xref: /linux/fs/ext4/ext4_extents.h (revision 762f99f4f3cb41a775b5157dd761217beba65873)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright (c) 2003-2006, Cluster File Systems, Inc, info@clusterfs.com
4  * Written by Alex Tomas <alex@clusterfs.com>
5  */
6 
7 #ifndef _EXT4_EXTENTS
8 #define _EXT4_EXTENTS
9 
10 #include "ext4.h"
11 
12 /*
13  * With AGGRESSIVE_TEST defined, the capacity of index/leaf blocks
14  * becomes very small, so index split, in-depth growing and
15  * other hard changes happen much more often.
16  * This is for debug purposes only.
17  */
18 #define AGGRESSIVE_TEST_
19 
20 /*
21  * With EXTENTS_STATS defined, the number of blocks and extents
22  * are collected in the truncate path. They'll be shown at
23  * umount time.
24  */
25 #define EXTENTS_STATS__
26 
27 /*
28  * If CHECK_BINSEARCH is defined, then the results of the binary search
29  * will also be checked by linear search.
30  */
31 #define CHECK_BINSEARCH__
32 
33 /*
34  * If EXT_STATS is defined then stats numbers are collected.
35  * These number will be displayed at umount time.
36  */
37 #define EXT_STATS_
38 
39 
40 /*
41  * ext4_inode has i_block array (60 bytes total).
42  * The first 12 bytes store ext4_extent_header;
43  * the remainder stores an array of ext4_extent.
44  * For non-inode extent blocks, ext4_extent_tail
45  * follows the array.
46  */
47 
48 /*
49  * This is the extent tail on-disk structure.
50  * All other extent structures are 12 bytes long.  It turns out that
51  * block_size % 12 >= 4 for at least all powers of 2 greater than 512, which
52  * covers all valid ext4 block sizes.  Therefore, this tail structure can be
53  * crammed into the end of the block without having to rebalance the tree.
54  */
55 struct ext4_extent_tail {
56 	__le32	et_checksum;	/* crc32c(uuid+inum+extent_block) */
57 };
58 
59 /*
60  * This is the extent on-disk structure.
61  * It's used at the bottom of the tree.
62  */
63 struct ext4_extent {
64 	__le32	ee_block;	/* first logical block extent covers */
65 	__le16	ee_len;		/* number of blocks covered by extent */
66 	__le16	ee_start_hi;	/* high 16 bits of physical block */
67 	__le32	ee_start_lo;	/* low 32 bits of physical block */
68 };
69 
70 /*
71  * This is index on-disk structure.
72  * It's used at all the levels except the bottom.
73  */
74 struct ext4_extent_idx {
75 	__le32	ei_block;	/* index covers logical blocks from 'block' */
76 	__le32	ei_leaf_lo;	/* pointer to the physical block of the next *
77 				 * level. leaf or next index could be there */
78 	__le16	ei_leaf_hi;	/* high 16 bits of physical block */
79 	__u16	ei_unused;
80 };
81 
82 /*
83  * Each block (leaves and indexes), even inode-stored has header.
84  */
85 struct ext4_extent_header {
86 	__le16	eh_magic;	/* probably will support different formats */
87 	__le16	eh_entries;	/* number of valid entries */
88 	__le16	eh_max;		/* capacity of store in entries */
89 	__le16	eh_depth;	/* has tree real underlying blocks? */
90 	__le32	eh_generation;	/* generation of the tree */
91 };
92 
93 #define EXT4_EXT_MAGIC		cpu_to_le16(0xf30a)
94 #define EXT4_MAX_EXTENT_DEPTH 5
95 
96 #define EXT4_EXTENT_TAIL_OFFSET(hdr) \
97 	(sizeof(struct ext4_extent_header) + \
98 	 (sizeof(struct ext4_extent) * le16_to_cpu((hdr)->eh_max)))
99 
100 static inline struct ext4_extent_tail *
find_ext4_extent_tail(struct ext4_extent_header * eh)101 find_ext4_extent_tail(struct ext4_extent_header *eh)
102 {
103 	return (struct ext4_extent_tail *)(((void *)eh) +
104 					   EXT4_EXTENT_TAIL_OFFSET(eh));
105 }
106 
107 /*
108  * Array of ext4_ext_path contains path to some extent.
109  * Creation/lookup routines use it for traversal/splitting/etc.
