fs/ext4/ext4_extents.h

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * Copyright (c) 2003-2006, Cluster File Systems, Inc, info@clusterfs.com
0004  * Written by Alex Tomas <alex@clusterfs.com>
0005  */
0006
0007 #ifndef _EXT4_EXTENTS
0008 #define _EXT4_EXTENTS
0009
0010 #include "ext4.h"
0011
0012 /*
0013  * With AGGRESSIVE_TEST defined, the capacity of index/leaf blocks
0014  * becomes very small, so index split, in-depth growing and
0015  * other hard changes happen much more often.
0016  * This is for debug purposes only.
0017  */
0018 #define AGGRESSIVE_TEST_
0019
0020 /*
0021  * With EXTENTS_STATS defined, the number of blocks and extents
0022  * are collected in the truncate path. They'll be shown at
0023  * umount time.
0024  */
0025 #define EXTENTS_STATS__
0026
0027 /*
0028  * If CHECK_BINSEARCH is defined, then the results of the binary search
0029  * will also be checked by linear search.
0030  */
0031 #define CHECK_BINSEARCH__
0032
0033 /*
0034  * If EXT_STATS is defined then stats numbers are collected.
0035  * These number will be displayed at umount time.
0036  */
0037 #define EXT_STATS_
0038
0039
0040 /*
0041  * ext4_inode has i_block array (60 bytes total).
0042  * The first 12 bytes store ext4_extent_header;
0043  * the remainder stores an array of ext4_extent.
0044  * For non-inode extent blocks, ext4_extent_tail
0045  * follows the array.
0046  */
0047
0048 /*
0049  * This is the extent tail on-disk structure.
0050  * All other extent structures are 12 bytes long.  It turns out that
0051  * block_size % 12 >= 4 for at least all powers of 2 greater than 512, which
0052  * covers all valid ext4 block sizes.  Therefore, this tail structure can be
0053  * crammed into the end of the block without having to rebalance the tree.
0054  */
0055 struct ext4_extent_tail {
0056     __le32  et_checksum;    /* crc32c(uuid+inum+extent_block) */
0057 };
0058
0059 /*
0060  * This is the extent on-disk structure.
0061  * It's used at the bottom of the tree.
0062  */
0063 struct ext4_extent {
0064     __le32  ee_block;   /* first logical block extent covers */
0065     __le16  ee_len;     /* number of blocks covered by extent */
0066     __le16  ee_start_hi;    /* high 16 bits of physical block */
0067     __le32  ee_start_lo;    /* low 32 bits of physical block */
0068 };
0069
0070 /*
0071  * This is index on-disk structure.
0072  * It's used at all the levels except the bottom.
0073  */
0074 struct ext4_extent_idx {
0075     __le32  ei_block;   /* index covers logical blocks from 'block' */
0076     __le32  ei_leaf_lo; /* pointer to the physical block of the next *
0077                  * level. leaf or next index could be there */
0078     __le16  ei_leaf_hi; /* high 16 bits of physical block */
0079     __u16   ei_unused;
0080 };
0081
0082 /*
0083  * Each block (leaves and indexes), even inode-stored has header.
0084  */
0085 struct ext4_extent_header {
0086     __le16  eh_magic;   /* probably will support different formats */
0087     __le16  eh_entries; /* number of valid entries */
0088     __le16  eh_max;     /* capacity of store in entries */
0089     __le16  eh_depth;   /* has tree real underlying blocks? */
0090     __le32  eh_generation;  /* generation of the tree */
0091 };
0092
0093 #define EXT4_EXT_MAGIC      cpu_to_le16(0xf30a)
0094 #define EXT4_MAX_EXTENT_DEPTH 5
0095
0096 #define EXT4_EXTENT_TAIL_OFFSET(hdr) \
0097     (sizeof(struct ext4_extent_header) + \
0098      (sizeof(struct ext4_extent) * le16_to_cpu((hdr)->eh_max)))
0099
0100 static inline struct ext4_extent_tail *
0101 find_ext4_extent_tail(struct ext4_extent_header *eh)
0102 {
0103     return (struct ext4_extent_tail *)(((void *)eh) +
0104                        EXT4_EXTENT_TAIL_OFFSET(eh));
0105 }
0106
0107 /*
0108  * Array of ext4_ext_path contains path to some extent.
