Merge tag 'discard-relax-locks-6.10_2024-04-15' of...

Merge tag 'discard-relax-locks-6.10_2024-04-15' of https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux into xfs-6.10-mergeA

xfs: less heavy locks during fstrim

Congratulations!  You have made it to the final patchset of the main
online fsck feature!  This patchset fixes some stalling behavior that I
observed when running FITRIM against large flash-based filesystems with
very heavily fragmented free space data.  In summary -- the current
fstrim implementation optimizes for trimming the largest free extents
first, and holds the AGF lock for the duration of the operation.  This
is great if fstrim is being run as a foreground process by a sysadmin.

For xfs_scrub, however, this isn't so good -- we don't really want to
block on one huge kernel call while reporting no progress information.
We don't want to hold the AGF so long that background processes stall.
These problems are easily fixable by issuing smaller FITRIM calls, but
there's still the problem of walking the entire cntbt.  To solve that
second problem, we introduce a new sub-AG FITRIM implementation.  To
solve the first problem, make it relax the AGF periodically.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

* tag 'discard-relax-locks-6.10_2024-04-15' of https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux:
  xfs: fix performance problems when fstrimming a subset of a fragmented AG

fs/xfs/xfs_discard.c

@@ -145,14 +145,18 @@ xfs_discard_extents(
 	return error;
 }
 
+struct xfs_trim_cur {
+	xfs_agblock_t	start;
+	xfs_extlen_t	count;
+	xfs_agblock_t	end;
+	xfs_extlen_t	minlen;
+	bool		by_bno;
+};
 
 static int
 xfs_trim_gather_extents(
 	struct xfs_perag	*pag,
-	xfs_daddr_t		start,
-	xfs_daddr_t		end,
-	xfs_daddr_t		minlen,
-	struct xfs_alloc_rec_incore *tcur,
+	struct xfs_trim_cur	*tcur,
 	struct xfs_busy_extents	*extents,
 	uint64_t		*blocks_trimmed)
 {
@@ -179,21 +183,26 @@ xfs_trim_gather_extents(
 	if (error)
 		goto out_trans_cancel;
 
-	cur = xfs_cntbt_init_cursor(mp, tp, agbp, pag);
-
-	/*
-	 * Look up the extent length requested in the AGF and start with it.
-	 */
-	if (tcur->ar_startblock == NULLAGBLOCK)
-		error = xfs_alloc_lookup_ge(cur, 0, tcur->ar_blockcount, &i);
-	else
-		error = xfs_alloc_lookup_le(cur, tcur->ar_startblock,
-				tcur->ar_blockcount, &i);
+	if (tcur->by_bno) {
+		/* sub-AG discard request always starts at tcur->start */
+		cur = xfs_bnobt_init_cursor(mp, tp, agbp, pag);
+		error = xfs_alloc_lookup_le(cur, tcur->start, 0, &i);
+		if (!error && !i)
+			error = xfs_alloc_lookup_ge(cur, tcur->start, 0, &i);
+	} else if (tcur->start == 0) {
+		/* first time through a by-len starts with max length */
+		cur = xfs_cntbt_init_cursor(mp, tp, agbp, pag);
+		error = xfs_alloc_lookup_ge(cur, 0, tcur->count, &i);
+	} else {
+		/* nth time through a by-len starts where we left off */
+		cur = xfs_cntbt_init_cursor(mp, tp, agbp, pag);
+		error = xfs_alloc_lookup_le(cur, tcur->start, tcur->count, &i);
+	}
 	if (error)
 		goto out_del_cursor;
 	if (i == 0) {
 		/* nothing of that length left in the AG, we are done */
-		tcur->ar_blockcount = 0;
+		tcur->count = 0;
 		goto out_del_cursor;
 	}
 