110  * Truncate uses it to simulate recursive walking.
111  */
112 struct ext4_ext_path {
113 	ext4_fsblk_t			p_block;
114 	__u16				p_depth;
115 	__u16				p_maxdepth;
116 	struct ext4_extent		*p_ext;
117 	struct ext4_extent_idx		*p_idx;
118 	struct ext4_extent_header	*p_hdr;
119 	struct buffer_head		*p_bh;
120 };
121 
122 /*
123  * Used to record a portion of a cluster found at the beginning or end
124  * of an extent while traversing the extent tree during space removal.
125  * A partial cluster may be removed if it does not contain blocks shared
126  * with extents that aren't being deleted (tofree state).  Otherwise,
127  * it cannot be removed (nofree state).
128  */
129 struct partial_cluster {
130 	ext4_fsblk_t pclu;  /* physical cluster number */
131 	ext4_lblk_t lblk;   /* logical block number within logical cluster */
132 	enum {initial, tofree, nofree} state;
133 };
134 
135 /*
136  * structure for external API
137  */
138 
139 /*
140  * EXT_INIT_MAX_LEN is the maximum number of blocks we can have in an
141  * initialized extent. This is 2^15 and not (2^16 - 1), since we use the
142  * MSB of ee_len field in the extent datastructure to signify if this
143  * particular extent is an initialized extent or an unwritten (i.e.
144  * preallocated).
145  * EXT_UNWRITTEN_MAX_LEN is the maximum number of blocks we can have in an
146  * unwritten extent.
147  * If ee_len is <= 0x8000, it is an initialized extent. Otherwise, it is an
148  * unwritten one. In other words, if MSB of ee_len is set, it is an
149  * unwritten extent with only one special scenario when ee_len = 0x8000.
150  * In this case we can not have an unwritten extent of zero length and
151  * thus we make it as a special case of initialized extent with 0x8000 length.
152  * This way we get better extent-to-group alignment for initialized extents.
153  * Hence, the maximum number of blocks we can have in an *initialized*
154  * extent is 2^15 (32768) and in an *unwritten* extent is 2^15-1 (32767).
155  */
156 #define EXT_INIT_MAX_LEN	(1UL << 15)
157 #define EXT_UNWRITTEN_MAX_LEN	(EXT_INIT_MAX_LEN - 1)
158 
159 
160 #define EXT_FIRST_EXTENT(__hdr__) \
161 	((struct ext4_extent *) (((char *) (__hdr__)) +		\
162 				 sizeof(struct ext4_extent_header)))
163 #define EXT_FIRST_INDEX(__hdr__) \
164 	((struct ext4_extent_idx *) (((char *) (__hdr__)) +	\
165 				     sizeof(struct ext4_extent_header)))
166 #define EXT_HAS_FREE_INDEX(__path__) \
167 	(le16_to_cpu((__path__)->p_hdr->eh_entries) \
168 				     < le16_to_cpu((__path__)->p_hdr->eh_max))
169 #define EXT_LAST_EXTENT(__hdr__) \
170 	(EXT_FIRST_EXTENT((__hdr__)) + le16_to_cpu((__hdr__)->eh_entries) - 1)
171 #define EXT_LAST_INDEX(__hdr__) \
172 	(EXT_FIRST_INDEX((__hdr__)) + le16_to_cpu((__hdr__)->eh_entries) - 1)
173 #define EXT_MAX_EXTENT(__hdr__)	\
174 	((le16_to_cpu((__hdr__)->eh_max)) ? \
175 	((EXT_FIRST_EXTENT((__hdr__)) + le16_to_cpu((__hdr__)->eh_max) - 1)) \
176 					: NULL)
177 #define EXT_MAX_INDEX(__hdr__) \
178 	((le16_to_cpu((__hdr__)->eh_max)) ? \
179 	((EXT_FIRST_INDEX((__hdr__)) + le16_to_cpu((__hdr__)->eh_max) - 1)) \
180 					: NULL)
181 
ext_inode_hdr(struct inode * inode)182 static inline struct ext4_extent_header *ext_inode_hdr(struct inode *inode)
183 {
184 	return (struct ext4_extent_header *) EXT4_I(inode)->i_data;
