[XFS] Sleeping with the ilock waiting for I/O completion is Bad.

Recent fixes to the filesystem freezing code introduced a vn_iowait call
in the middle of the sync code. Unfortunately, at the point where this
call was added we are holding the ilock. The ilock is needed by I/O
completion for unwritten extent conversion and now updating the file size.
Hence I/o cannot complete if we hold the ilock while waiting for I/O
completion.

Fix up the bug and clean the code up around it.

SGI-PV: 963674
SGI-Modid: xfs-linux-melb:xfs-kern:28566a

Signed-off-by: David Chinner <dgc@sgi.com>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Tim Shimmin <tes@sgi.com>

diff --git a/fs/xfs/xfs_vfsops.c b/fs/xfs/xfs_vfsops.c
index 65c561201cb879da8a83d1df3c40fe2af7927d96..92c1425d06cec2e537e00c8ec9797e41429d3bc3 100644 (file)
--- a/fs/xfs/xfs_vfsops.c
+++ b/fs/xfs/xfs_vfsops.c
@@ -1128,58 +1128,41 @@ xfs_sync_inodes(
                 * in the inode list.
                 */
 
-               if ((flags & SYNC_CLOSE)  && (vp != NULL)) {
-                       /*
-                        * This is the shutdown case.  We just need to
-                        * flush and invalidate all the pages associated
-                        * with the inode.  Drop the inode lock since
-                        * we can't hold it across calls to the buffer
-                        * cache.
-                        *
-                        * We don't set the VREMAPPING bit in the vnode
-                        * here, because we don't hold the vnode lock
-                        * exclusively.  It doesn't really matter, though,
-                        * because we only come here when we're shutting
-                        * down anyway.
-                        */
-                       xfs_iunlock(ip, XFS_ILOCK_SHARED);
-
-                       if (XFS_FORCED_SHUTDOWN(mp)) {
-                               bhv_vop_toss_pages(vp, 0, -1, FI_REMAPF);
-                       } else {
-                               error = bhv_vop_flushinval_pages(vp, 0, -1, FI_REMAPF);
+               /*
+                * If we have to flush data or wait for I/O completion
+                * we need to drop the ilock that we currently hold.
+                * If we need to drop the lock, insert a marker if we
+                * have not already done so.
+                */
+               if ((flags & (SYNC_CLOSE|SYNC_IOWAIT)) ||
+                   ((flags & SYNC_DELWRI) && VN_DIRTY(vp))) {
+                       if (mount_locked) {
+                               IPOINTER_INSERT(ip, mp);
                        }
+                       xfs_iunlock(ip, XFS_ILOCK_SHARED);
 
-                       xfs_ilock(ip, XFS_ILOCK_SHARED);
-
-               } else if ((flags & SYNC_DELWRI) && (vp != NULL)) {
-                       if (VN_DIRTY(vp)) {
-                               /* We need to have dropped the lock here,
-                                * so insert a marker if we have not already
-                                * done so.
-                                */
-                               if (mount_locked) {
-                                       IPOINTER_INSERT(ip, mp);
-                               }
-
-                               /*
-                                * Drop the inode lock since we can't hold it
-                                * across calls to the buffer cache.
-                                */
-                               xfs_iunlock(ip, XFS_ILOCK_SHARED);
+                       if (flags & SYNC_CLOSE) {
+                               /* Shutdown case. Flush and invalidate. */
+                               if (XFS_FORCED_SHUTDOWN(mp))
+                                       bhv_vop_toss_pages(vp, 0, -1, FI_REMAPF);
+                               else
+                                       error = bhv_vop_flushinval_pages(vp, 0,
+                                                               -1, FI_REMAPF);
+                       } else if ((flags & SYNC_DELWRI) && VN_DIRTY(vp)) {
                                error = bhv_vop_flush_pages(vp, (xfs_off_t)0,
                                                        -1, fflag, FI_NONE);
-                               xfs_ilock(ip, XFS_ILOCK_SHARED);
                        }
 
+                       /*
+                        * When freezing, we need to wait ensure all I/O (including direct
+                        * I/O) is complete to ensure no further data modification can take
+                        * place after this point
+                        */
+                       if (flags & SYNC_IOWAIT)
+                               vn_iowait(vp);
+
+                       xfs_ilock(ip, XFS_ILOCK_SHARED);
                }
-               /*
-                * When freezing, we need to wait ensure all I/O (including direct
-                * I/O) is complete to ensure no further data modification can take
-                * place after this point
-                */
-               if (flags & SYNC_IOWAIT)
-                       vn_iowait(vp);
 
                if (flags & SYNC_BDFLUSH) {
                        if ((flags & SYNC_ATTR) &&