@@ -204,8 +213,6 @@ xfs_trim_gather_extents(
 	while (i) {
 		xfs_agblock_t	fbno;
 		xfs_extlen_t	flen;
-		xfs_daddr_t	dbno;
-		xfs_extlen_t	dlen;
 
 		error = xfs_alloc_get_rec(cur, &fbno, &flen, &i);
 		if (error)
@@ -221,38 +228,46 @@ xfs_trim_gather_extents(
 			 * Update the cursor to point at this extent so we
 			 * restart the next batch from this extent.
 			 */
-			tcur->ar_startblock = fbno;
-			tcur->ar_blockcount = flen;
-			break;
-		}
-
-		/*
-		 * use daddr format for all range/len calculations as that is
-		 * the format the range/len variables are supplied in by
-		 * userspace.
-		 */
-		dbno = XFS_AGB_TO_DADDR(mp, pag->pag_agno, fbno);
-		dlen = XFS_FSB_TO_BB(mp, flen);
-
-		/*
-		 * Too small?  Give up.
-		 */
-		if (dlen < minlen) {
-			trace_xfs_discard_toosmall(mp, pag->pag_agno, fbno, flen);
-			tcur->ar_blockcount = 0;
+			tcur->start = fbno;
+			tcur->count = flen;
 			break;
 		}
 
 		/*
 		 * If the extent is entirely outside of the range we are
-		 * supposed to discard skip it.  Do not bother to trim
-		 * down partially overlapping ranges for now.
+		 * supposed to skip it.  Do not bother to trim down partially
+		 * overlapping ranges for now.
 		 */
-		if (dbno + dlen < start || dbno > end) {
+		if (fbno + flen < tcur->start) {
+			trace_xfs_discard_exclude(mp, pag->pag_agno, fbno, flen);
+			goto next_extent;
+		}
+		if (fbno > tcur->end) {
 			trace_xfs_discard_exclude(mp, pag->pag_agno, fbno, flen);
+			if (tcur->by_bno) {
+				tcur->count = 0;
+				break;
+			}
 			goto next_extent;
 		}
 
+		/* Trim the extent returned to the range we want. */
+		if (fbno < tcur->start) {
+			flen -= tcur->start - fbno;
+			fbno = tcur->start;
+		}
+		if (fbno + flen > tcur->end + 1)
+			flen = tcur->end - fbno + 1;
+
+		/* Too small?  Give up. */
+		if (flen < tcur->minlen) {
+			trace_xfs_discard_toosmall(mp, pag->pag_agno, fbno, flen);
+			if (tcur->by_bno)
+				goto next_extent;
+			tcur->count = 0;
+			break;
+		}
+
 		/*
 		 * If any blocks in the range are still busy, skip the
 		 * discard and try again the next time.
@@ -266,7 +281,10 @@ xfs_trim_gather_extents(
 				&extents->extent_list);
 		*blocks_trimmed += flen;
 next_extent:
-		error = xfs_btree_decrement(cur, 0, &i);
+		if (tcur->by_bno)
+			error = xfs_btree_increment(cur, 0, &i);
+		else
+			error = xfs_btree_decrement(cur, 0, &i);
 		if (error)
 			break;
 
@@ -276,7 +294,7 @@ xfs_trim_gather_extents(
 		 * is no more extents to search.
 		 */
 		if (i == 0)
-			tcur->ar_blockcount = 0;
+			tcur->count = 0;
 	}
 
 	/*
@@ -306,17 +324,22 @@ xfs_trim_should_stop(void)
 static int
 xfs_trim_extents(
 	struct xfs_perag	*pag,
-	xfs_daddr_t		start,
-	xfs_daddr_t		end,
-	xfs_daddr_t		minlen,
+	xfs_agblock_t		start,
+	xfs_agblock_t		end,
+	xfs_extlen_t		minlen,
 	uint64_t		*blocks_trimmed)
 {
-	struct xfs_alloc_rec_incore tcur = {
-		.ar_blockcount = pag->pagf_longest,
-		.ar_startblock = NULLAGBLOCK,
+	struct xfs_trim_cur	tcur = {
+		.start		= start,
+		.count		= pag->pagf_longest,
+		.end		= end,
+		.minlen		= minlen,
 	};
 	int			error = 0;
 
