xfs: make metabtree reservations global

Currently each metabtree inode has it's own space reservation to ensure
it can be expanded to the maximum size, mirroring what is done for the
AG-based btrees.  But unlike the AG-based btrees the metabtree inodes
aren't restricted to allocate from a single AG but can use free space
form the entire file system.  And unlike AG-based btrees where the
required reservation shrinks with the available free space due to this,
the metabtree reservations for the rtrmap and rtfreflink trees are not
bound in any way by the data device free space as they track RT extent
allocations.  This is not very efficient as it requires a large number
of blocks to be set aside that can't be used at all by other btrees.

Switch to a model that uses a global pool instead in preparation for
reducing the amount of reserved space, which now also removes the
overloading of the i_nblocks field for metabtree inodes, which would
create problems if metabtree inodes ever had a big enough xattr fork
to require xattr blocks outside the inode.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

1 files changed, 14 insertions, 14 deletions

diff --git a/fs/xfs/scrub/repair.c b/fs/xfs/scrub/repair.c
index 3b5288d3ef4e..c2705c3cba0d 100644
--- a/fs/xfs/scrub/repair.c
+++ b/fs/xfs/scrub/repair.c
@@ -1386,11 +1386,12 @@ int
 xrep_reset_metafile_resv(
 	struct xfs_scrub	*sc)
 {
-	struct xfs_inode	*ip = sc->ip;
+	struct xfs_mount	*mp = sc->mp;
 	int64_t			delta;
 	int			error;
 
-	delta = ip->i_nblocks + ip->i_delayed_blks - ip->i_meta_resv_asked;
+	delta = mp->m_metafile_resv_used + mp->m_metafile_resv_avail -
+		mp->m_metafile_resv_target;
 	if (delta == 0)
 		return 0;
 
@@ -1401,11 +1402,11 @@ xrep_reset_metafile_resv(
 	if (delta > 0) {
 		int64_t		give_back;
 
-		give_back = min_t(uint64_t, delta, ip->i_delayed_blks);
+		give_back = min_t(uint64_t, delta, mp->m_metafile_resv_avail);
 		if (give_back > 0) {
-			xfs_mod_delalloc(ip, 0, -give_back);
-			xfs_add_fdblocks(ip->i_mount, give_back);
-			ip->i_delayed_blks -= give_back;
+			xfs_mod_sb_delalloc(mp, -give_back);
+			xfs_add_fdblocks(mp, give_back);
+			mp->m_metafile_resv_avail -= give_back;
 		}
 
 		return 0;
@@ -1413,24 +1414,23 @@ xrep_reset_metafile_resv(
 
 	/*
 	 * Not enough reservation; try to take some blocks from the filesystem
-	 * to the metadata inode.  @delta is negative here, so invert the sign.
+	 * to the metabtree reservation.
 	 */
-	delta = -delta;
-	error = xfs_dec_fdblocks(sc->mp, delta, true);
+	delta = -delta; /* delta is negative here, so invert the sign. */
+	error = xfs_dec_fdblocks(mp, delta, true);
 	while (error == -ENOSPC) {
 		delta--;
 		if (delta == 0) {
 			xfs_warn(sc->mp,
-"Insufficient free space to reset space reservation for inode 0x%llx after repair.",
-					ip->i_ino);
+"Insufficient free space to reset metabtree reservation after repair.");
 			return 0;
 		}
-		error = xfs_dec_fdblocks(sc->mp, delta, true);
+		error = xfs_dec_fdblocks(mp, delta, true);
 	}
 	if (error)
 		return error;
 
-	xfs_mod_delalloc(ip, 0, delta);
-	ip->i_delayed_blks += delta;
+	xfs_mod_sb_delalloc(mp, delta);
+	mp->m_metafile_resv_avail += delta;
 	return 0;
 }