185 }
186 
ext_block_hdr(struct buffer_head * bh)187 static inline struct ext4_extent_header *ext_block_hdr(struct buffer_head *bh)
188 {
189 	return (struct ext4_extent_header *) bh->b_data;
190 }
191 
ext_depth(struct inode * inode)192 static inline unsigned short ext_depth(struct inode *inode)
193 {
194 	return le16_to_cpu(ext_inode_hdr(inode)->eh_depth);
195 }
196 
ext4_ext_mark_unwritten(struct ext4_extent * ext)197 static inline void ext4_ext_mark_unwritten(struct ext4_extent *ext)
198 {
199 	/* We can not have an unwritten extent of zero length! */
200 	BUG_ON((le16_to_cpu(ext->ee_len) & ~EXT_INIT_MAX_LEN) == 0);
201 	ext->ee_len |= cpu_to_le16(EXT_INIT_MAX_LEN);
202 }
203 
ext4_ext_is_unwritten(struct ext4_extent * ext)204 static inline int ext4_ext_is_unwritten(struct ext4_extent *ext)
205 {
206 	/* Extent with ee_len of 0x8000 is treated as an initialized extent */
207 	return (le16_to_cpu(ext->ee_len) > EXT_INIT_MAX_LEN);
208 }
209 
ext4_ext_get_actual_len(struct ext4_extent * ext)210 static inline int ext4_ext_get_actual_len(struct ext4_extent *ext)
211 {
212 	return (le16_to_cpu(ext->ee_len) <= EXT_INIT_MAX_LEN ?
213 		le16_to_cpu(ext->ee_len) :
214 		(le16_to_cpu(ext->ee_len) - EXT_INIT_MAX_LEN));
215 }
216 
ext4_ext_mark_initialized(struct ext4_extent * ext)217 static inline void ext4_ext_mark_initialized(struct ext4_extent *ext)
218 {
219 	ext->ee_len = cpu_to_le16(ext4_ext_get_actual_len(ext));
220 }
221 
222 /*
223  * ext4_ext_pblock:
224  * combine low and high parts of physical block number into ext4_fsblk_t
225  */
ext4_ext_pblock(struct ext4_extent * ex)226 static inline ext4_fsblk_t ext4_ext_pblock(struct ext4_extent *ex)
227 {
228 	ext4_fsblk_t block;
229 
230 	block = le32_to_cpu(ex->ee_start_lo);
231 	block |= ((ext4_fsblk_t) le16_to_cpu(ex->ee_start_hi) << 31) << 1;
232 	return block;
233 }
234 
235 /*
236  * ext4_idx_pblock:
237  * combine low and high parts of a leaf physical block number into ext4_fsblk_t
238  */
ext4_idx_pblock(struct ext4_extent_idx * ix)239 static inline ext4_fsblk_t ext4_idx_pblock(struct ext4_extent_idx *ix)
240 {
241 	ext4_fsblk_t block;
242 
243 	block = le32_to_cpu(ix->ei_leaf_lo);
244 	block |= ((ext4_fsblk_t) le16_to_cpu(ix->ei_leaf_hi) << 31) << 1;
245 	return block;
246 }
247 
248 /*
249  * ext4_ext_store_pblock:
250  * stores a large physical block number into an extent struct,
251  * breaking it into parts
252  */
ext4_ext_store_pblock(struct ext4_extent * ex,ext4_fsblk_t pb)253 static inline void ext4_ext_store_pblock(struct ext4_extent *ex,
254 					 ext4_fsblk_t pb)
255 {
256 	ex->ee_start_lo = cpu_to_le32((unsigned long) (pb & 0xffffffff));
257 	ex->ee_start_hi = cpu_to_le16((unsigned long) ((pb >> 31) >> 1) &
258 				      0xffff);
259 }
260 
261 /*
262  * ext4_idx_store_pblock:
263  * stores a large physical block number into an index struct,
264  * breaking it into parts
265  */
ext4_idx_store_pblock(struct ext4_extent_idx * ix,ext4_fsblk_t pb)266 static inline void ext4_idx_store_pblock(struct ext4_extent_idx *ix,
267 					 ext4_fsblk_t pb)
268 {
269 	ix->ei_leaf_lo = cpu_to_le32((unsigned long) (pb & 0xffffffff));
270 	ix->ei_leaf_hi = cpu_to_le16((unsigned long) ((pb >> 31) >> 1) &
271 				     0xffff);
272 }
273 
274 #endif /* _EXT4_EXTENTS */
275 
276