[RFC PATCH v1 4/6] exfat: lock FAT2 buffer while copying mirrored FAT entries
Chi Zhiling <[email protected]>
| Newsgroups | dev.linux.lists.exfat,org.kernel.vger.linux-kernel |
|---|---|
| Message-ID | <[email protected]> |
From: Chi Zhiling <[email protected]> exfat_mirror_bh() updates the FAT2 buffer without serializing the copy against writeback. Once s_lock is converted to a read-write lock, multiple read-side operations may run concurrently with writeback. This can allow writeback to observe a partially updated FAT2 block. Lock the destination buffer while copying the FAT entry data to serialize the update with writeback and prevent torn FAT2 writes. Signed-off-by: Chi Zhiling <[email protected]> --- fs/exfat/fatent.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/fs/exfat/fatent.c b/fs/exfat/fatent.c index 2db959669563..f6ad2825ad19 100644 --- a/fs/exfat/fatent.c +++ b/fs/exfat/fatent.c @@ -24,7 +24,10 @@ static int exfat_mirror_bh(struct super_block *sb, struct buffer_head *bh) c_bh = sb_getblk(sb, sec2); if (!c_bh) return -ENOMEM; + /* Serialize the copy with writeback to avoid a torn FAT2 write */ + lock_buffer(c_bh); memcpy(c_bh->b_data, bh->b_data, sb->s_blocksize); + unlock_buffer(c_bh); err = exfat_update_bh(c_bh, sb->s_flags & SB_SYNCHRONOUS); brelse(c_bh); } -- 2.53.0