xfs: rework splitting of indirect block reservations

Move the check if we have enough indirect blocks and the stealing of
the deleted extent blocks out of xfs_bmap_split_indlen and into the
caller to prepare for handling delayed allocation of RT extents that
can't easily be stolen.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

fs/xfs/libxfs/xfs_bmap.c

@@ -4831,31 +4831,17 @@ xfs_bmapi_remap(
  * ores == 1). The number of stolen blocks is returned. The availability and
  * subsequent accounting of stolen blocks is the responsibility of the caller.
  */
-static xfs_filblks_t
+static void
 xfs_bmap_split_indlen(
 	xfs_filblks_t			ores,		/* original res. */
 	xfs_filblks_t			*indlen1,	/* ext1 worst indlen */
-	xfs_filblks_t			*indlen2,	/* ext2 worst indlen */
-	xfs_filblks_t			avail)		/* stealable blocks */
+	xfs_filblks_t			*indlen2)	/* ext2 worst indlen */
 {
 	xfs_filblks_t			len1 = *indlen1;
 	xfs_filblks_t			len2 = *indlen2;
 	xfs_filblks_t			nres = len1 + len2; /* new total res. */
-	xfs_filblks_t			stolen = 0;
 	xfs_filblks_t			resfactor;
 
-	/*
-	 * Steal as many blocks as we can to try and satisfy the worst case
-	 * indlen for both new extents.
-	 */
-	if (ores < nres && avail)
-		stolen = XFS_FILBLKS_MIN(nres - ores, avail);
-	ores += stolen;
-
-	 /* nothing else to do if we've satisfied the new reservation */
-	if (ores >= nres)
-		return stolen;
-
 	/*
 	 * We can't meet the total required reservation for the two extents.
 	 * Calculate the percent of the overall shortage between both extents
@@ -4900,8 +4886,6 @@ xfs_bmap_split_indlen(
 
 	*indlen1 = len1;
 	*indlen2 = len2;
-
-	return stolen;
 }
 
 int
@@ -4917,7 +4901,7 @@ xfs_bmap_del_extent_delay(
 	struct xfs_bmbt_irec	new;
 	int64_t			da_old, da_new, da_diff = 0;
 	xfs_fileoff_t		del_endoff, got_endoff;
-	xfs_filblks_t		got_indlen, new_indlen, stolen;
+	xfs_filblks_t		got_indlen, new_indlen, stolen = 0;
 	uint32_t		state = xfs_bmap_fork_to_state(whichfork);
 	uint64_t		fdblocks;
 	int			error = 0;
@@ -4996,8 +4980,19 @@ xfs_bmap_del_extent_delay(
 		new_indlen = xfs_bmap_worst_indlen(ip, new.br_blockcount);
 
 		WARN_ON_ONCE(!got_indlen || !new_indlen);
-		stolen = xfs_bmap_split_indlen(da_old, &got_indlen, &new_indlen,
-						       del->br_blockcount);
+		/*
+		 * Steal as many blocks as we can to try and satisfy the worst
+		 * case indlen for both new extents.
+		 */
+		da_new = got_indlen + new_indlen;
+		if (da_new > da_old) {
+			stolen = XFS_FILBLKS_MIN(da_new - da_old,
+						 del->br_blockcount);
+			da_old += stolen;
+		}
+		if (da_new > da_old)
+			xfs_bmap_split_indlen(da_old, &got_indlen, &new_indlen);
+		da_new = got_indlen + new_indlen;
 
 		got->br_startblock = nullstartblock((int)got_indlen);
 
@@ -5009,7 +5004,6 @@ xfs_bmap_del_extent_delay(
 		xfs_iext_next(ifp, icur);
 		xfs_iext_insert(ip, icur, &new, state);
 
-		da_new = got_indlen + new_indlen - stolen;
 		del->br_blockcount -= stolen;
 		break;
 	}