[TRUSTY SRU][PATCH] xfs: xfs_dir2_block_to_sf temp buffer allocation fails

[Rafael David Tinoco]

Buglink: https://bugs.launchpad.net/bugs/1382333

If we are using a large directory block size, and memory becomes
fragmented, we can get memory allocation failures trying to
kmem_alloc(64k) for a temporary buffer. However, there is not need
for a directory buffer sized allocation, as the end result ends up
in the inode literal area. This is, at most, slightly less than 2k
of space, and hence we don't need an allocation larger than that
fora temporary buffer.

OriginalAuthor: Dave Chinner <dchinner at redhat.com>
Signed-off-by: Dave Chinner <dchinner at redhat.com>
Reviewed-by: Ben Myers <bpm at sgi.com>
Signed-off-by: Ben Myers <bpm at sgi.com>
(cherry-picked from commit b3f03bac8132207a20286d5602eda64500c19724 v3.14-rc1)
Signed-off-by: Rafael David Tinoco <rafael.tinoco at canonical.com>

---
 fs/xfs/xfs_dir2_sf.c | 58 ++++++++++++++++++++++++++++++----------------------
 1 file changed, 34 insertions(+), 24 deletions(-)

diff --git a/fs/xfs/xfs_dir2_sf.c b/fs/xfs/xfs_dir2_sf.c
index aafc6e4..3725fb1 100644
--- a/fs/xfs/xfs_dir2_sf.c
+++ b/fs/xfs/xfs_dir2_sf.c
@@ -170,6 +170,7 @@ xfs_dir2_block_to_sf(
 	char			*ptr;		/* current data pointer */
 	xfs_dir2_sf_entry_t	*sfep;		/* shortform entry */
 	xfs_dir2_sf_hdr_t	*sfp;		/* shortform directory header */
+	xfs_dir2_sf_hdr_t	*dst;		/* temporary data buffer */
 
 	trace_xfs_dir2_block_to_sf(args);
 
@@ -177,35 +178,20 @@ xfs_dir2_block_to_sf(
 	mp = dp->i_mount;
 
 	/*
-	 * Make a copy of the block data, so we can shrink the inode
-	 * and add local data.
+	 * allocate a temporary destination buffer the size of the inode
+	 * to format the data into. Once we have formatted the data, we
+	 * can free the block and copy the formatted data into the inode literal
+	 * area.
 	 */
-	hdr = kmem_alloc(mp->m_dirblksize, KM_SLEEP);
-	memcpy(hdr, bp->b_addr, mp->m_dirblksize);
-	logflags = XFS_ILOG_CORE;
-	if ((error = xfs_dir2_shrink_inode(args, mp->m_dirdatablk, bp))) {
-		ASSERT(error != ENOSPC);
-		goto out;
-	}
+	dst = kmem_alloc(mp->m_sb.sb_inodesize, KM_SLEEP);
+	hdr = bp->b_addr;
 
 	/*
-	 * The buffer is now unconditionally gone, whether
-	 * xfs_dir2_shrink_inode worked or not.
-	 *
-	 * Convert the inode to local format.
-	 */
-	dp->i_df.if_flags &= ~XFS_IFEXTENTS;
-	dp->i_df.if_flags |= XFS_IFINLINE;
-	dp->i_d.di_format = XFS_DINODE_FMT_LOCAL;
-	ASSERT(dp->i_df.if_bytes == 0);
-	xfs_idata_realloc(dp, size, XFS_DATA_FORK);
-	logflags |= XFS_ILOG_DDATA;
-	/*
 	 * Copy the header into the newly allocate local space.
 	 */
-	sfp = (xfs_dir2_sf_hdr_t *)dp->i_df.if_u1.if_data;
+	sfp = (xfs_dir2_sf_hdr_t *)dst;
 	memcpy(sfp, sfhp, xfs_dir2_sf_hdr_size(sfhp->i8count));
-	dp->i_d.di_size = size;
+
 	/*
 	 * Set up to loop over the block's entries.
 	 */
@@ -258,10 +244,34 @@ xfs_dir2_block_to_sf(
 		ptr += dp->d_ops->data_entsize(dep->namelen);
 	}
 	ASSERT((char *)sfep - (char *)sfp == size);
+
+	/* now we are done with the block, we can shrink the inode */
+	logflags = XFS_ILOG_CORE;
+	error = xfs_dir2_shrink_inode(args, mp->m_dirdatablk, bp);
+	if (error) {
+		ASSERT(error != ENOSPC);
+		goto out;
+	}
+
+	/*
+	 * The buffer is now unconditionally gone, whether
+	 * xfs_dir2_shrink_inode worked or not.
+	 *
+	 * Convert the inode to local format and copy the data in.
+	 */
+	dp->i_df.if_flags &= ~XFS_IFEXTENTS;
+	dp->i_df.if_flags |= XFS_IFINLINE;
+	dp->i_d.di_format = XFS_DINODE_FMT_LOCAL;
+	ASSERT(dp->i_df.if_bytes == 0);
+	xfs_idata_realloc(dp, size, XFS_DATA_FORK);
+
+	logflags |= XFS_ILOG_DDATA;
+	memcpy(dp->i_df.if_u1.if_data, dst, size);
+	dp->i_d.di_size = size;
 	xfs_dir2_sf_check(args);
 out:
 	xfs_trans_log_inode(args->trans, dp, logflags);
-	kmem_free(hdr);
+	kmem_free(dst);
 	return error;
 }
 
-- 
2.1.1