On Wed, Oct 30, 2019 at 05:49:34PM +0800, kaixuxia wrote:
> When target_ip exists in xfs_rename(), the xfs_dir_replace() call may
> need to hold the AGF lock to allocate more blocks, and then invoking
> the xfs_droplink() call to hold AGI lock to drop target_ip onto the
> unlinked list, so we get the lock order AGF->AGI. This would break the
> ordering constraint on AGI and AGF locking - inode allocation locks
> the AGI, then can allocate a new extent for new inodes, locking the
> AGF after the AGI.
>
> In this patch we check whether the replace operation need more
> blocks firstly. If so, acquire the agi lock firstly to preserve
> locking order(AGI/AGF). Actually, the locking order problem only
> occurs when we are locking the AGI/AGF of the same AG. For multiple
> AGs the AGI lock will be released after the transaction committed.
>
> Signed-off-by: kaixuxia <kaixuxia@xxxxxxxxxxx>
> ---
> fs/xfs/libxfs/xfs_dir2.c | 30 ++++++++++++++++++++++++++++++
> fs/xfs/libxfs/xfs_dir2.h | 2 ++
> fs/xfs/xfs_inode.c | 14 ++++++++++++++
> 3 files changed, 46 insertions(+)
>
> diff --git a/fs/xfs/libxfs/xfs_dir2.c b/fs/xfs/libxfs/xfs_dir2.c
> index 867c5de..9d9ae16 100644
> --- a/fs/xfs/libxfs/xfs_dir2.c
> +++ b/fs/xfs/libxfs/xfs_dir2.c
> @@ -463,6 +463,36 @@
> }
>
> /*
> + * Check whether the replace operation need more blocks. Ignore
> + * the parameters check since the real replace() call below will
> + * do that.
> + */
> +bool
> +xfs_dir_replace_needblock(
> + struct xfs_inode *dp,
> + xfs_ino_t inum)
> +{
> + int newsize;
> + xfs_dir2_sf_hdr_t *sfp;
> +
> + /*
> + * Only convert the shortform directory to block form maybe need
> + * more blocks.
> + */
> + if (dp->i_d.di_format != XFS_DINODE_FMT_LOCAL)
> + return false;
> +
> + sfp = (xfs_dir2_sf_hdr_t *)dp->i_df.if_u1.if_data;
> + newsize = dp->i_df.if_bytes + (sfp->count + 1) * XFS_INO64_DIFF;
> +
> + if (inum > XFS_DIR2_MAX_SHORT_INUM &&
> + sfp->i8count == 0 && newsize > XFS_IFORK_DSIZE(dp))
> + return true;
> + else
> + return false;
> +}
> +
It's slightly unfortunate we need to do these kind of double checks, but
it seems reasonable enough as an isolated fix. From a factoring
standpoint, it might be a little cleaner to move this down in
xfs_dir2_sf.c as an xfs_dir2_sf_replace_needblock() helper, actually use
it in the xfs_dir2_sf_replace() function where these checks are
currently open coded and then export it so we can call it in the higher
level function as well for the locking fix.
Brian
> +/*
> * Replace the inode number of a directory entry.
> */
> int
> diff --git a/fs/xfs/libxfs/xfs_dir2.h b/fs/xfs/libxfs/xfs_dir2.h
> index f542447..e436c14 100644
> --- a/fs/xfs/libxfs/xfs_dir2.h
> +++ b/fs/xfs/libxfs/xfs_dir2.h
> @@ -124,6 +124,8 @@ extern int xfs_dir_lookup(struct xfs_trans *tp, struct xfs_inode *dp,
> extern int xfs_dir_removename(struct xfs_trans *tp, struct xfs_inode *dp,
> struct xfs_name *name, xfs_ino_t ino,
> xfs_extlen_t tot);
> +extern bool xfs_dir_replace_needblock(struct xfs_inode *dp,
> + xfs_ino_t inum);
> extern int xfs_dir_replace(struct xfs_trans *tp, struct xfs_inode *dp,
> struct xfs_name *name, xfs_ino_t inum,
> xfs_extlen_t tot);
> diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
> index 18f4b26..c239070 100644
> --- a/fs/xfs/xfs_inode.c
> +++ b/fs/xfs/xfs_inode.c
> @@ -3196,6 +3196,7 @@ struct xfs_iunlink {
> struct xfs_trans *tp;
> struct xfs_inode *wip = NULL; /* whiteout inode */
> struct xfs_inode *inodes[__XFS_SORT_INODES];
> + struct xfs_buf *agibp;
> int num_inodes = __XFS_SORT_INODES;
> bool new_parent = (src_dp != target_dp);
> bool src_is_directory = S_ISDIR(VFS_I(src_ip)->i_mode);
> @@ -3361,6 +3362,19 @@ struct xfs_iunlink {
> * In case there is already an entry with the same
> * name at the destination directory, remove it first.
> */
> +
> + /*
> + * Check whether the replace operation need more blocks.
> + * If so, acquire the agi lock firstly to preserve locking
> + * order(AGI/AGF).
> + */
> + if (xfs_dir_replace_needblock(target_dp, src_ip->i_ino)) {
> + error = xfs_read_agi(mp, tp,
> + XFS_INO_TO_AGNO(mp, target_ip->i_ino), &agibp);
> + if (error)
> + goto out_trans_cancel;
> + }
> +
> error = xfs_dir_replace(tp, target_dp, target_name,
> src_ip->i_ino, spaceres);
> if (error)
> --
> 1.8.3.1
>
