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authorJan Kara <jack@suse.cz>2023-04-11 15:10:19 +0300
committerTheodore Ts'o <tytso@mit.edu>2023-05-08 04:11:18 +0300
commit949f95ff39bf188e594e7ecd8e29b82eb108f5bf (patch)
tree44699efa34673153e6884287fc77fa96e08de5cd /fs
parentfa08a7b61dff8a4df11ff1e84abfc214b487caf7 (diff)
downloadlinux-949f95ff39bf188e594e7ecd8e29b82eb108f5bf.tar.xz
ext4: fix lockdep warning when enabling MMP
When we enable MMP in ext4_multi_mount_protect() during mount or remount, we end up calling sb_start_write() from write_mmp_block(). This triggers lockdep warning because freeze protection ranks above s_umount semaphore we are holding during mount / remount. The problem is harmless because we are guaranteed the filesystem is not frozen during mount / remount but still let's fix the warning by not grabbing freeze protection from ext4_multi_mount_protect(). Cc: stable@kernel.org Reported-by: syzbot+6b7df7d5506b32467149@syzkaller.appspotmail.com Link: https://syzkaller.appspot.com/bug?id=ab7e5b6f400b7778d46f01841422e5718fb81843 Signed-off-by: Jan Kara <jack@suse.cz> Reviewed-by: Christian Brauner <brauner@kernel.org> Link: https://lore.kernel.org/r/20230411121019.21940-1-jack@suse.cz Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to 'fs')
-rw-r--r--fs/ext4/mmp.c30
1 files changed, 21 insertions, 9 deletions
diff --git a/fs/ext4/mmp.c b/fs/ext4/mmp.c
index 4022bc713421..0aaf38ffcb6e 100644
--- a/fs/ext4/mmp.c
+++ b/fs/ext4/mmp.c
@@ -39,28 +39,36 @@ static void ext4_mmp_csum_set(struct super_block *sb, struct mmp_struct *mmp)
* Write the MMP block using REQ_SYNC to try to get the block on-disk
* faster.
*/
-static int write_mmp_block(struct super_block *sb, struct buffer_head *bh)
+static int write_mmp_block_thawed(struct super_block *sb,
+ struct buffer_head *bh)
{
struct mmp_struct *mmp = (struct mmp_struct *)(bh->b_data);
- /*
- * We protect against freezing so that we don't create dirty buffers
- * on frozen filesystem.
- */
- sb_start_write(sb);
ext4_mmp_csum_set(sb, mmp);
lock_buffer(bh);
bh->b_end_io = end_buffer_write_sync;
get_bh(bh);
submit_bh(REQ_OP_WRITE | REQ_SYNC | REQ_META | REQ_PRIO, bh);
wait_on_buffer(bh);
- sb_end_write(sb);
if (unlikely(!buffer_uptodate(bh)))
return -EIO;
-
return 0;
}
+static int write_mmp_block(struct super_block *sb, struct buffer_head *bh)
+{
+ int err;
+
+ /*
+ * We protect against freezing so that we don't create dirty buffers
+ * on frozen filesystem.
+ */
+ sb_start_write(sb);
+ err = write_mmp_block_thawed(sb, bh);
+ sb_end_write(sb);
+ return err;
+}
+
/*
* Read the MMP block. It _must_ be read from disk and hence we clear the
* uptodate flag on the buffer.
@@ -344,7 +352,11 @@ skip:
seq = mmp_new_seq();
mmp->mmp_seq = cpu_to_le32(seq);
- retval = write_mmp_block(sb, bh);
+ /*
+ * On mount / remount we are protected against fs freezing (by s_umount
+ * semaphore) and grabbing freeze protection upsets lockdep
+ */
+ retval = write_mmp_block_thawed(sb, bh);
if (retval)
goto failed;