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ext4: fix lockdep warning when enabling MMP
[ Upstream commit 949f95ff39
]
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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
parent
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commit
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1 changed files with 21 additions and 9 deletions
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@ -39,28 +39,36 @@ static void ext4_mmp_csum_set(struct super_block *sb, struct mmp_struct *mmp)
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* Write the MMP block using REQ_SYNC to try to get the block on-disk
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* Write the MMP block using REQ_SYNC to try to get the block on-disk
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* faster.
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* faster.
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*/
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*/
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static int write_mmp_block(struct super_block *sb, struct buffer_head *bh)
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static int write_mmp_block_thawed(struct super_block *sb,
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struct buffer_head *bh)
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{
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{
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struct mmp_struct *mmp = (struct mmp_struct *)(bh->b_data);
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struct mmp_struct *mmp = (struct mmp_struct *)(bh->b_data);
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/*
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* We protect against freezing so that we don't create dirty buffers
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* on frozen filesystem.
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*/
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sb_start_write(sb);
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ext4_mmp_csum_set(sb, mmp);
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ext4_mmp_csum_set(sb, mmp);
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lock_buffer(bh);
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lock_buffer(bh);
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bh->b_end_io = end_buffer_write_sync;
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bh->b_end_io = end_buffer_write_sync;
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get_bh(bh);
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get_bh(bh);
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submit_bh(REQ_OP_WRITE, REQ_SYNC | REQ_META | REQ_PRIO, bh);
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submit_bh(REQ_OP_WRITE, REQ_SYNC | REQ_META | REQ_PRIO, bh);
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wait_on_buffer(bh);
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wait_on_buffer(bh);
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sb_end_write(sb);
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if (unlikely(!buffer_uptodate(bh)))
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if (unlikely(!buffer_uptodate(bh)))
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return -EIO;
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return -EIO;
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return 0;
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return 0;
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}
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}
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static int write_mmp_block(struct super_block *sb, struct buffer_head *bh)
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{
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int err;
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/*
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* We protect against freezing so that we don't create dirty buffers
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* on frozen filesystem.
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*/
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sb_start_write(sb);
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err = write_mmp_block_thawed(sb, bh);
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sb_end_write(sb);
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return err;
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}
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/*
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/*
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* Read the MMP block. It _must_ be read from disk and hence we clear the
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* Read the MMP block. It _must_ be read from disk and hence we clear the
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* uptodate flag on the buffer.
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* uptodate flag on the buffer.
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@ -352,7 +360,11 @@ int ext4_multi_mount_protect(struct super_block *sb,
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seq = mmp_new_seq();
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seq = mmp_new_seq();
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mmp->mmp_seq = cpu_to_le32(seq);
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mmp->mmp_seq = cpu_to_le32(seq);
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retval = write_mmp_block(sb, bh);
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/*
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* On mount / remount we are protected against fs freezing (by s_umount
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* semaphore) and grabbing freeze protection upsets lockdep
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*/
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retval = write_mmp_block_thawed(sb, bh);
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if (retval)
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if (retval)
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goto failed;
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goto failed;
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