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 *
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
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
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
192 static inline unsigned short ext_depth(struct inode *inode)
193 {
194 return le16_to_cpu(ext_inode_hdr(inode)->eh_depth);
195 }
196
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
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
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
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 */
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 */
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 */
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 */
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
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