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exfat: add cache option for __exfat_ent_get

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When multiple entries are obtained consecutively, these entries are mostly
stored adjacent to each other. this patch introduces a "last" parameter to
cache the last opened buffer head, and reuse it when possible, which
reduces the number of sb_bread() calls.

When the passed parameter "last" is NULL, it means cache option is
disabled, the behavior unchanged as it was.

Signed-off-by: Chi Zhiling <chizhiling@kylinos.cn>
Reviewed-by: Yuezhang Mo <Yuezhang.Mo@sony.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
This commit is contained in:
Chi Zhiling 2026-01-14 20:12:37 +08:00 committed by Namjae Jeon
parent 0914882bdd
commit 967288e9a6
1 changed files with 13 additions and 7 deletions
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20
fs/exfat/fatent.c
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@ -36,18 +36,23 @@ static int exfat_mirror_bh(struct super_block *sb, sector_t sec,
}
static int __exfat_ent_get(struct super_block *sb, unsigned int loc,
unsigned int *content)
unsigned int *content, struct buffer_head **last)
{
unsigned int off;
sector_t sec;
struct buffer_head *bh;
struct buffer_head *bh = last ? *last : NULL;
sec = FAT_ENT_OFFSET_SECTOR(sb, loc);
off = FAT_ENT_OFFSET_BYTE_IN_SECTOR(sb, loc);
bh = sb_bread(sb, sec);
if (!bh)
return -EIO;
if (!bh || bh->b_blocknr != sec || !buffer_uptodate(bh)) {
brelse(bh);
bh = sb_bread(sb, sec);
if (last)
*last = bh;
if (unlikely(!bh))
return -EIO;
}
*content = le32_to_cpu(*(__le32 *)(&bh->b_data[off]));
@ -55,7 +60,8 @@ static int __exfat_ent_get(struct super_block *sb, unsigned int loc,
if (*content > EXFAT_BAD_CLUSTER)
*content = EXFAT_EOF_CLUSTER;
brelse(bh);
if (!last)
brelse(bh);
return 0;
}
@ -95,7 +101,7 @@ int exfat_ent_get(struct super_block *sb, unsigned int loc,
return -EIO;
}
err = __exfat_ent_get(sb, loc, content);
err = __exfat_ent_get(sb, loc, content, NULL);
if (err) {
exfat_fs_error_ratelimit(sb,
"failed to access to FAT (entry 0x%08x, err:%d)",