From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E978E19D065 for ; Mon, 27 Oct 2025 08:04:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761552275; cv=none; b=U/E6DctlSlEPHgvSZkkmSn2ihZnjFDZ227KS36TeLI6NspJEUyOjdbc1kXrH8fe6nksp2AcIwdeVs2nsVjuCsraWxLPxFNBPvBn8PDy2wuOXEtnAHbW0aAmVDyKvJu9zhe70YHpPizhl2HisIvW410hqy85pwtqn73MP/m0AmHQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761552275; c=relaxed/simple; bh=sgCne/ELFZaA17TmEA7gqxd4vbE9iXyIeLCoG+vVFZs=; h=Message-ID:Date:MIME-Version:Cc:Subject:To:References:From: In-Reply-To:Content-Type; b=LOH80y6o28uH5z/8e7SmxWIlIP8GJ9gFDV7yU8oFwGsfeE5+mCvRw9t9qsMP07UMHQGNPfzKkskF77JIac/pNfKTNL0VBsF1iS5S+7LOH+BI59+2LNpqAqF2VSWpME6R93VFJDZR6docWE6wbCiCWv8KR8clCOU/R9GWumU3+Xs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=hkHf8N6B; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="hkHf8N6B" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7F0EDC4CEF1; Mon, 27 Oct 2025 08:04:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1761552274; bh=sgCne/ELFZaA17TmEA7gqxd4vbE9iXyIeLCoG+vVFZs=; h=Date:Cc:Subject:To:References:From:In-Reply-To:From; b=hkHf8N6BVg6dYETC1WA1bEveoZtCvBl2zq1xyFdk1nRHk6jwUhs8COhi7NDshHa4B tDf3KWacA6UyG3zU+dIHjhusWdHCZbE0bsfEXEFTVJkX387CxPzwvjZiUuA++Fo/+7 YDWBB69TiN+qq0mHmLaTzpD75doZKL+4i1dh3WwtV86Zm5oXU2VNbZPGMqzNtU02O4 l79jooWTgJ43CXl9hQKYZytrHy7yR5/ue9BSOIUQmcBndPEQc22NdLoGP5fcP3fd8k EbZs1Ektv2hhPSua125rdXESfz6XKGdtwr6JQcmqDBLiINb7EOqXTWOc4tsNtoAbIQ O9xtei//0F1Sg== Message-ID: <7e7b7b9f-5909-4bb9-88ea-d3653f26c95d@kernel.org> Date: Mon, 27 Oct 2025 16:04:31 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Cc: chao@kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org Subject: Re: [PATCH v1] f2fs: fix age extent cache insertion skip on counter overflow To: Xiaole He , jaegeuk@kernel.org References: <20251023035416.7943-1-hexiaole1994@126.com> Content-Language: en-US From: Chao Yu In-Reply-To: <20251023035416.7943-1-hexiaole1994@126.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 10/23/25 11:54, Xiaole He wrote: > The age extent cache uses last_blocks (derived from > allocated_data_blocks) to determine data age. However, there's a > conflict between the deletion > marker (last_blocks=0) and legitimate last_blocks=0 cases when > allocated_data_blocks overflows to 0 after reaching ULLONG_MAX. > > In this case, valid extents are incorrectly skipped due to the > "if (!tei->last_blocks)" check in __update_extent_tree_range(). > > This patch fixes the issue by: > 1. Reserving ULLONG_MAX as an invalid/deletion marker > 2. Limiting allocated_data_blocks to range [0, ULLONG_MAX-1] > 3. Using F2FS_EXTENT_AGE_INVALID for deletion scenarios > 4. Adjusting overflow age calculation from ULLONG_MAX to (ULLONG_MAX-1) > > Reproducer (using a patched kernel with allocated_data_blocks > initialized to ULLONG_MAX - 3 for quick testing): > > Step 1: Mount and check initial state > # dd if=/dev/zero of=/tmp/test.img bs=1M count=100 > # mkfs.f2fs -f /tmp/test.img > # mkdir -p /mnt/f2fs_test > # mount -t f2fs -o loop,age_extent_cache /tmp/test.img /mnt/f2fs_test > # cat /sys/kernel/debug/f2fs/status | grep "Block Age" > Allocated Data Blocks: 18446744073709551612 # ULLONG_MAX - 3 > Inner Struct Count: tree: 1(0), node: 0 > > Step 2: Create files and write data to trigger overflow > # touch /mnt/f2fs_test/{1,2,3,4}.txt; sync > # cat /sys/kernel/debug/f2fs/status | grep "Block Age" > Allocated Data Blocks: 18446744073709551613 # ULLONG_MAX - 2 > Inner Struct Count: tree: 5(0), node: 1 > > # dd if=/dev/urandom of=/mnt/f2fs_test/1.txt bs=4K count=1; sync > # cat /sys/kernel/debug/f2fs/status | grep "Block Age" > Allocated Data