On Thu, Dec 1, 2016 at 9:45 PM, Liu Bo <bo.li.liu@xxxxxxxxxx> wrote:
> While checking INODE_REF/INODE_EXTREF for a corner case, we may acquire a
> different inode's log_mutex with holding the current inode's log_mutex, and
> lockdep has complained this with a possilble deadlock warning.
>
> Fix this by using mutex_lock_nested() when processing the other inode's
> log_mutex.
>
> Signed-off-by: Liu Bo <bo.li.liu@xxxxxxxxxx>
Reviewed-by: Filipe Manana <fdmanana@xxxxxxxx>
Thanks, it works and it's simple.
> ---
> fs/btrfs/tree-log.c | 12 +++++++++---
> 1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
> index 3d33c4e..e961451 100644
> --- a/fs/btrfs/tree-log.c
> +++ b/fs/btrfs/tree-log.c
> @@ -37,6 +37,7 @@
> */
> #define LOG_INODE_ALL 0
> #define LOG_INODE_EXISTS 1
> +#define LOG_OTHER_INODE 2
>
> /*
> * directory trouble cases
> @@ -4624,7 +4625,7 @@ static int btrfs_log_inode(struct btrfs_trans_handle *trans,
> if (S_ISDIR(inode->i_mode) ||
> (!test_bit(BTRFS_INODE_NEEDS_FULL_SYNC,
> &BTRFS_I(inode)->runtime_flags) &&
> - inode_only == LOG_INODE_EXISTS))
> + inode_only >= LOG_INODE_EXISTS))
> max_key.type = BTRFS_XATTR_ITEM_KEY;
> else
> max_key.type = (u8)-1;
> @@ -4648,7 +4649,12 @@ static int btrfs_log_inode(struct btrfs_trans_handle *trans,
> return ret;
> }
>
> - mutex_lock(&BTRFS_I(inode)->log_mutex);
> + if (inode_only == LOG_OTHER_INODE) {
> + inode_only = LOG_INODE_EXISTS;
> + mutex_lock_nested(&BTRFS_I(inode)->log_mutex, 1);
> + } else {
> + mutex_lock(&BTRFS_I(inode)->log_mutex);
> + }
>
> /*
> * a brute force approach to making sure we get the most uptodate
> @@ -4800,7 +4806,7 @@ static int btrfs_log_inode(struct btrfs_trans_handle *trans,
> * unpin it.
> */
> err = btrfs_log_inode(trans, root, other_inode,
> - LOG_INODE_EXISTS,
> + LOG_OTHER_INODE,
> 0, LLONG_MAX, ctx);
> iput(other_inode);
> if (err)
> --
> 2.5.5
>
--
Filipe David Manana,
"People will forget what you said,
people will forget what you did,
but people will never forget how you made them feel."
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