From: David Sterba <dsterba@suse.cz>
To: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
Cc: Chris Mason <clm@fb.com>, Josef Bacik <josef@toxicpanda.com>,
David Sterba <dsterba@suse.com>, Qu Wenruo <wqu@suse.com>,
linux-btrfs@vger.kernel.org, kernel-team@meta.com,
Neal Gompa <neal@gompa.dev>
Subject: Re: [PATCH] btrfs: fallback if compressed IO fails for ENOSPC
Date: Tue, 9 Apr 2024 13:27:43 +0200 [thread overview]
Message-ID: <20240409112743.GC3492@twin.jikos.cz> (raw)
In-Reply-To: <4607d44ee4cf72a302d3adeba5d0ae99518a5f36.1712391866.git.sweettea-kernel@dorminy.me>
On Sat, Apr 06, 2024 at 04:45:02AM -0400, Sweet Tea Dorminy wrote:
> In commit b4ccace878f4 ("btrfs: refactor submit_compressed_extents()"), if
> an async extent compressed but failed to find enough space, we changed
> from falling back to an uncompressed write to just failing the write
> altogether. The principle was that if there's not enough space to write
> the compressed version of the data, there can't possibly be enough space
> to write the larger, uncompressed version of the data.
>
> However, this isn't necessarily true: due to fragmentation, there could
> be enough discontiguous free blocks to write the uncompressed version,
> but not enough contiguous free blocks to write the smaller but
> unsplittable compressed version.
>
> This has occurred to an internal workload which relied on write()'s
> return value indicating there was space. While rare, it has happened a
> few times.
>
> Thus, in order to prevent early ENOSPC, re-add a fallback to
> uncompressed writing.
>
> Fixes: b4ccace878f4 ("btrfs: refactor submit_compressed_extents()")
> Co-developed-by: Neal Gompa <neal@gompa.dev>
> Signed-off-by: Neal Gompa <neal@gompa.dev>
> Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
Reviewed-by: David Sterba <dsterba@suse.com>
prev parent reply other threads:[~2024-04-09 11:35 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-06 8:45 [PATCH] btrfs: fallback if compressed IO fails for ENOSPC Sweet Tea Dorminy
2024-04-06 9:02 ` Qu Wenruo
2024-04-09 11:27 ` David Sterba [this message]
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