On Tue, Nov 12, 2019 at 08:34:14AM -0800, Darrick J. Wong wrote:
> On Tue, Nov 12, 2019 at 07:13:30PM +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>
> > ---
> > Changes in v4:
> > -Remove the typedef usages.
> > -Invoke xfs_dir2_sf_replace_needblock() in
> > xfs_dir2_sf_replace() directly.
> >
> > fs/xfs/libxfs/xfs_dir2.h | 2 ++
> > fs/xfs/libxfs/xfs_dir2_sf.c | 28 +++++++++++++++++++++++-----
> > fs/xfs/xfs_inode.c | 15 +++++++++++++++
> > 3 files changed, 40 insertions(+), 5 deletions(-)
> >
> > diff --git a/fs/xfs/libxfs/xfs_dir2.h b/fs/xfs/libxfs/xfs_dir2.h
> > index f542447..01b1722 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_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 85f14fc..0e112e1 100644
> > --- a/fs/xfs/libxfs/xfs_dir2_sf.c
> > +++ b/fs/xfs/libxfs/xfs_dir2_sf.c
> > @@ -945,6 +945,27 @@ static int xfs_dir2_sf_addname_pick(xfs_da_args_t *args, int objchange,
> > }
> >
> > /*
> > + * Check whether the sf dir replace operation need more blocks.
> > + */
> > +bool
> > +xfs_dir2_sf_replace_needblock(
> > + struct xfs_inode *dp,
> > + xfs_ino_t inum)
> > +{
> > + int newsize;
> > + struct xfs_dir2_sf_hdr *sfp;
> > +
> > + if (dp->i_d.di_format != XFS_DINODE_FMT_LOCAL)
> > + return false;
> > +
> > + sfp = (struct xfs_dir2_sf_hdr *)dp->i_df.if_u1.if_data;
> > + newsize = dp->i_df.if_bytes + (sfp->count + 1) * XFS_INO64_DIFF;
> > +
> > + return inum > XFS_DIR2_MAX_SHORT_INUM &&
> > + sfp->i8count == 0 && newsize > XFS_IFORK_DSIZE(dp);
> > +}
> > +
> > +/*
> > * Replace the inode number of an entry in a shortform directory.
> > */
> > int /* error */
> > @@ -980,17 +1001,14 @@ static int xfs_dir2_sf_addname_pick(xfs_da_args_t *args, int objchange,
> > */
> > if (args->inumber > XFS_DIR2_MAX_SHORT_INUM && sfp->i8count == 0) {
> > int error; /* error return value */
> > - int newsize; /* new inode size */
> >
> > - newsize = dp->i_df.if_bytes + (sfp->count + 1) * XFS_INO64_DIFF;
> > /*
> > * Won't fit as shortform, convert to block then do replace.
> > */
> > - if (newsize > XFS_IFORK_DSIZE(dp)) {
> > + if (xfs_dir2_sf_replace_needblock(dp, args->inumber)) {
> > error = xfs_dir2_sf_to_block(args);
> > - if (error) {
> > + if (error)
> > return error;
> > - }
> > return xfs_dir2_block_replace(args);
> > }
> > /*
> > diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
> > index 18f4b26..5dc3796 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 +3362,20 @@ 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). Only convert the shortform directory to
> > + * block form maybe need more blocks.
>
> The comment still seems a little clunky. How about:
>
> "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);
>
> The second line needs a double indent.
>
> I can fix both of these on commit if Brian doesn't have any further
> suggestions.
>
> Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
>
I was hoping for a little more cleanup of the existing
xfs_dir2_sf_replace() logic, but that can always come later. This looks
correct to me and we might as well get this bug fixed. With Darrick's
adjustments:
Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>
> --D
>
> > + 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
> >
>
