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btrfs: reduce the size of compressed_bio

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The member compressed_bio::compressed_len can be replaced by the bio
size, as we always submit the full compressed data without any partial
read/write.

Furthermore we already have enough ASSERT()s making sure the bio size
matches the ordered extent or the extent map.

This saves 8 bytes from compressed_bio:

Before:

struct compressed_bio {
        u64                        start;                /*     0     8 */
        unsigned int               len;                  /*     8     4 */
        unsigned int               compressed_len;       /*    12     4 */
        u8                         compress_type;        /*    16     1 */
        bool                       writeback;            /*    17     1 */

        /* XXX 6 bytes hole, try to pack */

        struct btrfs_bio *         orig_bbio;            /*    24     8 */
        struct btrfs_bio           bbio __attribute__((__aligned__(8))); /*    32   304 */

        /* XXX last struct has 1 bit hole */

        /* size: 336, cachelines: 6, members: 7 */
        /* sum members: 330, holes: 1, sum holes: 6 */
        /* member types with bit holes: 1, total: 1 */
        /* forced alignments: 1 */
        /* last cacheline: 16 bytes */
} __attribute__((__aligned__(8)));

After:

 struct compressed_bio {
        u64                        start;                /*     0     8 */
        unsigned int               len;                  /*     8     4 */
        u8                         compress_type;        /*    12     1 */
        bool                       writeback;            /*    13     1 */

        /* XXX 2 bytes hole, try to pack */

        struct btrfs_bio *         orig_bbio;            /*    16     8 */
        struct btrfs_bio           bbio __attribute__((__aligned__(8))); /*    24   304 */

        /* XXX last struct has 1 bit hole */

        /* size: 328, cachelines: 6, members: 6 */
        /* sum members: 326, holes: 1, sum holes: 2 */
        /* member types with bit holes: 1, total: 1 */
        /* forced alignments: 1 */
        /* last cacheline: 8 bytes */
} __attribute__((__aligned__(8)));

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Qu Wenruo 2026-02-20 14:11:51 +10:30 committed by David Sterba
parent c4bc2dd32c
commit b05342fe47
5 changed files with 6 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
fs/btrfs/compression.c
View File

@ -330,7 +330,6 @@ void btrfs_submit_compressed_write(struct btrfs_ordered_extent *ordered,
cb->start = ordered->file_offset;
cb->len = ordered->num_bytes;
ASSERT(cb->bbio.bio.bi_iter.bi_size == ordered->disk_num_bytes);
cb->compressed_len = ordered->disk_num_bytes;
cb->bbio.bio.bi_iter.bi_sector = ordered->disk_bytenr >> SECTOR_SHIFT;
cb->bbio.ordered = ordered;
@ -560,7 +559,6 @@ void btrfs_submit_compressed_read(struct btrfs_bio *bbio)
em_start = em->start;
cb->len = bbio->bio.bi_iter.bi_size;
cb->compressed_len = compressed_len;
cb->compress_type = btrfs_extent_map_compression(em);
cb->orig_bbio = bbio;
cb->bbio.csum_search_commit_root = bbio->csum_search_commit_root;

3
fs/btrfs/compression.h
View File

@ -48,9 +48,6 @@ struct compressed_bio {
/* Number of bytes in the inode we're working on */
unsigned int len;
/* Number of bytes on disk */
unsigned int compressed_len;
/* The compression algorithm for this bio */
u8 compress_type;

7
fs/btrfs/lzo.c
View File

@ -431,6 +431,7 @@ int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
struct workspace *workspace = list_entry(ws, struct workspace, list);
struct btrfs_fs_info *fs_info = cb->bbio.inode->root->fs_info;
const u32 sectorsize = fs_info->sectorsize;
const u32 compressed_len = bio_get_size(&cb->bbio.bio);
struct folio_iter fi;
char *kaddr;
int ret;
@ -460,14 +461,14 @@ int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
* and all sectors should be used.
* If this happens, it means the compressed extent is corrupted.
*/
if (unlikely(len_in > min_t(size_t, BTRFS_MAX_COMPRESSED, cb->compressed_len) ||
round_up(len_in, sectorsize) < cb->compressed_len)) {
if (unlikely(len_in > min_t(size_t, BTRFS_MAX_COMPRESSED, compressed_len) ||
round_up(len_in, sectorsize) < compressed_len)) {
struct btrfs_inode *inode = cb->bbio.inode;
btrfs_err(fs_info,
"lzo header invalid, root %llu inode %llu offset %llu lzo len %u compressed len %u",
btrfs_root_id(inode->root), btrfs_ino(inode),
cb->start, len_in, cb->compressed_len);
cb->start, len_in, compressed_len);
return -EUCLEAN;
}

2
fs/btrfs/zlib.c
View File

@ -351,7 +351,7 @@ int zlib_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
int wbits = MAX_WBITS;
char *data_in;
size_t total_out = 0;
size_t srclen = cb->compressed_len;
const size_t srclen = bio_get_size(&cb->bbio.bio);
unsigned long buf_start;
bio_first_folio(&fi, &cb->bbio.bio, 0);

2
fs/btrfs/zstd.c
View File

@ -587,7 +587,7 @@ int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
struct btrfs_fs_info *fs_info = cb_to_fs_info(cb);
struct workspace *workspace = list_entry(ws, struct workspace, list);
struct folio_iter fi;
size_t srclen = cb->compressed_len;
size_t srclen = bio_get_size(&cb->bbio.bio);
zstd_dstream *stream;
int ret = 0;
const u32 blocksize = fs_info->sectorsize;