1 files changed, 77 insertions, 50 deletions

diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index 38f405415b88..d60d0eeed7b9 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -352,6 +352,47 @@ xfs_reflink_convert_cow(
         return error;
 }
 
+/*
+ * Find the extent that maps the given range in the COW fork. Even if the extent
+ * is not shared we might have a preallocation for it in the COW fork. If so we
+ * use it that rather than trigger a new allocation.
+ */
+static int
+xfs_find_trim_cow_extent(
+        struct xfs_inode        *ip,
+        struct xfs_bmbt_irec    *imap,
+        bool                    *shared,
+        bool                    *found)
+{
+        xfs_fileoff_t           offset_fsb = imap->br_startoff;
+        xfs_filblks_t           count_fsb = imap->br_blockcount;
+        struct xfs_iext_cursor  icur;
+        struct xfs_bmbt_irec    got;
+        bool                    trimmed;
+
+        *found = false;
+
+        /*
+         * If we don't find an overlapping extent, trim the range we need to
+         * allocate to fit the hole we found.
+         */
+        if (!xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &icur, &got) ||
+            got.br_startoff > offset_fsb)
+                return xfs_reflink_trim_around_shared(ip, imap, shared, &trimmed);
+
+        *shared = true;
+        if (isnullstartblock(got.br_startblock)) {
+                xfs_trim_extent(imap, got.br_startoff, got.br_blockcount);
+                return 0;
+        }
+
+        /* real extent found - no need to allocate */
+        xfs_trim_extent(&got, offset_fsb, count_fsb);
+        *imap = got;
+        *found = true;
+        return 0;
+}
+
 /* Allocate all CoW reservations covering a range of blocks in a file. */
 int
 xfs_reflink_allocate_cow(
@@ -363,78 +404,64 @@ xfs_reflink_allocate_cow(
         struct xfs_mount        *mp = ip->i_mount;
         xfs_fileoff_t           offset_fsb = imap->br_startoff;
         xfs_filblks_t           count_fsb = imap->br_blockcount;
-        struct xfs_bmbt_irec    got;
-        struct xfs_trans        *tp = NULL;
+        struct xfs_trans        *tp;
         int                     nimaps, error = 0;
-        bool                    trimmed;
+        bool                    found;
         xfs_filblks_t           resaligned;
         xfs_extlen_t            resblks = 0;
-        struct xfs_iext_cursor  icur;
 
-retry:
-        ASSERT(xfs_is_reflink_inode(ip));
         ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
+        ASSERT(xfs_is_reflink_inode(ip));
 
-        /*
-         * Even if the extent is not shared we might have a preallocation for
-         * it in the COW fork.  If so use it.
-         */
-        if (xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &icur, &got) &&
-            got.br_startoff <= offset_fsb) {
-                *shared = true;
-
-                /* If we have a real allocation in the COW fork we're done. */
-                if (!isnullstartblock(got.br_startblock)) {
-                        xfs_trim_extent(&got, offset_fsb, count_fsb);
-                        *imap = got;
-                        goto convert;
-                }
+        error = xfs_find_trim_cow_extent(ip, imap, shared, &found);
+        if (error || !*shared)
+                return error;
+        if (found)
+                goto convert;
 
-                xfs_trim_extent(imap, got.br_startoff, got.br_blockcount);
-        } else {
-                error = xfs_reflink_trim_around_shared(ip, imap, shared, &trimmed);
-                if (error || !*shared)
-                        goto out;
-        }
+        resaligned = xfs_aligned_fsb_count(imap->br_startoff,
+                imap->br_blockcount, xfs_get_cowextsz_hint(ip));
+        resblks = XFS_DIOSTRAT_SPACE_RES(mp, resaligned);
 
-        if (!tp) {
-                resaligned = xfs_aligned_fsb_count(imap->br_startoff,
-                        imap->br_blockcount, xfs_get_cowextsz_hint(ip));
-                resblks = XFS_DIOSTRAT_SPACE_RES(mp, resaligned);
+        xfs_iunlock(ip, *lockmode);
+        error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, 0, 0, &tp);
+        *lockmode = XFS_ILOCK_EXCL;
+        xfs_ilock(ip, *lockmode);
 
-                xfs_iunlock(ip, *lockmode);
-                error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, 0, 0, &tp);
-                *lockmode = XFS_ILOCK_EXCL;
-                xfs_ilock(ip, *lockmode);
+        if (error)
+                return error;
 
-                if (error)
-                        return error;
+        error = xfs_qm_dqattach_locked(ip, false);
+        if (error)
+                goto out_trans_cancel;
 
-                error = xfs_qm_dqattach_locked(ip, false);
-                if (error)
-                        goto out;
-                goto retry;
+        /*
+         * Check for an overlapping extent again now that we dropped the ilock.
+         */
+        error = xfs_find_trim_cow_extent(ip, imap, shared, &found);
+        if (error || !*shared)
+                goto out_trans_cancel;
+        if (found) {
+                xfs_trans_cancel(tp);
+                goto convert;
         }
 
         error = xfs_trans_reserve_quota_nblks(tp, ip, resblks, 0,
                         XFS_QMOPT_RES_REGBLKS);
         if (error)
-                goto out;
+                goto out_trans_cancel;
 
         xfs_trans_ijoin(tp, ip, 0);
 
-        nimaps = 1;
-
         /* Allocate the entire reservation as unwritten blocks. */
+        nimaps = 1;
         error = xfs_bmapi_write(tp, ip, imap->br_startoff, imap->br_blockcount,
                         XFS_BMAPI_COWFORK | XFS_BMAPI_PREALLOC,
                         resblks, imap, &nimaps);
         if (error)
-                goto out_trans_cancel;
+                goto out_unreserve;
 
         xfs_inode_set_cowblocks_tag(ip);
-
-        /* Finish up. */
         error = xfs_trans_commit(tp);
         if (error)
                 return error;
@@ -447,12 +474,12 @@ retry:
                 return -ENOSPC;
 convert:
         return xfs_reflink_convert_cow_extent(ip, imap, offset_fsb, count_fsb);
-out_trans_cancel:
+
+out_unreserve:
         xfs_trans_unreserve_quota_nblks(tp, ip, (long)resblks, 0,
                         XFS_QMOPT_RES_REGBLKS);
-out:
-        if (tp)
-                xfs_trans_cancel(tp);
+out_trans_cancel:
+        xfs_trans_cancel(tp);
         return error;
 }