Commit 967288e9 authored by Chi Zhiling's avatar Chi Zhiling Committed by Namjae Jeon
Browse files

exfat: add cache option for __exfat_ent_get 



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: default avatarChi Zhiling <chizhiling@kylinos.cn>
Reviewed-by: default avatarYuezhang Mo <Yuezhang.Mo@sony.com>
Signed-off-by: default avatarNamjae Jeon <linkinjeon@kernel.org>
parent 0914882b

fs/exfat/fatent.c

+13 −7
Original line number Diff line number Diff line
@@ -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);



	if (!bh || bh->b_blocknr != sec || !buffer_uptodate(bh)) {

		brelse(bh);

		bh = sb_bread(sb, sec);

	if (!bh)

		if (last)

			*last = bh;

		if (unlikely(!bh))

			return -EIO;

	}



	*content = le32_to_cpu(*(__le32 *)(&bh->b_data[off]));
@@ -55,6 +60,7 @@ static int __exfat_ent_get(struct super_block *sb, unsigned int loc, 
	if (*content > EXFAT_BAD_CLUSTER)

		*content = EXFAT_EOF_CLUSTER;



	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)",