This is a note to let you know that I've just added the patch titled
Revert "btrfs: compression: don't try to compress if we don't have enough pages"
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
revert-btrfs-compression-don-t-try-to-compress-if-we-don-t-have-enough-pages.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 4e9655763b82a91e4c341835bb504a2b1590f984 Mon Sep 17 00:00:00 2001
From: Qu Wenruo <wqu@xxxxxxxx>
Date: Wed, 25 Aug 2021 13:41:42 +0800
Subject: Revert "btrfs: compression: don't try to compress if we don't have enough pages"
From: Qu Wenruo <wqu@xxxxxxxx>
commit 4e9655763b82a91e4c341835bb504a2b1590f984 upstream.
This reverts commit f2165627319ffd33a6217275e5690b1ab5c45763.
[BUG]
It's no longer possible to create compressed inline extent after commit
f2165627319f ("btrfs: compression: don't try to compress if we don't
have enough pages").
[CAUSE]
For compression code, there are several possible reasons we have a range
that needs to be compressed while it's no more than one page.
- Compressed inline write
The data is always smaller than one sector and the test lacks the
condition to properly recognize a non-inline extent.
- Compressed subpage write
For the incoming subpage compressed write support, we require page
alignment of the delalloc range.
And for 64K page size, we can compress just one page into smaller
sectors.
For those reasons, the requirement for the data to be more than one page
is not correct, and is already causing regression for compressed inline
data writeback. The idea of skipping one page to avoid wasting CPU time
could be revisited in the future.
[FIX]
Fix it by reverting the offending commit.
Reported-by: Zygo Blaxell <ce3g8jdj@xxxxxxxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/linux-btrfs/afa2742.c084f5d6.17b6b08dffc@xxxxxxxxxxxx
Fixes: f2165627319f ("btrfs: compression: don't try to compress if we don't have enough pages")
CC: stable@xxxxxxxxxxxxxxx # 4.4+
Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
Reviewed-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/btrfs/inode.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -476,7 +476,7 @@ again:
* inode has not been flagged as nocompress. This flag can
* change at any time if we discover bad compression ratios.
*/
- if (nr_pages > 1 && inode_need_compress(inode)) {
+ if (inode_need_compress(inode)) {
WARN_ON(pages);
pages = kcalloc(nr_pages, sizeof(struct page *), GFP_NOFS);
if (!pages) {
Patches currently in stable-queue which might be from wqu@xxxxxxxx are
queue-4.4/revert-btrfs-compression-don-t-try-to-compress-if-we-don-t-have-enough-pages.patch