Blocks: 18446744073709551614 # ULLONG_MAX - 1 > Inner Struct Count: tree: 5(0), node: 2 > > # dd if=/dev/urandom of=/mnt/f2fs_test/2.txt bs=4K count=1; sync > # cat /sys/kernel/debug/f2fs/status | grep "Block Age" > Allocated Data Blocks: 18446744073709551615 # ULLONG_MAX > Inner Struct Count: tree: 5(0), node: 3 > > # dd if=/dev/urandom of=/mnt/f2fs_test/3.txt bs=4K count=1; sync > # cat /sys/kernel/debug/f2fs/status | grep "Block Age" > Allocated Data Blocks: 0 # Counter overflowed! > Inner Struct Count: tree: 5(0), node: 4 > > Step 3: Trigger the bug - next write should create node but gets skipped > # dd if=/dev/urandom of=/mnt/f2fs_test/4.txt bs=4K count=1; sync > # cat /sys/kernel/debug/f2fs/status | grep "Block Age" > Allocated Data Blocks: 1 > Inner Struct Count: tree: 5(0), node: 4 > > Expected: node: 5 (new extent node for 4.txt) > Actual: node: 4 (extent insertion was incorrectly skipped due to > last_blocks = allocated_data_blocks = 0 in __get_new_block_age) > > After this fix, the extent node is correctly inserted and node count > becomes 5 as expected. > Hi Xiaole, Can we add a Fixes line and Cc stable@kernel.org? Thanks, > Signed-off-by: Xiaole He > --- > fs/f2fs/extent_cache.c | 5 +++-- > fs/f2fs/f2fs.h | 6 ++++++ > fs/f2fs/segment.c | 9 +++++++-- > 3 files changed, 16 insertions(+), 4 deletions(-) > > diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c > index 33e09c453c70..0ed84cc065a7 100644 > --- a/fs/f2fs/extent_cache.c > +++ b/fs/f2fs/extent_cache.c > @@ -808,7 +808,7 @@ static void __update_extent_tree_range(struct inode *inode, > } > goto out_read_extent_cache; > update_age_extent_cache: > - if (!tei->last_blocks) > + if (tei->last_blocks == F2FS_EXTENT_AGE_INVALID) > goto out_read_extent_cache; > > __set_extent_info(&ei, fofs, len, 0, false, > @@ -912,7 +912,7 @@ static int __get_new_block_age(struct inode *inode, struct extent_info *ei, > cur_age = cur_blocks - tei.last_blocks; > else > /* allocated_data_blocks overflow */ > - cur_age = ULLONG_MAX - tei.last_blocks + cur_blocks; > + cur_age = (ULLONG_MAX - 1) - tei.last_blocks + cur_blocks; > > if (tei.age) > ei->age = __calculate_block_age(sbi, cur_age, tei.age); > @@ -1114,6 +1114,7 @@ void f2fs_update_age_extent_cache_range(struct dnode_of_data *dn, > struct extent_info ei = { > .fofs = fofs, > .len = len, > + .last_blocks = F2FS_EXTENT_AGE_INVALID, > }; > > if (!__may_extent_tree(dn->inode, EX_BLOCK_AGE)) > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h > index 5b4e9548a231..fa3c676adc30 100644 > --- a/fs/f2fs/f2fs.h > +++ b/fs/f2fs/f2fs.h > @@ -707,6 +707,12 @@ enum extent_type { > NR_EXTENT_CACHES, > }; > > +/* > + * Reserved value to mark invalid age extents, hence valid block range > + * from 0 to ULLONG_MAX-1 > + */ > +#define F2FS_EXTENT_AGE_INVALID ULLONG_MAX > + > struct extent_info { > unsigned int fofs; /* start offset in a file */ > unsigned int len; /* length of the extent */ > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c > index b45eace879d7..a473cd1fb37d 100644 > --- a/fs/f2fs/segment.c > +++ b/fs/f2fs/segment.c > @@ -3863,8 +3863,13 @@ int f2fs_allocate_data_block(struct f2fs_sb_info *sbi, struct folio *folio, > locate_dirty_segment(sbi, GET_SEGNO(sbi, old_blkaddr)); > locate_dirty_segment(sbi, GET_SEGNO(sbi, *new_blkaddr)); > > - if (IS_DATASEG(curseg->seg_type)) > - atomic64_inc(&sbi->allocated_data_blocks); > + if (IS_DATASEG(curseg->seg_type)) { > + unsigned long long new_val; > + > + new_val = atomic64_inc_return(&sbi->allocated_data_blocks); > + if (unlikely(new_val == ULLONG_MAX)) > + atomic64_set(&sbi->allocated_data_blocks, 0); > + } > > up_write(&sit_i->sentry_lock); >