Linux 4.14.95

[thirdparty/kernel/stable-queue.git] / releases / 4.5.7 / btrfs-make-state-preallocation-more-speculative-in-__set_extent_bit.patch

From 059f791c6bbaba72dc3c1bd6e2657aacc8552849 Mon Sep 17 00:00:00 2001
From: David Sterba <dsterba@suse.com>
Date: Wed, 27 Apr 2016 01:03:45 +0200
Subject: btrfs: make state preallocation more speculative in __set_extent_bit

From: David Sterba <dsterba@suse.com>

commit 059f791c6bbaba72dc3c1bd6e2657aacc8552849 upstream.

Similar to __clear_extent_bit, do not fail if the state preallocation
fails as we might not need it. One less BUG_ON.

Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/btrfs/extent_io.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -875,8 +875,14 @@ __set_extent_bit(struct extent_io_tree *
 	bits |= EXTENT_FIRST_DELALLOC;
 again:
 	if (!prealloc && gfpflags_allow_blocking(mask)) {
+		/*
+		 * Don't care for allocation failure here because we might end
+		 * up not needing the pre-allocated extent state at all, which
+		 * is the case if we only have in the tree extent states that
+		 * cover our input range and don't cover too any other range.
+		 * If we end up needing a new extent state we allocate it later.
+		 */
 		prealloc = alloc_extent_state(mask);
-		BUG_ON(!prealloc);
 	}
 
 	spin_lock(&tree->lock);