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FAILED: patch "[PATCH] Btrfs: fix early ENOSPC due to delalloc" failed to apply to 4.9-stable tree

PATCH [email protected] 2 participants 2 messages Aug 1, 2017 – Aug 4, 2017

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#0 lore raw

The patch below does not apply to the 4.9-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 <[email protected]>.

thanks,

greg k-h

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

Quoted 1 line

From 17024ad0a0fdfcfe53043afb969b813d3e020c21 Mon Sep 17 00:00:00 2001

From: Omar Sandoval <[email protected]>
Date: Thu, 20 Jul 2017 15:10:35 -0700
Subject: [PATCH] Btrfs: fix early ENOSPC due to delalloc

If a lot of metadata is reserved for outstanding delayed allocations, we rely on shrink_delalloc() to reclaim metadata space in order to fulfill reservation tickets. However, shrink_delalloc() has a shortcut where if it determines that space can be overcommitted, it will stop early. This made sense before the ticketed enospc system, but now it means that shrink_delalloc() will often not reclaim enough space to fulfill any tickets, leading to an early ENOSPC. (Reservation tickets don't care about being able to overcommit, they need every byte accounted for.)

Fix it by getting rid of the shortcut so that shrink_delalloc() reclaims all of the metadata it is supposed to. This fixes early ENOSPCs we were seeing when doing a btrfs receive to populate a new filesystem, as well as early ENOSPCs Christoph saw when doing a big cp -r onto Btrfs.

Fixes 957780eb2788 ("Btrfs: introduce ticketed enospc infrastructure")
fs/btrfs/extent-tree.c +0 -4
index a6635f07b8f1..e3b0b4196d3d 100644
@@ -4825,10 +4825,6 @@ static void shrink_delalloc(struct btrfs_fs_info *fs_info, u64 to_reclaim,
 		else
 			flush = BTRFS_RESERVE_NO_FLUSH;
 		spin_lock(&space_info->lock);
-		if (can_overcommit(fs_info, space_info, orig, flush, false)) {
-			spin_unlock(&space_info->lock);
-			break;
-		}
 		if (list_empty(&space_info->tickets) &&
 		    list_empty(&space_info->priority_tickets)) {
 			spin_unlock(&space_info->lock);
#1 lore raw
Quoted 44 lines · On 08/01/17 03:06, [email protected] wrote:

The patch below does not apply to the 4.9-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 <[email protected]>.

thanks,

greg k-h

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

From 17024ad0a0fdfcfe53043afb969b813d3e020c21 Mon Sep 17 00:00:00 2001
From: Omar Sandoval <[email protected]>
Date: Thu, 20 Jul 2017 15:10:35 -0700
Subject: [PATCH] Btrfs: fix early ENOSPC due to delalloc

If a lot of metadata is reserved for outstanding delayed allocations, we rely on shrink_delalloc() to reclaim metadata space in order to fulfill reservation tickets. However, shrink_delalloc() has a shortcut where if it determines that space can be overcommitted, it will stop early. This made sense before the ticketed enospc system, but now it means that shrink_delalloc() will often not reclaim enough space to fulfill any tickets, leading to an early ENOSPC. (Reservation tickets don't care about being able to overcommit, they need every byte accounted for.)

Fix it by getting rid of the shortcut so that shrink_delalloc() reclaims all of the metadata it is supposed to. This fixes early ENOSPCs we were seeing when doing a btrfs receive to populate a new filesystem, as well as early ENOSPCs Christoph saw when doing a big cp -r onto Btrfs.

Fixes 957780eb2788 ("Btrfs: introduce ticketed enospc infrastructure")
fs/btrfs/extent-tree.c +0 -0
index a6635f07b8f1..e3b0b4196d3d 100644

fs/btrfs/extent-tree.c static void shrink_delalloc(struct btrfs_fs_info *fs_info, u64 to_reclaim, · line 4830

Quoted 10 lines
fs/btrfs/extent-tree.c +0 -4
@@ -4825,10 +4825,6 @@ static void shrink_delalloc(struct btrfs_fs_info *fs_info, u64 to_reclaim,
 		else
 			flush = BTRFS_RESERVE_NO_FLUSH;
 		spin_lock(&space_info->lock);
-		if (can_overcommit(fs_info, space_info, orig, flush, false)) {
-			spin_unlock(&space_info->lock);
-			break;
-		}
 		if (list_empty(&space_info->tickets) &&
 		    list_empty(&space_info->priority_tickets)) {
 			spin_unlock(&space_info->lock);

This is kind of important to have, so attached is the backport for 4.9.40 that I've been using; I just rediffed it to apply cleanly. For 4.12.x someone else needs to step up.

-h

fs/btrfs/extent-tree.c +0 -4
diff -rup linux-4.9.40/fs/btrfs/extent-tree.c linux-4.9.40+/fs/btrfs/extent-tree.c
@@ -4759,10 +4759,6 @@ skip_async:
 		else
 			flush = BTRFS_RESERVE_NO_FLUSH;
 		spin_lock(&space_info->lock);
-		if (can_overcommit(root, space_info, orig, flush)) {
-			spin_unlock(&space_info->lock);
-			break;
-		}
 		if (list_empty(&space_info->tickets) &&
 		    list_empty(&space_info->priority_tickets)) {
 			spin_unlock(&space_info->lock);