_strategy: could not find state for snapshot %d.", minor); bioerror(bp, ENXIO); bp->b_resid = bp->b_bcount; biodone(bp); return (0); } sidp = *sidpp; ASSERT(sidp); rw_enter(&sidp->sid_rwlock, RW_READER); if (SID_INACTIVE(sidp)) { bioerror(bp, ENXIO); bp->b_resid = bp->b_bcount; biodone(bp); rw_exit(&sidp->sid_rwlock); return (0); } if (bp->b_flags & (B_PAGEIO|B_PHYS)) bp_mapin(bp); bp->b_resid = bp->b_bcount; ASSERT(bp->b_un.b_addr); buf = bp->b_un.b_addr; chunksz = sidp->sid_cowinfo->cow_map.cmap_chunksz; /* reqptr is the current DEV_BSIZE offset into the device */ /* chunk is the chunk containing reqptr */ /* len is the length of the request (in the current chunk) in bytes */ /* off is the byte offset into the current chunk */ reqptr = bp->b_lblkno; while (bp->b_resid > 0) { chunk = dbtocowchunk(&sidp->sid_cowinfo->cow_map, reqptr); off = (reqptr % (chunksz >> DEV_BSHIFT)) << DEV_BSHIFT; len = min(chunksz - off, bp->b_resid); ASSERT((off + len) <= chunksz); if ((error = snap_getchunk(sidp, chunk, off, len, buf)) != 0) { /* * EINVAL means the user tried to go out of range. * Anything else means it's likely that we're * confused. */ if (error != EINVAL) { cmn_err(CE_WARN, "snap_strategy: error " "calling snap_getchunk, chunk = %llu, " "offset = %d, len = %d, resid = %lu, " "error = %d.", chunk, off, len, bp->b_resid, error); } bioerror(bp, error); biodone(bp); rw_exit(&sidp->sid_rwlock); return (0); } bp->b_resid -= len; reqptr += (len >> DEV_BSHIFT); buf += len; } ASSERT(bp->b_resid == 0); biodone(bp); rw_exit(&sidp->sid_rwlock); return (0); } /* * snap_getchunk() - helper function for snap_strategy() * * gets the requested data from the appropriate place and fills in the * buffer. chunk is the chunk number of the request, offset is the * offset into that chunk and must be less than the chunk size. len is * the length of the request starting at offset, and must not exceed a * chunk boundary. buffer is the address to copy the data to. len * bytes are copied into the buffer starting at the location specified. * * A chunk is located according to the following algorithm: * - If the chunk does not have a translation or is not a candidate * for translation, it is read straight from the master device. * - If the chunk does have a translation, then it is either on * disk or in memory: * o If it is in memory the requested data is simply copied out * of the in-memory buffer. * o If it is in the backing store, it is read from there. * * This function does the real work of the snapshot driver. */ static int snap_getchunk(struct snapshot_id *sidp, chunknumber_t chunk, int offset, int len, char *buffer) { cow_map_t *cmap = &sidp->sid_cowinfo->cow_map; cow_map_node_t *cmn; struct buf *snapbuf; int error = 0; char *newbuffer; int newlen = 0; int partial = 0; ASSERT(RW_READ_HELD(&sidp->sid_rwlock)); ASSERT(offset + len <= cmap->cmap_chunksz); /* * Check if the chunk number is out of range and if so bail out */ if (chunk >= (cmap->cmap_bmsize * NBBY)) { return (EINVAL); } /* * If the chunk is not a candidate for translation, then the chunk * was not allocated when the snapshot was taken. Since it does * not contain data associated with this snapshot, just return a * zero buffer instead. */ if (isclr(cmap->cmap_candidate, chunk)) { bzero(buffer, len); return (0); } /* * if the chunk is a candidate for translation but a * translation does not exist, then read through to the * original file system. The rwlock is held until the read * completes if it hasn't been translated to make sure the * file system does not translate the block before we * access it. If it has already been translated we don't * need the lock, because the translation will never go away. */ rw_enter(&cmap->cmap_rwlock, RW_READER); if (isclr(cmap->cmap_hastrans, chunk)) { snapbuf = getrbuf(KM_SLEEP); /* * Reading into the buffer saves having to do a copy, * but gets tricky if the request size is not a * multiple of DEV_BSIZE. However, we are filling the * buffer left to right, so future reads will write * over any extra data we might have read. */ partial = len % DEV_BSIZE; snapbuf->b_bcount = len; snapbuf->b_lblkno = lbtodb(chunk * cmap->cmap_chunksz + offset); snapbuf->b_un.b_addr = buffer; snapbuf->b_iodone = NULL; snapbuf->b_proc = NULL; /* i.e. the kernel */ snapbuf->b_flags = B_READ | B_BUSY; snapbuf->b_edev = sidp->sid_fvp->v_vfsp->vfs_dev; if (partial) { /* * Partial block read in progress. * This is bad as modules further down the line * assume buf's are exact multiples of DEV_BSIZE * and we end up with fewer, or zero, bytes read. * To get round this we need to round up to the * nearest full block read and then return only * len bytes. */ newlen = (len - partial) + DEV_BSIZE; newbuffer = kmem_alloc(newlen, KM_SLEEP); snapbuf->b_bcount = newlen; snapbuf->b_un.b_addr = newbuffer; } (void) bdev_strategy(snapbuf); (void) biowait(snapbuf); error = geterror(snapbuf); if (partial) { /* * Partial block read. Now we need to bcopy the * correct number of bytes back into the * supplied buffer, and tidy up our temp * buffer. */ bcopy(newbuffer, buffer, len); kmem_free(newbuffer, newlen); } freerbuf(snapbuf); rw_exit(&cmap->cmap_rwlock); return (error); } /* * finally, if the chunk is a candidate for translation and it * has been translated, then we clone the chunk of the buffer * that was copied aside by the file system. * The cmap_rwlock does not need to be held after we know the * data has already been copied. Once a chunk has been copied * to the backing file, it is stable read only data. */ cmn = transtbl_get(cmap, chunk); /* check whether the data is in memory or in the backing file */ if (cmn != NULL) { ASSERT(cmn->cmn_buf); /* already in memory */ bcopy(cmn->cmn_buf + offset, buffer, len); rw_exit(&cmap->cmap_rwlock); } else { ssize_t resid = len; int bf_index; /* * can