xfs: add scan owner field to xfs_eofblocks

From: Brian Foster <bfoster@redhat.com>

The scan owner field represents an optional inode number that is
responsible for the current scan. The purpose is to identify that an
inode is under iolock and as such, the iolock shouldn't be attempted
when trimming eofblocks. This is an internal only field.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

2 files changed, 14 insertions, 1 deletions

diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
index 08ba4c6e1359..6e522ff5a006 100644
--- a/fs/xfs/xfs_icache.c
+++ b/fs/xfs/xfs_icache.c
@@ -1211,6 +1211,9 @@ xfs_inode_free_eofblocks(
 {
         int ret;
         struct xfs_eofblocks *eofb = args;
+        bool need_iolock = true;
+
+        ASSERT(!eofb || (eofb && eofb->eof_scan_owner != 0));
 
         if (!xfs_can_free_eofblocks(ip, false)) {
                 /* inode could be preallocated or append-only */
@@ -1235,9 +1238,17 @@ xfs_inode_free_eofblocks(
                 if (eofb->eof_flags & XFS_EOF_FLAGS_MINFILESIZE &&
                     XFS_ISIZE(ip) < eofb->eof_min_file_size)
                         return 0;
+
+                /*
+                 * A scan owner implies we already hold the iolock. Skip it in
+                 * xfs_free_eofblocks() to avoid deadlock. This also eliminates
+                 * the possibility of EAGAIN being returned.
+                 */
+                if (eofb->eof_scan_owner == ip->i_ino)
+                        need_iolock = false;
         }
 
-        ret = xfs_free_eofblocks(ip->i_mount, ip, true);
+        ret = xfs_free_eofblocks(ip->i_mount, ip, need_iolock);
 
         /* don't revisit the inode if we're not waiting */
         if (ret == -EAGAIN && !(flags & SYNC_WAIT))
diff --git a/fs/xfs/xfs_icache.h b/fs/xfs/xfs_icache.h
index 6250430d609c..98687af6a99d 100644
--- a/fs/xfs/xfs_icache.h
+++ b/fs/xfs/xfs_icache.h
@@ -27,6 +27,7 @@ struct xfs_eofblocks {
         kgid_t          eof_gid;
         prid_t          eof_prid;
         __u64           eof_min_file_size;
+        xfs_ino_t       eof_scan_owner;
 };
 
 #define SYNC_WAIT               0x0001  /* wait for i/o to complete */
@@ -84,6 +85,7 @@ xfs_fs_eofblocks_from_user(
         dst->eof_flags = src->eof_flags;
         dst->eof_prid = src->eof_prid;
         dst->eof_min_file_size = src->eof_min_file_size;
+        dst->eof_scan_owner = NULLFSINO;
 
         dst->eof_uid = INVALID_UID;
         if (src->eof_flags & XFS_EOF_FLAGS_UID) {