xfs: go straight to real allocations for direct I/O COW writes

When we allocate COW fork blocks for direct I/O writes we currently first
create a delayed allocation, and then convert it to a real allocation
once we've got the delayed one.

As there is no good reason for that this patch instead makes use call
xfs_bmapi_write from the COW allocation path.  The only interesting bits
are a few tweaks the low-level allocator to allow for this, most notably
the need to remove the call to xfs_bmap_extsize_align for the cowextsize
in xfs_bmap_btalloc - for the existing convert case it's a no-op, but
for the direct allocation case it would blow up our block reservation
way beyond what we reserved for the transaction.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index dcffbb0..1cee514 100644 (file)
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -2895,13 +2895,14 @@ xfs_bmap_add_extent_hole_real(
        ASSERT(!isnullstartblock(new->br_startblock));
        ASSERT(!bma->cur ||
               !(bma->cur->bc_private.b.flags & XFS_BTCUR_BPRV_WASDEL));
-       ASSERT(whichfork != XFS_COW_FORK);
 
        XFS_STATS_INC(mp, xs_add_exlist);
 
        state = 0;
        if (whichfork == XFS_ATTR_FORK)
                state |= BMAP_ATTRFORK;
+       if (whichfork == XFS_COW_FORK)
+               state |= BMAP_COWFORK;
 
        /*
         * Check and set flags if this segment has a left neighbor.

diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index 219bc96..9bba084 100644 (file)
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -389,62 +389,100 @@ __xfs_reflink_allocate_cow(
        xfs_fileoff_t           end_fsb)
 {
        struct xfs_mount        *mp = ip->i_mount;
-       struct xfs_bmbt_irec    imap;
+       struct xfs_bmbt_irec    imap, got;
        struct xfs_defer_ops    dfops;
        struct xfs_trans        *tp;
        xfs_fsblock_t           first_block;
-       int                     nimaps = 1, error;
-       bool                    shared;
+       int                     nimaps, error, lockmode;
+       bool                    shared, trimmed;
+       xfs_filblks_t           resaligned;
+       xfs_extlen_t            resblks;
+       xfs_extnum_t            idx;
 
-       xfs_defer_init(&dfops, &first_block);
+       resaligned = xfs_aligned_fsb_count(*offset_fsb, end_fsb - *offset_fsb,
+                       xfs_get_cowextsz_hint(ip));
+       resblks = XFS_DIOSTRAT_SPACE_RES(mp, resaligned);
 
-       error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, 0, 0,
-                       XFS_TRANS_RESERVE, &tp);
+       error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, 0, 0, &tp);
        if (error)
                return error;
 
-       xfs_ilock(ip, XFS_ILOCK_EXCL);
+       lockmode = XFS_ILOCK_EXCL;
+       xfs_ilock(ip, lockmode);
 
-       /* Read extent from the source file. */
-       nimaps = 1;
-       error = xfs_bmapi_read(ip, *offset_fsb, end_fsb - *offset_fsb,
-                       &imap, &nimaps, 0);
-       if (error)
-               goto out_unlock;
-       ASSERT(nimaps == 1);
+       /*
+        * 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, &idx, &got) &&
+           got.br_startoff <= *offset_fsb) {
+               /* If we have a real allocation in the COW fork we're done. */
+               if (!isnullstartblock(got.br_startblock)) {
+                       xfs_trim_extent(&got, *offset_fsb,
+                                       end_fsb - *offset_fsb);
+                       *offset_fsb = got.br_startoff + got.br_blockcount;
+                       goto out_trans_cancel;
+               }
+       } else {
+               nimaps = 1;
+               error = xfs_bmapi_read(ip, *offset_fsb, end_fsb - *offset_fsb,
+                               &imap, &nimaps, 0);
+               if (error)
+                       goto out_trans_cancel;
+               ASSERT(nimaps == 1);
+
+               /* Trim the mapping to the nearest shared extent boundary. */
+               error = xfs_reflink_trim_around_shared(ip, &imap, &shared,
+                               &trimmed);
+               if (error)
+                       goto out_trans_cancel;
+
+               if (!shared) {
+                       *offset_fsb = imap.br_startoff + imap.br_blockcount;
+                       goto out_trans_cancel;
+               }
 
-       /* Make sure there's a CoW reservation for it. */
-       error = xfs_reflink_reserve_cow(ip, &imap, &shared);
+               *offset_fsb = imap.br_startoff;
+               end_fsb = imap.br_startoff + imap.br_blockcount;
+       }
+
+       error = xfs_trans_reserve_quota_nblks(tp, ip, resblks, 0,
+                       XFS_QMOPT_RES_REGBLKS);
        if (error)
                goto out_trans_cancel;
 
-       if (!shared) {
-               *offset_fsb = imap.br_startoff + imap.br_blockcount;
-               goto out_trans_cancel;
-       }
+       xfs_trans_ijoin(tp, ip, 0);
+
+       xfs_defer_init(&dfops, &first_block);
+       nimaps = 1;
 
        /* Allocate the entire reservation as unwritten blocks. */
-       xfs_trans_ijoin(tp, ip, 0);
-       error = xfs_bmapi_write(tp, ip, imap.br_startoff, imap.br_blockcount,
+       error = xfs_bmapi_write(tp, ip, *offset_fsb, end_fsb - *offset_fsb,
                        XFS_BMAPI_COWFORK | XFS_BMAPI_PREALLOC, &first_block,
-                       XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK),
-                       &imap, &nimaps, &dfops);
+                       resblks, &imap, &nimaps, &dfops);
        if (error)
-               goto out_trans_cancel;
+               goto out_bmap_cancel;
 
        /* Finish up. */
        error = xfs_defer_finish(&tp, &dfops, NULL);
        if (error)
-               goto out_trans_cancel;
+               goto out_bmap_cancel;
 
        error = xfs_trans_commit(tp);
+       if (error)
+               goto out_unlock;
 
        *offset_fsb = imap.br_startoff + imap.br_blockcount;
+
 out_unlock:
-       xfs_iunlock(ip, XFS_ILOCK_EXCL);
+       xfs_iunlock(ip, lockmode);
        return error;
-out_trans_cancel:
+
+out_bmap_cancel:
        xfs_defer_cancel(&dfops);
+       xfs_trans_unreserve_quota_nblks(tp, ip, (long)resblks, 0,
+                       XFS_QMOPT_RES_REGBLKS);
+out_trans_cancel:
        xfs_trans_cancel(tp);
        goto out_unlock;
 }