0109  * Creation/lookup routines use it for traversal/splitting/etc.
0110  * Truncate uses it to simulate recursive walking.
0111  */
0112 struct ext4_ext_path {
0113     ext4_fsblk_t            p_block;
0114     __u16               p_depth;
0115     __u16               p_maxdepth;
0116     struct ext4_extent      *p_ext;
0117     struct ext4_extent_idx      *p_idx;
0118     struct ext4_extent_header   *p_hdr;
0119     struct buffer_head      *p_bh;
0120 };
0121
0122 /*
0123  * Used to record a portion of a cluster found at the beginning or end
0124  * of an extent while traversing the extent tree during space removal.
0125  * A partial cluster may be removed if it does not contain blocks shared
0126  * with extents that aren't being deleted (tofree state).  Otherwise,
0127  * it cannot be removed (nofree state).
0128  */
0129 struct partial_cluster {
0130     ext4_fsblk_t pclu;  /* physical cluster number */
0131     ext4_lblk_t lblk;   /* logical block number within logical cluster */
0132     enum {initial, tofree, nofree} state;
0133 };
0134
0135 /*
0136  * structure for external API
0137  */
0138
0139 /*
0140  * EXT_INIT_MAX_LEN is the maximum number of blocks we can have in an
0141  * initialized extent. This is 2^15 and not (2^16 - 1), since we use the
0142  * MSB of ee_len field in the extent datastructure to signify if this
0143  * particular extent is an initialized extent or an unwritten (i.e.
0144  * preallocated).
0145  * EXT_UNWRITTEN_MAX_LEN is the maximum number of blocks we can have in an
0146  * unwritten extent.
0147  * If ee_len is <= 0x8000, it is an initialized extent. Otherwise, it is an
0148  * unwritten one. In other words, if MSB of ee_len is set, it is an
0149  * unwritten extent with only one special scenario when ee_len = 0x8000.
0150  * In this case we can not have an unwritten extent of zero length and
0151  * thus we make it as a special case of initialized extent with 0x8000 length.
0152  * This way we get better extent-to-group alignment for initialized extents.
0153  * Hence, the maximum number of blocks we can have in an *initialized*
0154  * extent is 2^15 (32768) and in an *unwritten* extent is 2^15-1 (32767).
0155  */
0156 #define EXT_INIT_MAX_LEN    (1UL << 15)
0157 #define EXT_UNWRITTEN_MAX_LEN   (EXT_INIT_MAX_LEN - 1)
0158
0159
0160 #define EXT_FIRST_EXTENT(__hdr__) \
0161     ((struct ext4_extent *) (((char *) (__hdr__)) +     \
0162                  sizeof(struct ext4_extent_header)))
0163 #define EXT_FIRST_INDEX(__hdr__) \
0164     ((struct ext4_extent_idx *) (((char *) (__hdr__)) + \
0165                      sizeof(struct ext4_extent_header)))
0166 #define EXT_HAS_FREE_INDEX(__path__) \
0167     (le16_to_cpu((__path__)->p_hdr->eh_entries) \
0168                      < le16_to_cpu((__path__)->p_hdr->eh_max))
0169 #define EXT_LAST_EXTENT(__hdr__) \
0170     (EXT_FIRST_EXTENT((__hdr__)) + le16_to_cpu((__hdr__)->eh_entries) - 1)
0171 #define EXT_LAST_INDEX(__hdr__) \
0172     (EXT_FIRST_INDEX((__hdr__)) + le16_to_cpu((__hdr__)->eh_entries) - 1)
0173 #define EXT_MAX_EXTENT(__hdr__) \
0174     ((le16_to_cpu((__hdr__)->eh_max)) ? \
0175     ((EXT_FIRST_EXTENT((__hdr__)) + le16_to_cpu((__hdr__)->eh_max) - 1)) \
0176                     : NULL)
0177 #define EXT_MAX_INDEX(__hdr__) \
0178     ((le16_to_cpu((__hdr__)->eh_max)) ? \
