| Message ID | 20210111225053.GE1164246@magnolia (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | [v3] xfs: fix an ABBA deadlock in xfs_rename | expand |
On Mon, Jan 11, 2021 at 02:50:53PM -0800, Darrick J. Wong wrote: > From: Darrick J. Wong <djwong@kernel.org> > Subject: [PATCH] xfs: fix an ABBA deadlock in xfs_rename > > When overlayfs is running on top of xfs and the user unlinks a file in > the overlay, overlayfs will create a whiteout inode and ask xfs to > "rename" the whiteout file atop the one being unlinked. If the file > being unlinked loses its one nlink, we then have to put the inode on the > unlinked list. > > This requires us to grab the AGI buffer of the whiteout inode to take it > off the unlinked list (which is where whiteouts are created) and to grab > the AGI buffer of the file being deleted. If the whiteout was created > in a higher numbered AG than the file being deleted, we'll lock the AGIs > in the wrong order and deadlock. > > Therefore, grab all the AGI locks we think we'll need ahead of time, and > in order of increasing AG number per the locking rules. > > Reported-by: wenli xie <wlxie7296@gmail.com> > Fixes: 93597ae8dac0 ("xfs: Fix deadlock between AGI and AGF when target_ip exists in xfs_rename()") > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> > --- > v2: Make it more obvious that we're grabbing all the AGI locks ahead of > the AGFs, and hide functions that we don't need to export anymore. > v3: condense the predicate code even further > --- Looks good, thanks for the tweaks: Reviewed-by: Brian Foster <bfoster@redhat.com> > fs/xfs/libxfs/xfs_dir2.h | 2 -- > fs/xfs/libxfs/xfs_dir2_sf.c | 2 +- > fs/xfs/xfs_inode.c | 42 +++++++++++++++++++++++++----------------- > 3 files changed, 26 insertions(+), 20 deletions(-) > > diff --git a/fs/xfs/libxfs/xfs_dir2.h b/fs/xfs/libxfs/xfs_dir2.h > index e55378640b05..d03e6098ded9 100644 > --- a/fs/xfs/libxfs/xfs_dir2.h > +++ b/fs/xfs/libxfs/xfs_dir2.h > @@ -47,8 +47,6 @@ 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_dir2_sf_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/libxfs/xfs_dir2_sf.c b/fs/xfs/libxfs/xfs_dir2_sf.c > index 2463b5d73447..8c4f76bba88b 100644 > --- a/fs/xfs/libxfs/xfs_dir2_sf.c > +++ b/fs/xfs/libxfs/xfs_dir2_sf.c > @@ -1018,7 +1018,7 @@ xfs_dir2_sf_removename( > /* > * Check whether the sf dir replace operation need more blocks. > */ > -bool > +static bool > xfs_dir2_sf_replace_needblock( > struct xfs_inode *dp, > xfs_ino_t inum) > diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c > index b7352bc4c815..e5dc41b10ebb 100644 > --- a/fs/xfs/xfs_inode.c > +++ b/fs/xfs/xfs_inode.c > @@ -3017,7 +3017,7 @@ xfs_rename( > struct xfs_trans *tp; > struct xfs_inode *wip = NULL; /* whiteout inode */ > struct xfs_inode *inodes[__XFS_SORT_INODES]; > - struct xfs_buf *agibp; > + int i; > 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); > @@ -3130,6 +3130,30 @@ xfs_rename( > } > } > > + /* > + * Lock the AGI buffers we need to handle bumping the nlink of the > + * whiteout inode off the unlinked list and to handle dropping the > + * nlink of the target inode. Per locking order rules, do this in > + * increasing AG order and before directory block allocation tries to > + * grab AGFs because we grab AGIs before AGFs. > + * > + * The (vfs) caller must ensure that if src is a directory then > + * target_ip is either null or an empty directory. > + */ > + for (i = 0; i < num_inodes && inodes[i] != NULL; i++) { > + if (inodes[i] == wip || > + (inodes[i] == target_ip && > + (VFS_I(target_ip)->i_nlink == 1 || src_is_directory))) { > + struct xfs_buf *bp; > + xfs_agnumber_t agno; > + > + agno = XFS_INO_TO_AGNO(mp, inodes[i]->i_ino); > + error = xfs_read_agi(mp, tp, agno, &bp); > + if (error) > + goto out_trans_cancel; > + } > + } > + > /* > * Directory entry creation below may acquire the AGF. Remove > * the whiteout from the unlinked list first to preserve correct > @@ -3182,22 +3206,6 @@ xfs_rename( > * In case there is already an entry with the same > * name at the destination directory, remove it first. > */ > - > - /* > - * Check whether the replace operation will need to allocate > - * blocks. This happens when the shortform directory lacks > - * space and we have to convert it to a block format directory. > - * When more blocks are necessary, we must lock the AGI first > - * to preserve locking order (AGI -> AGF). > - */ > - if (xfs_dir2_sf_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) >
diff --git a/fs/xfs/libxfs/xfs_dir2.h b/fs/xfs/libxfs/xfs_dir2.h index e55378640b05..d03e6098ded9 100644 --- a/fs/xfs/libxfs/xfs_dir2.h +++ b/fs/xfs/libxfs/xfs_dir2.h @@ -47,8 +47,6 @@ 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_dir2_sf_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/libxfs/xfs_dir2_sf.c b/fs/xfs/libxfs/xfs_dir2_sf.c index 2463b5d73447..8c4f76bba88b 100644 --- a/fs/xfs/libxfs/xfs_dir2_sf.c +++ b/fs/xfs/libxfs/xfs_dir2_sf.c @@ -1018,7 +1018,7 @@ xfs_dir2_sf_removename( /* * Check whether the sf dir replace operation need more blocks. */ -bool +static bool xfs_dir2_sf_replace_needblock( struct xfs_inode *dp, xfs_ino_t inum) diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c index b7352bc4c815..e5dc41b10ebb 100644 --- a/fs/xfs/xfs_inode.c +++ b/fs/xfs/xfs_inode.c @@ -3017,7 +3017,7 @@ xfs_rename( struct xfs_trans *tp; struct xfs_inode *wip = NULL; /* whiteout inode */ struct xfs_inode *inodes[__XFS_SORT_INODES]; - struct xfs_buf *agibp; + int i; 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); @@ -3130,6 +3130,30 @@ xfs_rename( } } + /* + * Lock the AGI buffers we need to handle bumping the nlink of the + * whiteout inode off the unlinked list and to handle dropping the + * nlink of the target inode. Per locking order rules, do this in + * increasing AG order and before directory block allocation tries to + * grab AGFs because we grab AGIs before AGFs. + * + * The (vfs) caller must ensure that if src is a directory then + * target_ip is either null or an empty directory. + */ + for (i = 0; i < num_inodes && inodes[i] != NULL; i++) { + if (inodes[i] == wip || + (inodes[i] == target_ip && + (VFS_I(target_ip)->i_nlink == 1 || src_is_directory))) { + struct xfs_buf *bp; + xfs_agnumber_t agno; + + agno = XFS_INO_TO_AGNO(mp, inodes[i]->i_ino); + error = xfs_read_agi(mp, tp, agno, &bp); + if (error) + goto out_trans_cancel; + } + } + /* * Directory entry creation below may acquire the AGF. Remove * the whiteout from the unlinked list first to preserve correct @@ -3182,22 +3206,6 @@ xfs_rename( * In case there is already an entry with the same * name at the destination directory, remove it first. */ - - /* - * Check whether the replace operation will need to allocate - * blocks. This happens when the shortform directory lacks - * space and we have to convert it to a block format directory. - * When more blocks are necessary, we must lock the AGI first - * to preserve locking order (AGI -> AGF). - */ - if (xfs_dir2_sf_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)