xfs: hoist refcount record merge predicates

Source kernel commit: 9d720a5a658f5135861773f26e927449bef93d61

Hoist these multiline conditionals into separate static inline helpers
to improve readability and set the stage for corruption fixes that will
be introduced in the next patch.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Xiao Yang <yangx.jy@fujitsu.com>
Signed-off-by: Carlos Maiolino <cem@kernel.org>

1 files changed, 113 insertions, 16 deletions

diff --git a/libxfs/xfs_refcount.c b/libxfs/xfs_refcount.c
index 64e66861b8..f6167c5fc1 100644
--- a/libxfs/xfs_refcount.c
+++ b/libxfs/xfs_refcount.c
@@ -814,11 +814,119 @@ out_error:
 /* Is this extent valid? */
 static inline bool
 xfs_refc_valid(
-	struct xfs_refcount_irec	*rc)
+	const struct xfs_refcount_irec	*rc)
 {
 	return rc->rc_startblock != NULLAGBLOCK;
 }
 
+static inline bool
+xfs_refc_want_merge_center(
+	const struct xfs_refcount_irec	*left,
+	const struct xfs_refcount_irec	*cleft,
+	const struct xfs_refcount_irec	*cright,
+	const struct xfs_refcount_irec	*right,
+	bool				cleft_is_cright,
+	enum xfs_refc_adjust_op		adjust,
+	unsigned long long		*ulenp)
+{
+	unsigned long long		ulen = left->rc_blockcount;
+
+	/*
+	 * To merge with a center record, both shoulder records must be
+	 * adjacent to the record we want to adjust.  This is only true if
+	 * find_left and find_right made all four records valid.
+	 */
+	if (!xfs_refc_valid(left)  || !xfs_refc_valid(right) ||
+	    !xfs_refc_valid(cleft) || !xfs_refc_valid(cright))
+		return false;
+
+	/* There must only be one record for the entire range. */
+	if (!cleft_is_cright)
+		return false;
+
+	/* The shoulder record refcounts must match the new refcount. */
+	if (left->rc_refcount != cleft->rc_refcount + adjust)
+		return false;
+	if (right->rc_refcount != cleft->rc_refcount + adjust)
+		return false;
+
+	/*
+	 * The new record cannot exceed the max length.  ulen is a ULL as the
+	 * individual record block counts can be up to (u32 - 1) in length
+	 * hence we need to catch u32 addition overflows here.
+	 */
+	ulen += cleft->rc_blockcount + right->rc_blockcount;
+	if (ulen >= MAXREFCEXTLEN)
+		return false;
+
+	*ulenp = ulen;
+	return true;
+}
+
+static inline bool
+xfs_refc_want_merge_left(
+	const struct xfs_refcount_irec	*left,
+	const struct xfs_refcount_irec	*cleft,
+	enum xfs_refc_adjust_op		adjust)
+{
+	unsigned long long		ulen = left->rc_blockcount;
+
+	/*
+	 * For a left merge, the left shoulder record must be adjacent to the
+	 * start of the range.  If this is true, find_left made left and cleft
+	 * contain valid contents.
+	 */
+	if (!xfs_refc_valid(left) || !xfs_refc_valid(cleft))
+		return false;
+
+	/* Left shoulder record refcount must match the new refcount. */
+	if (left->rc_refcount != cleft->rc_refcount + adjust)
+		return false;
+
+	/*
+	 * The new record cannot exceed the max length.  ulen is a ULL as the
+	 * individual record block counts can be up to (u32 - 1) in length
+	 * hence we need to catch u32 addition overflows here.
+	 */
+	ulen += cleft->rc_blockcount;
+	if (ulen >= MAXREFCEXTLEN)
+		return false;
+
+	return true;
+}
+
+static inline bool
+xfs_refc_want_merge_right(
+	const struct xfs_refcount_irec	*cright,
+	const struct xfs_refcount_irec	*right,
+	enum xfs_refc_adjust_op		adjust)
+{
+	unsigned long long		ulen = right->rc_blockcount;
+
+	/*
+	 * For a right merge, the right shoulder record must be adjacent to the
+	 * end of the range.  If this is true, find_right made cright and right
+	 * contain valid contents.
+	 */
+	if (!xfs_refc_valid(right) || !xfs_refc_valid(cright))
+		return false;
+
+	/* Right shoulder record refcount must match the new refcount. */
+	if (right->rc_refcount != cright->rc_refcount + adjust)
+		return false;
+
+	/*
+	 * The new record cannot exceed the max length.  ulen is a ULL as the
+	 * individual record block counts can be up to (u32 - 1) in length
+	 * hence we need to catch u32 addition overflows here.
+	 */
+	ulen += cright->rc_blockcount;
+	if (ulen >= MAXREFCEXTLEN)
+		return false;
+
+	return true;
+}
+
 /*
  * Try to merge with any extents on the boundaries of the adjustment range.
  */
@@ -860,23 +968,15 @@ xfs_refcount_merge_extents(
 		 (cleft.rc_blockcount == cright.rc_blockcount);
 
 	/* Try to merge left, cleft, and right.  cleft must == cright. */
-	ulen = (unsigned long long)left.rc_blockcount + cleft.rc_blockcount +
-			right.rc_blockcount;
-	if (xfs_refc_valid(&left) && xfs_refc_valid(&right) &&
-	    xfs_refc_valid(&cleft) && xfs_refc_valid(&cright) && cequal &&
-	    left.rc_refcount == cleft.rc_refcount + adjust &&
-	    right.rc_refcount == cleft.rc_refcount + adjust &&
-	    ulen < MAXREFCEXTLEN) {
+	if (xfs_refc_want_merge_center(&left, &cleft, &cright, &right, cequal,
+				adjust, &ulen)) {
 		*shape_changed = true;
 		return xfs_refcount_merge_center_extents(cur, &left, &cleft,
 				&right, ulen, aglen);
 	}
 
 	/* Try to merge left and cleft. */
-	ulen = (unsigned long long)left.rc_blockcount + cleft.rc_blockcount;
-	if (xfs_refc_valid(&left) && xfs_refc_valid(&cleft) &&
-	    left.rc_refcount == cleft.rc_refcount + adjust &&
-	    ulen < MAXREFCEXTLEN) {
+	if (xfs_refc_want_merge_left(&left, &cleft, adjust)) {
 		*shape_changed = true;
 		error = xfs_refcount_merge_left_extent(cur, &left, &cleft,
 				agbno, aglen);
@@ -892,10 +992,7 @@ xfs_refcount_merge_extents(
 	}
 
 	/* Try to merge cright and right. */
-	ulen = (unsigned long long)right.rc_blockcount + cright.rc_blockcount;
-	if (xfs_refc_valid(&right) && xfs_refc_valid(&cright) &&
-	    right.rc_refcount == cright.rc_refcount + adjust &&
-	    ulen < MAXREFCEXTLEN) {
+	if (xfs_refc_want_merge_right(&cright, &right, adjust)) {
 		*shape_changed = true;
 		return xfs_refcount_merge_right_extent(cur, &right, &cright,
 				aglen);