cause deadlock with writer if we don't drop the * cmap_rwlock before trying to get the backing store file * vnode rwlock. */ rw_exit(&cmap->cmap_rwlock); bf_index = chunk / cmap->cmap_chunksperbf; /* read buffer from backing file */ error = vn_rdwr(UIO_READ, (sidp->sid_cowinfo->cow_backfile_array)[bf_index], buffer, len, ((chunk % cmap->cmap_chunksperbf) * cmap->cmap_chunksz) + offset, UIO_SYSSPACE, 0, RLIM64_INFINITY, kcred, &resid); } return (error); } /* * snap_print() - snapshot driver print(9E) routine * * prints the device identification string. */ static int snap_print(dev_t dev, char *str) { struct snapshot_id **sidpp; minor_t minor; minor = getminor(dev); sidpp = ddi_get_soft_state(statep, minor); if (sidpp == NULL || *sidpp == NULL) { cmn_err(CE_WARN, "snap_print: could not find state for snapshot %d.", minor); return (ENXIO); } cmn_err(CE_NOTE, "snap_print: snapshot %d: %s", minor, str); return (0); } /* * snap_prop_op() - snapshot driver prop_op(9E) routine * * get 32-bit and 64-bit values for size (character driver) and nblocks * (block driver). */ static int snap_prop_op(dev_t dev, dev_info_t *dip, ddi_prop_op_t prop_op, int flags, char *name, caddr_t valuep, int *lengthp) { int minor; struct snapshot_id **sidpp; dev_t mdev; dev_info_t *mdip; int error; minor = getminor(dev); /* * If this is the control device just check for .conf properties, * if the wildcard DDI_DEV_T_ANY was passed in via the dev_t * just fall back to the defaults. */ if ((minor == SNAP_CTL_MINOR) || (dev == DDI_DEV_T_ANY)) return (ddi_prop_op(dev, dip, prop_op, flags, name, valuep, lengthp)); /* check to see if there is a master device plumbed */ sidpp = ddi_get_soft_state(statep, minor); if (sidpp == NULL || *sidpp == NULL) { cmn_err(CE_WARN, "snap_prop_op: could not find state for " "snapshot %d.", minor); return (DDI_PROP_NOT_FOUND); } if (((*sidpp)->sid_fvp == NULL) || ((*sidpp)->sid_fvp->v_vfsp == NULL)) return (ddi_prop_op(dev, dip, prop_op, flags, name, valuep, lengthp)); /* hold master device and pass operation down */ mdev = (*sidpp)->sid_fvp->v_vfsp->vfs_dev; if (mdip = e_ddi_hold_devi_by_dev(mdev, 0)) { /* get size information from the master device. */ error = cdev_prop_op(mdev, mdip, prop_op, flags, name, valuep, lengthp); ddi_release_devi(mdip); if (error == DDI_PROP_SUCCESS) return (error); } /* master device did not service the request, try framework */ return (ddi_prop_op(dev, dip, prop_op, flags, name, valuep, lengthp)); } /* * snap_ioctl() - snapshot driver ioctl(9E) routine * * only applies to the control device. The control device accepts two * ioctl requests: create a snapshot or delete a snapshot. In either * case, the vnode for the requested file system is extracted, and the * request is passed on to the file system via the same ioctl. The file * system is responsible for doing the things necessary for creating or * destroying a snapshot, including any file system specific operations * that must be performed as well as setting up and deleting the snapshot * state through the fssnap interfaces. */ static int snap_ioctl(dev_t dev, int cmd, intptr_t arg, int mode, cred_t *credp, int *rvalp) { minor_t minor; int error = 0; minor = getminor(dev); if (minor != SNAP_CTL_MINOR) { return (EINVAL); } switch (cmd) { case _FIOSNAPSHOTCREATE: { struct fiosnapcreate fc; struct file *fp; struct vnode *vp; if (ddi_copyin((void *)arg, &fc, sizeof (fc), mode)) return (EFAULT); /* get vnode for file system mount point */ if ((fp = getf(fc.rootfiledesc)) == NULL) return (EBADF); ASSERT(fp->f_vnode); vp = fp->f_vnode; VN_HOLD(vp); releasef(fc.rootfiledesc); /* pass ioctl request to file system */ error = VOP_IOCTL(vp, cmd, arg, 0, credp, rvalp, NULL); VN_RELE(vp); break; } case _FIOSNAPSHOTCREATE_MULTI: { struct fiosnapcreate_multi fc; struct file *fp; struct vnode *vp; if (ddi_copyin((void *)arg, &fc, sizeof (fc), mode)) return (EFAULT); /* get vnode for file system mount point */ if ((fp = getf(fc.rootfiledesc)) == NULL) return (EBADF); ASSERT(fp->f_vnode); vp = fp->f_vnode; VN_HOLD(vp); releasef(fc.rootfiledesc); /* pass ioctl request to file system */ error = VOP_IOCTL(vp, cmd, arg, 0, credp, rvalp, NULL); VN_RELE(vp); break; } case _FIOSNAPSHOTDELETE: { major_t major; struct fiosnapdelete fc; snapshot_id_t *sidp = NULL; snapshot_id_t *sidnextp = NULL; struct file *fp = NULL; struct vnode *vp = NULL; struct vfs *vfsp = NULL; vfsops_t *vfsops = EIO_vfsops; if (ddi_copyin((void *)arg, &fc, sizeof (fc), mode)) return (EFAULT); /* get vnode for file system mount point */ if ((fp = getf(fc.rootfiledesc)) == NULL) return (EBADF); ASSERT(fp->f_vnode); vp = fp->f_vnode; VN_HOLD(vp); releasef(fc.rootfiledesc); /* * Test for two formats of delete and set correct minor/vp: * pseudo device: * fssnap -d [/dev/fssnap/x] * or * mount point: * fssnap -d [/mntpt] * Note that minor is verified to be equal to SNAP_CTL_MINOR * at this point which is an invalid minor number. */ ASSERT(fssnap_dip != NULL); major = ddi_driver_major(fssnap_dip); mutex_enter(&snapshot_mutex); for (sidp = snapshot; sidp != NULL; sidp = sidnextp) { rw_enter(&sidp->sid_rwlock, RW_READER); sidnextp = sidp->sid_next; /* pseudo device: */ if (major == getmajor(vp->v_rdev)) { minor = getminor(vp->v_rdev); if (sidp->sid_snapnumber == (uint_t)minor && sidp->sid_fvp) { VN_RELE(vp); vp = sidp->sid_fvp; VN_HOLD(vp); rw_exit(&sidp->sid_rwlock); break; } /* Mount point: */ } else { if (sidp->sid_fvp == vp) { minor = sidp->sid_snapnumber; rw_exit(&sidp->sid_rwlock); break; } } rw_exit(&sidp->sid_rwlock); } mutex_exit(&snapshot_mutex); /* Verify minor got set correctly above */ if (minor == SNAP_CTL_MINOR) { VN_RELE(vp); return (EINVAL); } dev = makedevice(major, minor); /* * Create dummy vfs entry * to use as a locking semaphore across the IOCTL * for mount in progress cases... */ vfsp = vfs_alloc(KM_SLEEP); VFS_INIT(vfsp, vfsops, NULL); VFS_HOLD(vfsp); vfs_addmip(dev, vfsp); if ((vfs_devmounting(dev, vfsp)) || (vfs_devismounted(dev))) { vfs_delmip(vfsp); VFS_RELE(vfsp); VN_RELE(vp); return (EBUSY); } /* * Nobody mounted but do not release mount in progress lock * until IOCTL complete to prohibit a mount sneaking * in */ error = VOP_IOCTL(vp, cmd, arg, 0, credp, rvalp, NULL); vfs_delmip(vfsp); VFS_RELE(vfsp); VN_RELE(vp); break; } default: cmn_err(CE_WARN, "snap_ioctl: Invalid ioctl cmd %d, minor %d.", cmd, minor); return (EINVAL); } return (error); } /* ************************************************************************ */ /* * Translation Table Routines * * These support routines implement a simple doubly linked list * to keep track of chunks that are currently in memory. The maximum * size of the list is determined by the fssnap_max_mem_chunks variable. * The cmap_rwlock is used to protect the linkage of the list. */ /* * transtbl_add() - add a node to the translation table * * allocates a new node and points it at the buffer passed in. The node * is added to the beginning of the doubly linked list and the head of * the list is moved. The cmap_rwlock must be held as a writer through * this operation. */ static cow_map_node_t * transtbl_add(cow_map_t *cmap, chunknumber_t chunk, caddr_t buf) { cow_map_node_t *cmnode; ASSERT(RW_WRITE_HELD(&cmap->cmap_rwlock)); cmnode = kmem_alloc(sizeof (cow_map_node_t), KM_SLEEP); /* * insert new translations at the beginning so cmn_table is always * the first node. */ cmnode->cmn_chunk = chunk; cmnode->cmn_buf = buf; cmnode->cmn_prev = NULL; cmnode->cmn_next = cmap->cmap_table; if (cmnode->cmn_next) cmnode->cmn_next->cmn_prev = cmnode; cmap->cmap_table = cmnode; return (cmnode); } /* * transtbl_get() - look up a node in the translation table * * called by the snapshot driver to find data that has been translated. * The lookup is done by the chunk number, and the node is returned. * If the node was not found, NULL is returned. */ static cow_map_node_t * transtbl_get(cow_map_t *cmap, chunknumber_t chunk) { cow_map_node_t *cmn; ASSERT(RW_READ_HELD(&cmap->cmap_rwlock)); ASSERT(cmap); /* search the translation table */ for (cmn = cmap->cmap_table; cmn != NULL; cmn = cmn->cmn_next) { if (cmn->cmn_chunk == chunk) return (cmn); } /* not found */ return (NULL); } /* * transtbl_delete() - delete a node from the translation table * * called when a node's data has been written out to disk. The * cmap_rwlock must be held as a writer for this operation. If the node * being deleted is the head of the list, then the head is moved to the * next node. Both the node's data and the node itself are freed. */ static void transtbl_delete(cow_map_t *cmap, cow_map_node_t *cmn) { ASSERT(RW_WRITE_HELD(&cmap->cmap_rwlock)); ASSERT(cmn); ASSERT(cmap->cmap_table); /* if the head of the list is being deleted, then move the head up */ if (cmap->cmap_table == cmn) { ASSERT(cmn->cmn_prev == NULL); cmap->cmap_table = cmn->cmn_next; } /* make previous node's next pointer skip over current node */ if (cmn->cmn_prev != NULL) { ASSERT(cmn->cmn_prev->cmn_next == cmn); cmn->cmn_prev->cmn_next = cmn->cmn_next; } /* make next node's previous pointer skip over current node */ if (cmn->cmn_next != NULL) { ASSERT(cmn->cmn_next->cmn_prev == cmn); cmn->cmn_next->cmn_prev = cmn->cmn_prev; } /* free the data and the node */ ASSERT(cmn->cmn_buf); kmem_free(cmn->cmn_buf, cmap->cmap_chunksz); kmem_free(cmn, sizeof (cow_map_node_t)); } /* * transtbl_free() - free the entire translation table * * called when the snapshot is deleted. This frees all of the nodes in * the translation table (but not the bitmaps). */ static void transtbl_free(cow_map_t *cmap) { cow_map_node_t *curnode; cow_map_node_t *tempnode; for (curnode = cmap->cmap_table; curnode != NULL; curnode = tempnode) { tempnode = curnode->cmn_next; kmem_free(curnode->cmn_buf, cmap->cmap_chunksz); kmem_free(curnode, sizeof (cow_map_node_t)); } } /* ************************************************************************ */ /* * Interface Implementation Routines * * The following functions implement snapshot interface routines that are * called by the file system to create, delete, and use a snapshot. The * interfaces are defined in fssnap_if.c and are filled in by this driver * when it is loaded. This technique allows the file system to depend on * the interface module without having to load the full implementation and * snapshot device drivers. */ /* * fssnap_strategy_impl() - strategy routine called by the file system * * called by the file system to handle copy-on-write when necessary. All * reads and writes that the file system performs should go through this * function. If the file system calls the underlying device's strategy * routine without going through fssnap_strategy() (eg. by calling * bdev_strategy()), the snapshot may not be consistent. * * This function starts by doing significant sanity checking to insure * the snapshot was not deleted out from under it or deleted and then * recreated. To do this, it checks the actual pointer passed into it * (ie. the handle held by the file system). NOTE that the parameter is * a POINTER TO A POINTER to the snapshot id. Once the snapshot id is * locked, it knows things are ok and that this snapshot is really for * this file system. * * If the request is a write, fssnap_translate() is called to determine * whether a copy-on-write is required. If it is a read, the read is * simply passed on to the underlying device. */ static void fssnap_strategy_impl(void *snapshot_id, buf_t *bp) { struct snapshot_id **sidpp; struct snapshot_id *sidp; int error; /* read requests are always passed through */ if (bp->b_flags & B_READ) { (void) bdev_strategy(bp); return; } /* * Because we were not able to take the snapshot read