From: Christoph Hellwig <hch@infradead.org>
To: Jan Prusakowski <jprusakowski@google.com>
Cc: jaegeuk@kernel.org, zlang@kernel.org, fstests@vger.kernel.org,
linux-f2fs-devel@lists.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH] generic/064: allow 50 extents on F2FS after fcollapse
Date: Wed, 24 Jun 2026 00:46:01 -0700 [thread overview]
Message-ID: <ajuLORVplOvEXvnI@infradead.org> (raw)
In-Reply-To: <20260622070438.1542638-1-jprusakowski@google.com>
On Mon, Jun 22, 2026 at 07:04:38AM +0000, Jan Prusakowski wrote:
> On F2FS, generic/064 fails with "extents mismatched before = 1 after =
> 50" following multiple fcollapse (collapse range) operations.
>
> To ensure crash consistency and checkpoint integrity, F2FS forbids
> in-place SSR (Summary Standalone Replacement) overwrites on valid
> checkpointed blocks. When collapse range shifts blocks, F2FS allocates
> new data pages in LFS mode (out-of-place log writes). As a result,
> sequential collapse range calls rewrite shifted blocks at new log
> locations, intentionally leaving the file with 50 extents.
This sounds odd. The test allocates a contigous range and then just does
insert/collapse on it, which should not lead to any new data block
allocations. Given that the test works fine on zoned XFS and btrfs
with strict out of place write policies we know it does not require
overwriting blocks to work as well.
So I think something is fishy in f2fs if needs to allocate data blocks
here.
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WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@infradead.org>
To: Jan Prusakowski <jprusakowski@google.com>
Cc: fstests@vger.kernel.org, zlang@kernel.org, jaegeuk@kernel.org,
linux-f2fs-devel@lists.sourceforge.net
Subject: Re: [PATCH] generic/064: allow 50 extents on F2FS after fcollapse
Date: Wed, 24 Jun 2026 00:46:01 -0700 [thread overview]
Message-ID: <ajuLORVplOvEXvnI@infradead.org> (raw)
In-Reply-To: <20260622070438.1542638-1-jprusakowski@google.com>
On Mon, Jun 22, 2026 at 07:04:38AM +0000, Jan Prusakowski wrote:
> On F2FS, generic/064 fails with "extents mismatched before = 1 after =
> 50" following multiple fcollapse (collapse range) operations.
>
> To ensure crash consistency and checkpoint integrity, F2FS forbids
> in-place SSR (Summary Standalone Replacement) overwrites on valid
> checkpointed blocks. When collapse range shifts blocks, F2FS allocates
> new data pages in LFS mode (out-of-place log writes). As a result,
> sequential collapse range calls rewrite shifted blocks at new log
> locations, intentionally leaving the file with 50 extents.
This sounds odd. The test allocates a contigous range and then just does
insert/collapse on it, which should not lead to any new data block
allocations. Given that the test works fine on zoned XFS and btrfs
with strict out of place write policies we know it does not require
overwriting blocks to work as well.
So I think something is fishy in f2fs if needs to allocate data blocks
here.
next prev parent reply other threads:[~2026-06-24 7:46 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-22 7:04 [PATCH] generic/064: allow 50 extents on F2FS after fcollapse Jan Prusakowski
2026-06-22 7:04 ` [f2fs-dev] " Jan Prusakowski via Linux-f2fs-devel
2026-06-23 8:46 ` Chao Yu
2026-06-23 8:46 ` Chao Yu via Linux-f2fs-devel
2026-06-24 7:46 ` Christoph Hellwig [this message]
2026-06-24 7:46 ` Christoph Hellwig
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