xfs: only lock the rt bitmap inode once per allocation

Currently both xfs_rtpick_extent and xfs_rtallocate_extent call
xfs_trans_iget to grab and lock the rt bitmap inode, which results in a
deadlock since the removal of the lock recursion counters in commit

	"xfs: simplify inode to transaction joining"

Fix this by acquiring and locking the inode in xfs_bmap_rtalloc before
calling into xfs_rtpick_extent and xfs_rtallocate_extent.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/fs/xfs/xfs_bmap.c b/fs/xfs/xfs_bmap.c
index dc3afd7739ff..2f89af25996f 100644
--- a/fs/xfs/xfs_bmap.c
+++ b/fs/xfs/xfs_bmap.c
@@ -2333,6 +2333,7 @@ xfs_bmap_rtalloc(
         xfs_extlen_t    prod = 0;       /* product factor for allocators */
         xfs_extlen_t    ralen = 0;      /* realtime allocation length */
         xfs_extlen_t    align;          /* minimum allocation alignment */
+        xfs_inode_t     *ip;            /* bitmap incore inode */
         xfs_rtblock_t   rtb;
 
         mp = ap->ip->i_mount;
@@ -2365,6 +2366,16 @@ xfs_bmap_rtalloc(
          */
         if (ralen * mp->m_sb.sb_rextsize >= MAXEXTLEN)
                 ralen = MAXEXTLEN / mp->m_sb.sb_rextsize;
+
+        /*
+         * Lock out other modifications to the RT bitmap inode.
+         */
+        error = xfs_trans_iget(mp, ap->tp, mp->m_sb.sb_rbmino, 0,
+                               XFS_ILOCK_EXCL, &ip);
+        if (error)
+                return error;
+        ASSERT(ip == mp->m_rbmip);
+
         /*
          * If it's an allocation to an empty file at offset 0,
          * pick an extent that will space things out in the rt area.