lock BEFORE * checking for a snapshot back in the file system, things may have * drastically changed out from under us. For instance, the snapshot * may have been deleted, deleted and recreated, or worse yet, deleted * for this file system but now the snapshot number is in use by another * file system. * * Having a pointer to the file system's snapshot id pointer allows us * to sanity check most of this, though it assumes the file system is * keeping track of a pointer to the snapshot_id somewhere. */ sidpp = (struct snapshot_id **)snapshot_id; sidp = *sidpp; /* * if this file system's snapshot was disabled, just pass the * request through. */ if (sidp == NULL) { (void) bdev_strategy(bp); return; } /* * Once we have the reader lock the snapshot will not magically go * away. But things may have changed on us before this so double check. */ rw_enter(&sidp->sid_rwlock, RW_READER); /* * if an error was founds somewhere the DELETE flag will be * set to indicate the snapshot should be deleted and no new * translations should occur. */ if (sidp->sid_flags & SID_DELETE) { rw_exit(&sidp->sid_rwlock); (void) fssnap_delete_impl(sidpp); (void) bdev_strategy(bp); return; } /* * If the file system is no longer pointing to the snapshot we were * called with, then it should not attempt to translate this buffer as * it may be going to a snapshot for a different file system. * Even if the file system snapshot pointer is still the same, the * snapshot may have been disabled before we got the reader lock. */ if (sidp != *sidpp || SID_INACTIVE(sidp)) { rw_exit(&sidp->sid_rwlock); (void) bdev_strategy(bp); return; } /* * At this point we're sure the snapshot will not go away while the * reader lock is held, and we are reasonably certain that we are * writing to the correct snapshot. */ if ((error = fssnap_translate(sidpp, bp)) != 0) { /* * fssnap_translate can release the reader lock if it * has to wait for a semaphore. In this case it is possible * for the snapshot to be deleted in this time frame. If this * happens just sent the buf thru to the filesystems device. */ if (sidp != *sidpp || SID_INACTIVE(sidp)) { rw_exit(&sidp->sid_rwlock); (void) bdev_strategy(bp); return; } bioerror(bp, error); biodone(bp); } rw_exit(&sidp->sid_rwlock); } /* * fssnap_translate() - helper function for fssnap_strategy() * * performs the actual copy-on-write for write requests, if required. * This function does the real work of the file system side of things. * * It first checks the candidate bitmap to quickly determine whether any * action is necessary. If the candidate bitmap indicates the chunk was * allocated when the snapshot was created, then it checks to see whether * a translation already exists. If a translation already exists then no * action is required. If the chunk is a candidate for copy-on-write, * and a translation does not already exist, then the chunk is read in * and a node is added to the translation table. * * Once all of the chunks in the request range have been copied (if they * needed to be), then the original request can be satisfied and the old * data can be overwritten. */ static int fssnap_translate(struct snapshot_id **sidpp, struct buf *wbp) { snapshot_id_t *sidp = *sidpp; struct buf *oldbp; /* buffer to store old data in */ struct cow_info *cowp = sidp->sid_cowinfo; cow_map_t *cmap = &cowp->cow_map; cow_map_node_t *cmn; chunknumber_t cowchunk, startchunk, endchunk; int error; int throttle_write = 0; /* make sure the snapshot is active */ ASSERT(RW_READ_HELD(&sidp->sid_rwlock)); startchunk = dbtocowchunk(cmap, wbp->b_lblkno); endchunk = dbtocowchunk(cmap, wbp->b_lblkno + ((wbp->b_bcount-1) >> DEV_BSHIFT)); /* * Do not throttle the writes of the fssnap taskq thread and * the log roll (trans_roll) thread. Furthermore the writes to * the on-disk log are also not subject to throttling. * The fssnap_write_taskq thread's write can block on the throttling * semaphore which leads to self-deadlock as this same thread * releases the throttling semaphore after completing the IO. * If the trans_roll thread's write is throttled then we can deadlock * because the fssnap_taskq_thread which releases the throttling * semaphore can block waiting for log space which can only be * released by the trans_roll thread. */ throttle_write = !(taskq_member(cowp->cow_taskq, curthread) || tsd_get(bypass_snapshot_throttle_key)); /* * Iterate through all chunks covered by this write and perform the * copy-aside if necessary. Once all chunks have been safely * stowed away, the new data may be written in a single sweep. * * For each chunk in the range, the following sequence is performed: * - Is the chunk a candidate for translation? * o If not, then no translation is necessary, continue * - If it is a candidate, then does it already have a translation? * o If so, then no translation is necessary, continue * - If it is a candidate, but does not yet have a translation, * then read the old data and schedule an asynchronous taskq * to write the old data to the backing file. * * Once this has been performed over the entire range of chunks, then * it is safe to overwrite the data that is there. * * Note that no lock is required to check the candidate bitmap because * it never changes once the snapshot is created. The reader lock is * taken to check the hastrans bitmap since it may change. If it * turns out a copy is required, then the lock is upgraded to a * writer, and the bitmap is re-checked as it may have changed while * the lock was released. Finally, the write lock is held while * reading the old data to make sure it is not translated out from * under us. * * This locking mechanism should be sufficient to handle multiple * threads writing to overlapping chunks simultaneously. */ for (cowchunk = startchunk; cowchunk <= endchunk; cowchunk++) { /* * If the cowchunk