Re: FAILED: patch "[PATCH] btrfs: do not zero f_bavail if we have available space" failed to apply to 5.4-stable tree

[Sasha Levin <sashal@kernel.org>]

On Sun, Feb 09, 2020 at 12:33:33PM +0100, gregkh@linuxfoundation.org wrote:
>
>The patch below does not apply to the 5.4-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,
>
>greg k-h
>
>------------------ original commit in Linus's tree ------------------
>
>From d55966c4279bfc6a0cf0b32bf13f5df228a1eeb6 Mon Sep 17 00:00:00 2001
>From: Josef Bacik <josef@toxicpanda.com>
>Date: Fri, 31 Jan 2020 09:31:05 -0500
>Subject: [PATCH] btrfs: do not zero f_bavail if we have available space
>
>There was some logic added a while ago to clear out f_bavail in statfs()
>if we did not have enough free metadata space to satisfy our global
>reserve.  This was incorrect at the time, however didn't really pose a
>problem for normal file systems because we would often allocate chunks
>if we got this low on free metadata space, and thus wouldn't really hit
>this case unless we were actually full.
>
>Fast forward to today and now we are much better about not allocating
>metadata chunks all of the time.  Couple this with d792b0f19711 ("btrfs:
>always reserve our entire size for the global reserve") which now means
>we'll easily have a larger global reserve than our free space, we are
>now more likely to trip over this while still having plenty of space.
>
>Fix this by skipping this logic if the global rsv's space_info is not
>full.  space_info->full is 0 unless we've attempted to allocate a chunk
>for that space_info and that has failed.  If this happens then the space
>for the global reserve is definitely sacred and we need to report
>b_avail == 0, but before then we can just use our calculated b_avail.
>
>Reported-by: Martin Steigerwald <martin@lichtvoll.de>
>Fixes: ca8a51b3a979 ("btrfs: statfs: report zero available if metadata are exhausted")
>CC: stable@vger.kernel.org # 4.5+
>Reviewed-by: Qu Wenruo <wqu@suse.com>
>Tested-By: Martin Steigerwald <martin@lichtvoll.de>
>Signed-off-by: Josef Bacik <josef@toxicpanda.com>
>Reviewed-by: David Sterba <dsterba@suse.com>
>Signed-off-by: David Sterba <dsterba@suse.com>

This one is queued up already :)

-- 
Thanks,
Sasha