FAILED: Patch "btrfs: fix periodic reclaim condition" failed to apply to 6.12-stable tree

[Sasha Levin <sashal@kernel.org>]

The patch below does not apply to the 6.12-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

Thanks,
Sasha

------------------ original commit in Linus's tree ------------------

From 19eff93dc738e8afaa59cb374b44bb5a162e6c2d Mon Sep 17 00:00:00 2001
From: Sun YangKai <sunk67188@gmail.com>
Date: Wed, 14 Jan 2026 11:47:02 +0800
Subject: [PATCH] btrfs: fix periodic reclaim condition

Problems with current implementation:

1. reclaimable_bytes is signed while chunk_sz is unsigned, causing
   negative reclaimable_bytes to trigger reclaim unexpectedly

2. The "space must be freed between scans" assumption breaks the
   two-scan requirement: first scan marks block groups, second scan
   reclaims them. Without the second scan, no reclamation occurs.

Instead, track actual reclaim progress: pause reclaim when block groups
will be reclaimed, and resume only when progress is made. This ensures
reclaim continues until no further progress can be made. And resume
periodic reclaim when there's enough free space.

And we take care if reclaim is making any progress now, so it's
unnecessary to set periodic_reclaim_ready to false when failed to reclaim
a block group.

Fixes: 813d4c6422516 ("btrfs: prevent pathological periodic reclaim loops")
CC: stable@vger.kernel.org # 6.12+
Suggested-by: Boris Burkov <boris@bur.io>
Reviewed-by: Boris Burkov <boris@bur.io>
Signed-off-by: Sun YangKai <sunk67188@gmail.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/block-group.c |  6 ++++--
 fs/btrfs/space-info.c  | 21 ++++++++++++---------
 2 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
index 4fc4d49910bf2..6c6133584196b 100644
--- a/fs/btrfs/block-group.c
+++ b/fs/btrfs/block-group.c
@@ -1889,6 +1889,7 @@ void btrfs_reclaim_bgs_work(struct work_struct *work)
 	while (!list_empty(&fs_info->reclaim_bgs)) {
 		u64 used;
 		u64 reserved;
+		u64 old_total;
 		int ret = 0;
 
 		bg = list_first_entry(&fs_info->reclaim_bgs,
@@ -1954,6 +1955,7 @@ void btrfs_reclaim_bgs_work(struct work_struct *work)
 		}
 
 		spin_unlock(&bg->lock);
+		old_total = space_info->total_bytes;
 		spin_unlock(&space_info->lock);
 
 		/*
@@ -2006,14 +2008,14 @@ void btrfs_reclaim_bgs_work(struct work_struct *work)
 			reserved = 0;
 			spin_lock(&space_info->lock);
 			space_info->reclaim_errors++;
-			if (READ_ONCE(space_info->periodic_reclaim))
-				space_info->periodic_reclaim_ready = false;
 			spin_unlock(&space_info->lock);
 		}
 		spin_lock(&space_info->lock);
 		space_info->reclaim_count++;
 		space_info->reclaim_bytes += used;
 		space_info->reclaim_bytes += reserved;
+		if (space_info->total_bytes < old_total)
+			btrfs_set_periodic_reclaim_ready(space_info, true);
 		spin_unlock(&space_info->lock);
 
 next:
diff --git a/fs/btrfs/space-info.c b/fs/btrfs/space-info.c
index ebe97d6d67d3a..bc493243f777d 100644
--- a/fs/btrfs/space-info.c
+++ b/fs/btrfs/space-info.c
@@ -2098,11 +2098,11 @@ static bool is_reclaim_urgent(struct btrfs_space_info *space_info)
 	return unalloc < data_chunk_size;
 }
 
-static void do_reclaim_sweep(struct btrfs_space_info *space_info, int raid)
+static bool do_reclaim_sweep(struct btrfs_space_info *space_info, int raid)
 {
 	struct btrfs_block_group *bg;
 	int thresh_pct;
-	bool try_again = true;
+	bool will_reclaim = false;
 	bool urgent;
 
 	spin_lock(&space_info->lock);
@@ -2120,7 +2120,7 @@ static void do_reclaim_sweep(struct btrfs_space_info *space_info, int raid)
 		spin_lock(&bg->lock);
 		thresh = mult_perc(bg->length, thresh_pct);
 		if (bg->used < thresh && bg->reclaim_mark) {
-			try_again = false;
+			will_reclaim = true;
 			reclaim = true;
 		}
 		bg->reclaim_mark++;
@@ -2137,12 +2137,13 @@ static void do_reclaim_sweep(struct btrfs_space_info *space_info, int raid)
 	 * If we have any staler groups, we don't touch the fresher ones, but if we
 	 * really need a block group, do take a fresh one.
 	 */
-	if (try_again && urgent) {
-		try_again = false;
+	if (!will_reclaim && urgent) {
+		urgent = false;
 		goto again;
 	}
 
 	up_read(&space_info->groups_sem);
+	return will_reclaim;
 }
 
 void btrfs_space_info_update_reclaimable(struct btrfs_space_info *space_info, s64 bytes)
@@ -2152,7 +2153,8 @@ void btrfs_space_info_update_reclaimable(struct btrfs_space_info *space_info, s6
 	lockdep_assert_held(&space_info->lock);
 	space_info->reclaimable_bytes += bytes;
 
-	if (space_info->reclaimable_bytes >= chunk_sz)
+	if (space_info->reclaimable_bytes > 0 &&
+	    space_info->reclaimable_bytes >= chunk_sz)
 		btrfs_set_periodic_reclaim_ready(space_info, true);
 }
 
@@ -2179,7 +2181,6 @@ static bool btrfs_should_periodic_reclaim(struct btrfs_space_info *space_info)
 
 	spin_lock(&space_info->lock);
 	ret = space_info->periodic_reclaim_ready;
-	btrfs_set_periodic_reclaim_ready(space_info, false);
 	spin_unlock(&space_info->lock);
 
 	return ret;
@@ -2193,8 +2194,10 @@ void btrfs_reclaim_sweep(const struct btrfs_fs_info *fs_info)
 	list_for_each_entry(space_info, &fs_info->space_info, list) {
 		if (!btrfs_should_periodic_reclaim(space_info))
 			continue;
-		for (raid = 0; raid < BTRFS_NR_RAID_TYPES; raid++)
-			do_reclaim_sweep(space_info, raid);
+		for (raid = 0; raid < BTRFS_NR_RAID_TYPES; raid++) {
+			if (do_reclaim_sweep(space_info, raid))
+				btrfs_set_periodic_reclaim_ready(space_info, false);
+		}
 	}
 }
 
-- 
2.51.0