is outside of the range of our * candidate maps, then simply break out of the * loop and pass the I/O through to bdev_strategy. * This would occur if the file system has grown * larger since the snapshot was taken. */ if (cowchunk >= (cmap->cmap_bmsize * NBBY)) break; /* * If no disk blocks were allocated in this chunk when the * snapshot was created then no copy-on-write will be * required. Since this bitmap is read-only no locks are * necessary. */ if (isclr(cmap->cmap_candidate, cowchunk)) { continue; } /* * If a translation already exists, the data can be written * through since the old data has already been saved off. */ if (isset(cmap->cmap_hastrans, cowchunk)) { continue; } /* * Throttle translations if there are too many outstanding * chunks in memory. The semaphore is sema_v'd by the taskq. * * You can't keep the sid_rwlock if you would go to sleep. * This will result in deadlock when someone tries to delete * the snapshot (wants the sid_rwlock as a writer, but can't * get it). */ if (throttle_write) { if (sema_tryp(&cmap->cmap_throttle_sem) == 0) { rw_exit(&sidp->sid_rwlock); atomic_inc_32(&cmap->cmap_waiters); sema_p(&cmap->cmap_throttle_sem); atomic_dec_32(&cmap->cmap_waiters); rw_enter(&sidp->sid_rwlock, RW_READER); /* * Now since we released the sid_rwlock the state may * have transitioned underneath us. so check that again. */ if (sidp != *sidpp || SID_INACTIVE(sidp)) { sema_v(&cmap->cmap_throttle_sem); return (ENXIO); } } } /* * Acquire the lock as a writer and check to see if a * translation has been added in the meantime. */ rw_enter(&cmap->cmap_rwlock, RW_WRITER); if (isset(cmap->cmap_hastrans, cowchunk)) { if (throttle_write) sema_v(&cmap->cmap_throttle_sem); rw_exit(&cmap->cmap_rwlock); continue; /* go to the next chunk */ } /* * read a full chunk of data from the requested offset rounded * down to the nearest chunk size. */ oldbp = getrbuf(KM_SLEEP); oldbp->b_lblkno = cowchunktodb(cmap, cowchunk); oldbp->b_edev = wbp->b_edev; oldbp->b_bcount = cmap->cmap_chunksz; oldbp->b_bufsize = cmap->cmap_chunksz; oldbp->b_iodone = NULL; oldbp->b_proc = NULL; oldbp->b_flags = B_READ; oldbp->b_un.b_addr = kmem_alloc(cmap->cmap_chunksz, KM_SLEEP); (void) bdev_strategy(oldbp); (void) biowait(oldbp); /* * It's ok to bail in the middle of translating the range * because the extra copy-asides will not hurt anything * (except by using extra space in the backing store). */ if ((error = geterror(oldbp)) != 0) { cmn_err(CE_WARN, "fssnap_translate: error reading " "old data for snapshot %d, chunk %llu, disk block " "%lld, size %lu, error %d.", sidp->sid_snapnumber, cowchunk, oldbp->b_lblkno, oldbp->b_bcount, error); kmem_free(oldbp->b_un.b_addr, cmap->cmap_chunksz); freerbuf(oldbp); rw_exit(&cmap->cmap_rwlock); if (throttle_write) sema_v(&cmap->cmap_throttle_sem); return (error); } /* * add the node to the translation table and save a reference * to pass to the taskq for writing out to the backing file */ cmn = transtbl_add(cmap, cowchunk, oldbp->b_un.b_addr); freerbuf(oldbp); /* * Add a reference to the snapshot id so the lower level * processing (ie. the taskq) can get back to the state * information. */ cmn->cmn_sid = sidp; cmn->release_sem = throttle_write; setbit(cmap->cmap_hastrans, cowchunk); rw_exit(&cmap->cmap_rwlock); /* * schedule the asynchronous write to the backing file */ if (cowp->cow_backfile_array != NULL) (void) taskq_dispatch(cowp->cow_taskq, fssnap_write_taskq, cmn, TQ_SLEEP); } /* * Write new data in place of the old data. At this point all of the * chunks touched by this write have been copied aside and so the new * data can be written out all at once. */ (void) bdev_strategy(wbp); return (0); } /* * fssnap_write_taskq() - write in-memory translations to the backing file * * writes in-memory translations to the backing file asynchronously. A * task is dispatched each time a new translation is created. The task * writes the data to the backing file and removes it from the memory * list. The throttling semaphore is released only if the particular * translation was throttled in fssnap_translate. */ static void fssnap_write_taskq(void *arg) { cow_map_node_t *cmn = (cow_map_node_t *)arg; snapshot_id_t *sidp = cmn->cmn_sid; cow_info_t *cowp = sidp->sid_cowinfo; cow_map_t *cmap = &cowp->cow_map; int error; int bf_index; int release_sem = cmn->release_sem; /* * The sid_rwlock does not need to be held here because the taskqs * are destroyed explicitly by fssnap_delete (with the sid_rwlock * held as a writer). taskq_destroy() will flush all of the tasks * out before fssnap_delete frees up all of the structures. */ /* if the snapshot was disabled from under us, drop the request. */ rw_enter(&sidp->sid_rwlock, RW_READER); if (SID_INACTIVE(sidp)) { rw_exit(&sidp->sid_rwlock); if (release_sem) sema_v(&cmap->cmap_throttle_sem); return; } rw_exit(&sidp->sid_rwlock); atomic_inc_64((uint64_t *)&cmap->cmap_nchunks); if ((cmap->cmap_maxsize != 0) && ((cmap->cmap_nchunks * cmap->cmap_chunksz) > cmap->cmap_maxsize)) { cmn_err(CE_WARN, "fssnap_write_taskq: snapshot %d (%s) has " "reached the maximum backing file size specified (%llu " "bytes) and will be deleted.", sidp->sid_snapnumber, (char *)cowp->cow_kstat_mntpt->ks_data, cmap->cmap_maxsize); if (release_sem) sema_v(&cmap->cmap_throttle_sem); atomic_or_uint(&sidp->sid_flags, SID_DELETE); return; } /* perform the write */ bf_index = cmn->cmn_chunk / cmap->cmap_chunksperbf; if (error = vn_rdwr(UIO_WRITE, (cowp->cow_backfile_array)[bf_index], cmn->cmn_buf, cmap->cmap_chunksz, (cmn->cmn_chunk % cmap->cmap_chunksperbf) * cmap->cmap_chunksz, UIO_SYSSPACE, 0, RLIM64_INFINITY, kcred, (ssize_t *)NULL)) { cmn_err(CE_WARN, "fssnap_write_taskq: error writing to " "backing file. DELETING SNAPSHOT %d, backing file path " "%s, offset %llu bytes, error %d.", sidp->sid_snapnumber, (char *)cowp->cow_kstat_bfname->ks_data, cmn->cmn_chunk * cmap->cmap_chunksz, error); if (release_sem) sema_v(&cmap->cmap_throttle_sem); atomic_or_uint(&sidp->sid_flags, SID_DELETE); return; } /* * now remove the node and buffer from memory */ rw_enter(&cmap->cmap_rwlock, RW_WRITER); transtbl_delete(cmap, cmn); rw_exit(&cmap->cmap_rwlock); /* Allow more translations */ if (release_sem) sema_v(&cmap->cmap_throttle_sem); } /* * fssnap_create_impl() - called from the file system to create a new snapshot * * allocates and initializes the structures needed for a new snapshot. * This is called by the file system when it receives an ioctl request to * create a new snapshot. An unused snapshot identifier is either found * or created, and eventually returned as the opaque handle the file * system will use to identify this snapshot. The snapshot number * associated with the snapshot identifier is the same as the minor * number for the snapshot device that is used to access that snapshot. * * The snapshot can not be used until the candidate bitmap is populated * by the file system (see fssnap_set_candidate_impl()), and the file * system finishes the setup process by calling fssnap_create_done(). * Nearly all of the snapshot locks are held for the duration of the * create, and are not released until fssnap_create_done is called(). */ static void * fssnap_create_impl(chunknumber_t nchunks, uint_t chunksz, u_offset_t maxsize, struct vnode *fsvp, int backfilecount, struct vnode **bfvpp, char *backpath, u_offset_t max_backfile_size) { refstr_t *mountpoint; char taskqname[50]; struct cow_info *cowp; struct cow_map *cmap; struct snapshot_id *sidp; int lastsnap; /* * Sanity check the parameters we care about * (we don't care about the informational parameters) */ if ((nchunks == 0) || ((chunksz % DEV_BSIZE) != 0) || (bfvpp == NULL)) { return (NULL); } /* * Look for unused snapshot identifiers. Snapshot ids are never * freed, but deleted snapshot ids will be recycled as needed. */ mutex_enter(&snapshot_mutex); findagain: lastsnap = 0; for (sidp = snapshot; sidp != NULL; sidp = sidp->sid_next) { if (sidp->sid_snapnumber > lastsnap) lastsnap = sidp->sid_snapnumber; /* * The sid_rwlock is taken as a reader initially so that * activity on each snapshot is not stalled while searching * for a free snapshot id. */ rw_enter(&sidp->sid_rwlock, RW_READER); /* * If the snapshot has been deleted and nobody is using the * snapshot device than we can reuse this snapshot_id. If * the snapshot is marked to be deleted (SID_DELETE), then * it hasn't been deleted yet so don't reuse it. */ if (SID_AVAILABLE(sidp)) break; /* This spot is unused, so take it */ rw_exit(&sidp->sid_rwlock); } /* * add a new snapshot identifier if there are no deleted * entries. Since it doesn't matter what order the entries * are in we can just add it to the beginning of the list. */ if (sidp) { if (rw_tryupgrade(&sidp->sid_rwlock) == 0) { /* someone else grabbed it as a writer, try again */ rw_exit(&sidp->sid_rwlock); goto findagain; } } else { /* Create a new node if we didn't find an unused one */ sidp = kmem_alloc(sizeof (struct snapshot_id), KM_SLEEP); rw_init(&sidp->sid_rwlock, NULL, RW_DEFAULT, NULL); rw_enter(&sidp->sid_rwlock, RW_WRITER); sidp->sid_snapnumber = (snapshot == NULL) ? 0 : lastsnap + 1; sidp->sid_cowinfo = NULL; sidp->sid_flags = 0; sidp->sid_next = snapshot; snapshot = sidp; } ASSERT(RW_WRITE_HELD(&sidp->sid_rwlock)); ASSERT(sidp->sid_cowinfo == NULL); ASSERT(sidp->sid_snapnumber <= (lastsnap + 1)); sidp->sid_flags |= SID_CREATING; /* The root vnode is held until snap_delete_impl() is called */ VN_HOLD(fsvp); sidp->sid_fvp = fsvp; num_snapshots++; /* allocate and initialize structures */ cowp = kmem_zalloc(sizeof (struct cow_info), KM_SLEEP); cowp->cow_backfile_array = bfvpp; cowp->cow_backcount = backfilecount; cowp->cow_backfile_sz = max_backfile_size; /* * Initialize task queues for this snapshot. Only a small number * of threads are required because they will be serialized on the * backing file's reader/writer lock anyway. */ (void) snprintf(taskqname, sizeof (taskqname), "%s_taskq_%d", snapname, sidp->sid_snapnumber); cowp->cow_taskq = taskq_create(taskqname, fssnap_taskq_nthreads, minclsyspri, 1, fssnap_taskq_maxtasks, 0); /* don't allow tasks to start until after everything is ready */ taskq_suspend(cowp->cow_taskq); /* initialize translation table */ cmap = &cowp->cow_map; rw_init(&cmap->cmap_rwlock, NULL, RW_DEFAULT, NULL); rw_enter(&cmap->cmap_rwlock, RW_WRITER); sema_init(&cmap->cmap_throttle_sem, fssnap_max_mem_chunks, NULL, SEMA_DEFAULT, NULL); cmap->cmap_chunksz = chunksz; cmap->cmap_maxsize = maxsize; cmap->cmap_chunksperbf = max_backfile_size / chunksz; /* * allocate one bit per chunk for the bitmaps, round up */ cmap->cmap_bmsize = (nchunks + (NBBY - 1)) / NBBY; cmap->cmap_hastrans = kmem_zalloc(cmap->cmap_bmsize, KM_SLEEP); cmap->cmap_candidate = kmem_zalloc(cmap->cmap_bmsize, KM_SLEEP); sidp->sid_cowinfo = cowp; /* initialize kstats for this snapshot */ mountpoint = vfs_getmntpoint(fsvp->v_vfsp); fssnap_create_kstats(sidp, sidp->sid_snapnumber, refstr_value(mountpoint), backpath); refstr_rele(mountpoint); mutex_exit(&snapshot_mutex); /* * return with snapshot id rwlock held as a writer until * fssnap_create_done is called */ return (sidp); } /* * fssnap_set_candidate_impl() - mark a chunk as a candidate for copy-on-write * * sets a bit in the candidate bitmap that indicates that a chunk is a * candidate for copy-on-write. Typically, chunks that are allocated on * the file system at the time the snapshot is taken are candidates, * while chunks that have no allocated data do not need to be copied. * Chunks containing metadata must be marked as candidates as well. */ static void fssnap_set_candidate_impl(void *snapshot_id, chunknumber_t