Commit 94896196 authored by Darrick J. Wong's avatar Darrick J. Wong
Browse files

Merge tag 'maxrefcount-fixes-6.2_2022-12-01' of... 

Merge tag 'maxrefcount-fixes-6.2_2022-12-01' of git://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux

 into xfs-6.2-mergeD

xfs: fix broken MAXREFCOUNT handling

This series fixes a bug in the refcount code where we don't merge
records correctly if the refcount is hovering around MAXREFCOUNT.  This
fixes regressions in xfs/179 when fsdax is enabled.  xfs/179 itself will
be modified to exploit the bug through the pagecache path.

Signed-off-by: default avatarDarrick J. Wong <djwong@kernel.org>

* tag 'maxrefcount-fixes-6.2_2022-12-01' of git://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux:
  xfs: estimate post-merge refcounts correctly
  xfs: hoist refcount record merge predicates
parents 575689fc b25d1984

fs/xfs/libxfs/xfs_refcount.c

+130 −16
Original line number Diff line number Diff line
@@ -815,11 +815,136 @@ xfs_refcount_find_right_extents( 
/* 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 xfs_nlink_t

xfs_refc_merge_refcount(

	const struct xfs_refcount_irec	*irec,

	enum xfs_refc_adjust_op		adjust)

{

	/* Once a record hits MAXREFCOUNT, it is pinned there forever */

	if (irec->rc_refcount == MAXREFCOUNT)

		return MAXREFCOUNT;

	return irec->rc_refcount + adjust;

}



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;

	xfs_nlink_t			new_refcount;



	/*

	 * 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. */

	new_refcount = xfs_refc_merge_refcount(cleft, adjust);

	if (left->rc_refcount != new_refcount)

		return false;

	if (right->rc_refcount != new_refcount)

		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;

	xfs_nlink_t			new_refcount;



	/*

	 * 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. */

	new_refcount = xfs_refc_merge_refcount(cleft, adjust);

	if (left->rc_refcount != new_refcount)

		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;

	xfs_nlink_t			new_refcount;



	/*

	 * 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. */

	new_refcount = xfs_refc_merge_refcount(cright, adjust);

	if (right->rc_refcount != new_refcount)

		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.

 */
@@ -861,23 +986,15 @@ 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);
@@ -893,10 +1010,7 @@ 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);