+	if (start != 0 || end != pag->block_count)
+		tcur.by_bno = true;
+
 	do {
 		struct xfs_busy_extents	*extents;
 
@@ -330,8 +353,8 @@ xfs_trim_extents(
 		extents->owner = extents;
 		INIT_LIST_HEAD(&extents->extent_list);
 
-		error = xfs_trim_gather_extents(pag, start, end, minlen,
-				&tcur, extents, blocks_trimmed);
+		error = xfs_trim_gather_extents(pag, &tcur, extents,
+				blocks_trimmed);
 		if (error) {
 			kfree(extents);
 			break;
@@ -354,7 +377,7 @@ xfs_trim_extents(
 		if (xfs_trim_should_stop())
 			break;
 
-	} while (tcur.ar_blockcount != 0);
+	} while (tcur.count != 0);
 
 	return error;
 
@@ -378,8 +401,10 @@ xfs_ioc_trim(
 	unsigned int		granularity =
 		bdev_discard_granularity(mp->m_ddev_targp->bt_bdev);
 	struct fstrim_range	range;
-	xfs_daddr_t		start, end, minlen;
-	xfs_agnumber_t		agno;
+	xfs_daddr_t		start, end;
+	xfs_extlen_t		minlen;
+	xfs_agnumber_t		start_agno, end_agno;
+	xfs_agblock_t		start_agbno, end_agbno;
 	uint64_t		blocks_trimmed = 0;
 	int			error, last_error = 0;
 
@@ -399,7 +424,8 @@ xfs_ioc_trim(
 		return -EFAULT;
 
 	range.minlen = max_t(u64, granularity, range.minlen);
-	minlen = BTOBB(range.minlen);
+	minlen = XFS_B_TO_FSB(mp, range.minlen);
+
 	/*
 	 * Truncating down the len isn't actually quite correct, but using
 	 * BBTOB would mean we trivially get overflows for values
@@ -413,15 +439,21 @@ xfs_ioc_trim(
 		return -EINVAL;
 
 	start = BTOBB(range.start);
-	end = start + BTOBBT(range.len) - 1;
+	end = min_t(xfs_daddr_t, start + BTOBBT(range.len),
+		    XFS_FSB_TO_BB(mp, mp->m_sb.sb_dblocks)) - 1;
+
+	start_agno = xfs_daddr_to_agno(mp, start);
+	start_agbno = xfs_daddr_to_agbno(mp, start);
+	end_agno = xfs_daddr_to_agno(mp, end);
+	end_agbno = xfs_daddr_to_agbno(mp, end);
 
-	if (end > XFS_FSB_TO_BB(mp, mp->m_sb.sb_dblocks) - 1)
-		end = XFS_FSB_TO_BB(mp, mp->m_sb.sb_dblocks) - 1;
+	for_each_perag_range(mp, start_agno, end_agno, pag) {
+		xfs_agblock_t	agend = pag->block_count;
 
-	agno = xfs_daddr_to_agno(mp, start);
-	for_each_perag_range(mp, agno, xfs_daddr_to_agno(mp, end), pag) {
-		error = xfs_trim_extents(pag, start, end, minlen,
-					  &blocks_trimmed);
+		if (start_agno == end_agno)
+			agend = end_agbno;
+		error = xfs_trim_extents(pag, start_agbno, agend, minlen,
+				&blocks_trimmed);
 		if (error)
 			last_error = error;
 
@@ -429,6 +461,7 @@ xfs_ioc_trim(
 			xfs_perag_rele(pag);
 			break;
 		}
+		start_agbno = 0;
 	}
 
 	if (last_error)