chunknumber) { struct snapshot_id *sid = snapshot_id; struct cow_info *cowp = sid->sid_cowinfo; struct cow_map *cmap = &cowp->cow_map; /* simple bitmap operation for now */ ASSERT(chunknumber < (cmap->cmap_bmsize * NBBY)); setbit(cmap->cmap_candidate, chunknumber); } /* * fssnap_is_candidate_impl() - check whether a chunk is a candidate * * returns 0 if the chunk is not a candidate and 1 if the chunk is a * candidate. This can be used by the file system to change behavior for * chunks that might induce a copy-on-write. The offset is specified in * bytes since the chunk size may not be known by the file system. */ static int fssnap_is_candidate_impl(void *snapshot_id, u_offset_t off) { struct snapshot_id *sid = snapshot_id; struct cow_info *cowp = sid->sid_cowinfo; struct cow_map *cmap = &cowp->cow_map; ulong_t chunknumber = off / cmap->cmap_chunksz; /* simple bitmap operation for now */ ASSERT(chunknumber < (cmap->cmap_bmsize * NBBY)); return (isset(cmap->cmap_candidate, chunknumber)); } /* * fssnap_create_done_impl() - complete the snapshot setup process * * called when the file system is done populating the candidate bitmap * and it is ready to start using the snapshot. This routine releases * the snapshot locks, allows taskq tasks to start processing, and * creates the device minor nodes associated with the snapshot. */ static int fssnap_create_done_impl(void *snapshot_id) { struct snapshot_id **sidpp, *sidp = snapshot_id; struct cow_info *cowp; struct cow_map *cmap; int snapnumber = -1; char name[20]; /* sid rwlock and cmap rwlock should be taken from fssnap_create */ ASSERT(sidp); ASSERT(RW_WRITE_HELD(&sidp->sid_rwlock)); ASSERT(sidp->sid_cowinfo); cowp = sidp->sid_cowinfo; cmap = &cowp->cow_map; ASSERT(RW_WRITE_HELD(&cmap->cmap_rwlock)); sidp->sid_flags &= ~(SID_CREATING | SID_DISABLED); snapnumber = sidp->sid_snapnumber; /* allocate state structure and find new snapshot id */ if (ddi_soft_state_zalloc(statep, snapnumber) != DDI_SUCCESS) { cmn_err(CE_WARN, "snap_ioctl: create: could not allocate " "state for snapshot %d.", snapnumber); snapnumber = -1; goto out; } sidpp = ddi_get_soft_state(statep, snapnumber); *sidpp = sidp; /* create minor node based on snapshot number */ ASSERT(fssnap_dip != NULL); (void) snprintf(name, sizeof (name), "%d", snapnumber); if (ddi_create_minor_node(fssnap_dip, name, S_IFBLK, snapnumber, DDI_PSEUDO, 0) != DDI_SUCCESS) { cmn_err(CE_WARN, "snap_ioctl: could not create " "block minor node for snapshot %d.", snapnumber); snapnumber = -1; goto out; } (void) snprintf(name, sizeof (name), "%d,raw", snapnumber); if (ddi_create_minor_node(fssnap_dip, name, S_IFCHR, snapnumber, DDI_PSEUDO, 0) != DDI_SUCCESS) { cmn_err(CE_WARN, "snap_ioctl: could not create " "character minor node for snapshot %d.", snapnumber); snapnumber = -1; } out: rw_exit(&sidp->sid_rwlock); rw_exit(&cmap->cmap_rwlock); /* let the taskq threads start processing */ taskq_resume(cowp->cow_taskq); return (snapnumber); } /* * fssnap_delete_impl() - delete a snapshot * * used when a snapshot is no longer needed. This is called by the file * system when it receives an ioctl request to delete a snapshot. It is * also called internally when error conditions such as disk full, errors * writing to the backing file, or backing file maxsize exceeded occur. * If the snapshot device is busy when the delete request is received, * all state will be deleted except for the soft state and device files * associated with the snapshot; they will be deleted when the snapshot * device is closed. * * NOTE this function takes a POINTER TO A POINTER to the snapshot id, * and expects to be able to set the handle held by the file system to * NULL. This depends on the file system checking that variable for NULL * before calling fssnap_strategy(). */ static int fssnap_delete_impl(void *snapshot_id) { struct snapshot_id **sidpp = (struct snapshot_id **)snapshot_id; struct snapshot_id *sidp; struct snapshot_id **statesidpp; struct cow_info *cowp; struct cow_map *cmap; char name[20]; int snapnumber = -1; vnode_t **vpp; /* * sidp is guaranteed to be valid if sidpp is valid because * the snapshot list is append-only. */ if (sidpp == NULL) { return (-1); } sidp = *sidpp; rw_enter(&sidp->sid_rwlock, RW_WRITER); ASSERT(RW_WRITE_HELD(&sidp->sid_rwlock)); /* * double check that the snapshot is still valid for THIS file system */ if (*sidpp == NULL) { rw_exit(&sidp->sid_rwlock); return (-1); } /* * Now we know the snapshot is still valid and will not go away * because we have the write lock. Once the state is transitioned * to "disabling", the sid_rwlock can be released. Any pending I/O * waiting for the lock as a reader will check for this state and * abort without touching data that may be getting freed. */ sidp->sid_flags |= SID_DISABLING; if (sidp->sid_flags & SID_DELETE) { cmn_err(CE_WARN, "Snapshot %d automatically deleted.", sidp->sid_snapnumber); sidp->sid_flags &= ~(SID_DELETE); } /* * This is pointing into file system specific data! The assumption is * that fssnap_strategy() gets called from the file system based on * whether this reference to the snapshot_id is NULL or not. So * setting this to NULL should disable snapshots for the file system. */ *sidpp = NULL; /* remove cowinfo */ cowp = sidp->sid_cowinfo; if (cowp == NULL) { rw_exit(&sidp->sid_rwlock); return (-1); } rw_exit(&sidp->sid_rwlock); /* destroy task queues first so they don't reference freed data. */ if (cowp->cow_taskq) { taskq_destroy(cowp->cow_taskq); cowp->cow_taskq = NULL; } if (cowp->cow_backfile_array != NULL) { for (vpp = cowp->cow_backfile_array; *vpp; vpp++) VN_RELE(*vpp); kmem_free(cowp->cow_backfile_array, (cowp->cow_backcount + 1) * sizeof (vnode_t *)); cowp->cow_backfile_array = NULL; } sidp->sid_cowinfo = NULL; /* remove cmap */ cmap = &cowp->cow_map; ASSERT(cmap); if (cmap->cmap_candidate) kmem_free(cmap->cmap_candidate, cmap->cmap_bmsize); if (cmap->cmap_hastrans) kmem_free(cmap->cmap_hastrans, cmap->cmap_bmsize); if (cmap->cmap_table) transtbl_free(&cowp->cow_map); rw_destroy(&cmap->cmap_rwlock); while (cmap->cmap_waiters) { sema_p(&cmap->cmap_throttle_sem); sema_v(&cmap->cmap_throttle_sem); } sema_destroy(&cmap->cmap_throttle_sem); /* remove kstats */ fssnap_delete_kstats(cowp); kmem_free(cowp, sizeof (struct cow_info)); statesidpp = ddi_get_soft_state(statep, sidp->sid_snapnumber); if (statesidpp == NULL || *statesidpp == NULL) { cmn_err(CE_WARN, "fssnap_delete_impl: could not find state for snapshot %d.", sidp->sid_snapnumber); } ASSERT(*statesidpp == sidp); /* * Leave the node in the list marked DISABLED so it can be reused * and avoid many race conditions. Return the snapshot number * that was deleted. */ mutex_enter(&snapshot_mutex); rw_enter(&sidp->sid_rwlock, RW_WRITER); sidp->sid_flags &= ~(SID_DISABLING); sidp->sid_flags |= SID_DISABLED; VN_RELE(sidp->sid_fvp); sidp->sid_fvp = NULL; snapnumber = sidp->sid_snapnumber; /* * If the snapshot is not busy, free the device info now. Otherwise * the device nodes are freed in snap_close() when the device is * closed. The sid will not be reused until the device is not busy. */ if (SID_AVAILABLE(sidp)) { /* remove the device nodes */ ASSERT(fssnap_dip != NULL); (void) snprintf(name, sizeof (name), "%d", sidp->sid_snapnumber); ddi_remove_minor_node(fssnap_dip, name); (void) snprintf(name, sizeof (name), "%d,raw", sidp->sid_snapnumber); ddi_remove_minor_node(fssnap_dip, name); /* delete the state structure */ ddi_soft_state_free(statep, sidp->sid_snapnumber); num_snapshots--; } mutex_exit(&snapshot_mutex); rw_exit(&sidp->sid_rwlock); return (snapnumber); } /* * fssnap_create_kstats() - allocate and initialize snapshot kstats * */ static void fssnap_create_kstats(snapshot_id_t *sidp, int snapnum, const char *mountpoint, const char *backfilename) { kstat_t *num, *mntpoint, *bfname; kstat_named_t *hw; struct cow_info *cowp = sidp->sid_cowinfo; struct cow_kstat_num *stats; /* update the high water mark */ if (fssnap_highwater_kstat == NULL) { cmn_err(CE_WARN, "fssnap_create_kstats: failed to lookup " "high water mark kstat."); return; } hw = (kstat_named_t *)fssnap_highwater_kstat->ks_data; if (hw->value.ui32 < snapnum) hw->value.ui32 = snapnum; /* initialize the mount point kstat */ kstat_delete_byname(snapname, snapnum, FSSNAP_KSTAT_MNTPT); if (mountpoint != NULL) { mntpoint = kstat_create(snapname, snapnum, FSSNAP_KSTAT_MNTPT, "misc", KSTAT_TYPE_RAW, strlen(mountpoint) + 1, 0); if (mntpoint == NULL) { cowp->cow_kstat_mntpt = NULL; cmn_err(CE_WARN, "fssnap_create_kstats: failed to " "create mount point kstat"); } else { (void) strncpy(mntpoint->ks_data, mountpoint, strlen(mountpoint)); cowp->cow_kstat_mntpt = mntpoint; kstat_install(mntpoint); } } else { cowp->cow_kstat_mntpt = NULL; cmn_err(CE_WARN, "fssnap_create_kstats: mount point not " "specified."); } /* initialize the backing file kstat */ kstat_delete_byname(snapname, snapnum, FSSNAP_KSTAT_BFNAME); if (backfilename == NULL) { cowp->cow_kstat_bfname = NULL; } else { bfname = kstat_create(snapname, snapnum, FSSNAP_KSTAT_BFNAME, "misc", KSTAT_TYPE_RAW, strlen(backfilename) + 1, 0); if (bfname != NULL) { (void) strncpy(bfname->ks_data, backfilename, strlen(backfilename)); cowp->cow_kstat_bfname = bfname; kstat_install(bfname); } else { cowp->cow_kstat_bfname = NULL; cmn_err(CE_WARN, "fssnap_create_kstats: failed to " "create backing file name kstat"); } } /* initialize numeric kstats */ kstat_delete_byname(snapname, snapnum, FSSNAP_KSTAT_NUM); num = kstat_create(snapname, snapnum, FSSNAP_KSTAT_NUM, "misc", KSTAT_TYPE_NAMED, sizeof (struct cow_kstat_num) / sizeof (kstat_named_t), 0); if (num == NULL) { cmn_err(CE_WARN, "fssnap_create_kstats: failed to create " "numeric kstats"); cowp->cow_kstat_num = NULL; return; } cowp->cow_kstat_num = num; stats = num->ks_data; num->ks_update = fssnap_update_kstat_num; num->ks_private = sidp; kstat_named_init(&stats->ckn_state, FSSNAP_KSTAT_NUM_STATE, KSTAT_DATA_INT32); kstat_named_init(&stats->ckn_bfsize, FSSNAP_KSTAT_NUM_BFSIZE, KSTAT_DATA_UINT64); kstat_named_init(&stats->ckn_maxsize, FSSNAP_KSTAT_NUM_MAXSIZE, KSTAT_DATA_UINT64); kstat_named_init(&stats->ckn_createtime, FSSNAP_KSTAT_NUM_CREATETIME, KSTAT_DATA_LONG); kstat_named_init(&stats->ckn_chunksize, FSSNAP_KSTAT_NUM_CHUNKSIZE, KSTAT_DATA_UINT32); /* initialize the static kstats */ stats->ckn_chunksize.value.ui32 = cowp->cow_map.cmap_chunksz; stats->ckn_maxsize.value.ui64 = cowp->cow_map.cmap_maxsize; stats->ckn_createtime.value.l = gethrestime_sec(); kstat_install(num); } /* * fssnap_update_kstat_num() - update a numerical snapshot kstat value * */ int fssnap_update_kstat_num(kstat_t *ksp, int rw) { snapshot_id_t *sidp = (snapshot_id_t *)ksp->ks_private; struct cow_info *cowp = sidp->sid_cowinfo; struct cow_kstat_num *stats = ksp->ks_data; if (rw == KSTAT_WRITE) return (EACCES); /* state */ if (sidp->sid_flags & SID_CREATING) stats->ckn_state.value.i32 = COWSTATE_CREATING; else if (SID_INACTIVE(sidp)) stats->ckn_state.value.i32 = COWSTATE_DISABLED; else if (SID_BUSY(sidp)) stats->ckn_state.value.i32 = COWSTATE_ACTIVE; else stats->ckn_state.value.i32 = COWSTATE_IDLE; /* bfsize */ stats->ckn_bfsize.value.ui64 = cowp->cow_map.cmap_nchunks * cowp->cow_map.cmap_chunksz; return (0); } /* * fssnap_delete_kstats() - deallocate snapshot kstats * */ void fssnap_delete_kstats(struct cow_info *cowp) { if (cowp->cow_kstat_num != NULL) { kstat_delete(cowp->cow_kstat_num); cowp->cow_kstat_num = NULL; } if (cowp->cow_kstat_mntpt != NULL) { kstat_delete(cowp->cow_kstat_mntpt); cowp->cow_kstat_mntpt = NULL; } if (cowp->cow_kstat_bfname != NULL) { kstat_delete(cowp->cow_kstat_bfname); cowp->cow_kstat_bfname = NULL; } }