0179     ((EXT_FIRST_INDEX((__hdr__)) + le16_to_cpu((__hdr__)->eh_max) - 1)) \
0180                     : NULL)
0181
0182 static inline struct ext4_extent_header *ext_inode_hdr(struct inode *inode)
0183 {
0184     return (struct ext4_extent_header *) EXT4_I(inode)->i_data;
0185 }
0186
0187 static inline struct ext4_extent_header *ext_block_hdr(struct buffer_head *bh)
0188 {
0189     return (struct ext4_extent_header *) bh->b_data;
0190 }
0191
0192 static inline unsigned short ext_depth(struct inode *inode)
0193 {
0194     return le16_to_cpu(ext_inode_hdr(inode)->eh_depth);
0195 }
0196
0197 static inline void ext4_ext_mark_unwritten(struct ext4_extent *ext)
0198 {
0199     /* We can not have an unwritten extent of zero length! */
0200     BUG_ON((le16_to_cpu(ext->ee_len) & ~EXT_INIT_MAX_LEN) == 0);
0201     ext->ee_len |= cpu_to_le16(EXT_INIT_MAX_LEN);
0202 }
0203
0204 static inline int ext4_ext_is_unwritten(struct ext4_extent *ext)
0205 {
0206     /* Extent with ee_len of 0x8000 is treated as an initialized extent */
0207     return (le16_to_cpu(ext->ee_len) > EXT_INIT_MAX_LEN);
0208 }
0209
0210 static inline int ext4_ext_get_actual_len(struct ext4_extent *ext)
0211 {
0212     return (le16_to_cpu(ext->ee_len) <= EXT_INIT_MAX_LEN ?
0213         le16_to_cpu(ext->ee_len) :
0214         (le16_to_cpu(ext->ee_len) - EXT_INIT_MAX_LEN));
0215 }
0216
0217 static inline void ext4_ext_mark_initialized(struct ext4_extent *ext)
0218 {
0219     ext->ee_len = cpu_to_le16(ext4_ext_get_actual_len(ext));
0220 }
0221
0222 /*
0223  * ext4_ext_pblock:
0224  * combine low and high parts of physical block number into ext4_fsblk_t
0225  */
0226 static inline ext4_fsblk_t ext4_ext_pblock(struct ext4_extent *ex)
0227 {
0228     ext4_fsblk_t block;
0229
0230     block = le32_to_cpu(ex->ee_start_lo);
0231     block |= ((ext4_fsblk_t) le16_to_cpu(ex->ee_start_hi) << 31) << 1;
0232     return block;
0233 }
0234
0235 /*
0236  * ext4_idx_pblock:
0237  * combine low and high parts of a leaf physical block number into ext4_fsblk_t
0238  */
0239 static inline ext4_fsblk_t ext4_idx_pblock(struct ext4_extent_idx *ix)
0240 {
0241     ext4_fsblk_t block;
0242
0243     block = le32_to_cpu(ix->ei_leaf_lo);
0244     block |= ((ext4_fsblk_t) le16_to_cpu(ix->ei_leaf_hi) << 31) << 1;
0245     return block;
0246 }
0247
0248 /*
0249  * ext4_ext_store_pblock:
0250  * stores a large physical block number into an extent struct,
0251  * breaking it into parts
0252  */
0253 static inline void ext4_ext_store_pblock(struct ext4_extent *ex,
0254                      ext4_fsblk_t pb)
0255 {
0256     ex->ee_start_lo = cpu_to_le32((unsigned long) (pb & 0xffffffff));
0257     ex->ee_start_hi = cpu_to_le16((unsigned long) ((pb >> 31) >> 1) &
0258                       0xffff);
0259 }
0260
0261 /*
0262  * ext4_idx_store_pblock:
0263  * stores a large physical block number into an index struct,
0264  * breaking it into parts
0265  */
0266 static inline void ext4_idx_store_pblock(struct ext4_extent_idx *ix,
0267                      ext4_fsblk_t pb)
0268 {
0269     ix->ei_leaf_lo = cpu_to_le32((unsigned long) (pb & 0xffffffff));
0270     ix->ei_leaf_hi = cpu_to_le16((unsigned long) ((pb >> 31) >> 1) &
0271                      0xffff);
0272 }
0273
0274 #endif /* _EXT4_EXTENTS */
0275