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Tue, 01 Sep 2026 15:48:03 -0700 (PDT) Message-ID: Date: Wed, 2 Sep 2026 08:17:59 +0930 Precedence: bulk X-Mailing-List: linux-xfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4] iomap: follow the alignment requirement for iomap_dio_hole_iter() From: Qu Wenruo To: linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-xfs@vger.kernel.org, Christian Brauner References: <73bd4d9b39e821453028ca8e567eaad2ebe0fc18.1785880740.git.wqu@suse.com> Content-Language: en-US Autocrypt: addr=wqu@suse.com; keydata= xsBNBFnVga8BCACyhFP3ExcTIuB73jDIBA/vSoYcTyysFQzPvez64TUSCv1SgXEByR7fju3o 8RfaWuHCnkkea5luuTZMqfgTXrun2dqNVYDNOV6RIVrc4YuG20yhC1epnV55fJCThqij0MRL 1NxPKXIlEdHvN0Kov3CtWA+R1iNN0RCeVun7rmOrrjBK573aWC5sgP7YsBOLK79H3tmUtz6b 9Imuj0ZyEsa76Xg9PX9Hn2myKj1hfWGS+5og9Va4hrwQC8ipjXik6NKR5GDV+hOZkktU81G5 gkQtGB9jOAYRs86QG/b7PtIlbd3+pppT0gaS+wvwMs8cuNG+Pu6KO1oC4jgdseFLu7NpABEB AAHNGFF1IFdlbnJ1byA8d3F1QHN1c2UuY29tPsLAlAQTAQgAPgIbAwULCQgHAgYVCAkKCwIE FgIDAQIeAQIXgBYhBC3fcuWlpVuonapC4cI9kfOhJf6oBQJnEXVgBQkQ/lqxAAoJEMI9kfOh Jf6o+jIH/2KhFmyOw4XWAYbnnijuYqb/obGae8HhcJO2KIGcxbsinK+KQFTSZnkFxnbsQ+VY fvtWBHGt8WfHcNmfjdejmy9si2jyy8smQV2jiB60a8iqQXGmsrkuR+AM2V360oEbMF3gVvim 2VSX2IiW9KERuhifjseNV1HLk0SHw5NnXiWh1THTqtvFFY+CwnLN2GqiMaSLF6gATW05/sEd V17MdI1z4+WSk7D57FlLjp50F3ow2WJtXwG8yG8d6S40dytZpH9iFuk12Sbg7lrtQxPPOIEU rpmZLfCNJJoZj603613w/M8EiZw6MohzikTWcFc55RLYJPBWQ+9puZtx1DopW2jOwE0EWdWB rwEIAKpT62HgSzL9zwGe+WIUCMB+nOEjXAfvoUPUwk+YCEDcOdfkkM5FyBoJs8TCEuPXGXBO Cl5P5B8OYYnkHkGWutAVlUTV8KESOIm/KJIA7jJA+Ss9VhMjtePfgWexw+P8itFRSRrrwyUf E+0WcAevblUi45LjWWZgpg3A80tHP0iToOZ5MbdYk7YFBE29cDSleskfV80ZKxFv6koQocq0 vXzTfHvXNDELAuH7Ms/WJcdUzmPyBf3Oq6mKBBH8J6XZc9LjjNZwNbyvsHSrV5bgmu/THX2n g/3be+iqf6OggCiy3I1NSMJ5KtR0q2H2Nx2Vqb1fYPOID8McMV9Ll6rh8S8AEQEAAcLAfAQY AQgAJgIbDBYhBC3fcuWlpVuonapC4cI9kfOhJf6oBQJnEXWBBQkQ/lrSAAoJEMI9kfOhJf6o cakH+QHwDszsoYvmrNq36MFGgvAHRjdlrHRBa4A1V1kzd4kOUokongcrOOgHY9yfglcvZqlJ qfa4l+1oxs1BvCi29psteQTtw+memmcGruKi+YHD7793zNCMtAtYidDmQ2pWaLfqSaryjlzR /3tBWMyvIeWZKURnZbBzWRREB7iWxEbZ014B3gICqZPDRwwitHpH8Om3eZr7ygZck6bBa4MU o1XgbZcspyCGqu1xF/bMAY2iCDcq6ULKQceuKkbeQ8qxvt9hVxJC2W3lHq8dlK1pkHPDg9wO JoAXek8MF37R8gpLoGWl41FIUb3hFiu3zhDDvslYM4BmzI18QgQTQnotJH8= In-Reply-To: <73bd4d9b39e821453028ca8e567eaad2ebe0fc18.1785880740.git.wqu@suse.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Gentle ping? This patch has multiple reviewed-by tags, but I still didn't see it in the upstream rc1 nor vfs.all branch. Thanks, Qu 在 2026/8/5 07:29, Qu Wenruo 写道: > [BUG] > On the latest development branch, btrfs with 8K block size on 4K page > sized systems will fail all test cases that run fsstress. > > One very short example would be: > > # $fsstress -n 4 -d $mnt -s 1785675805 -v > 0/0: dwrite - no filename > 0/1: creat f0 x:0 0 0 > 0/1: creat add id=0,parent=-1 > 0/2: write dontcache f0[259 1 0 0 0 0] [816411,3620] 0 > 0/3: dread - xfsctl(XFS_IOC_DIOINFO) f0[259 1 0 0 32 820031] return 25, fallback to stat() > 0/3: dread f0[259 1 0 0 32 820031] [483328,81920] 0 > > Which triggered the following ASSERT(): > > assertion failed: IS_ALIGNED(state->start, blocksize) && IS_ALIGNED(state->end + 1, blocksize), in fs/btrfs/extent-io-tree.c:346 (unaligned extent state, blocksize=8192 start=487424 end=565247 state=0x0) > ------------[ cut here ]------------ > kernel BUG at fs/btrfs/extent-io-tree.c:346! > Oops: invalid opcode: 0000 [#1] SMP > CPU: 4 UID: 0 PID: 648 Comm: fsstress Tainted: G E 7.2.0-rc5-custom+ #431 PREEMPT(full) 7c507bd40d65e4d871e698b22d80f1306bbec543 > Tainted: [E]=UNSIGNED_MODULE > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS unknown 02/02/2022 > RIP: 0010:validate_extent_state.part.0.isra.0.cold+0x24/0x26 [btrfs] > Call Trace: > > insert_state+0x34/0x1a0 [btrfs 6924944583e4bc91a7c5183a1e7908e745a9b0c8] > set_extent_bit+0x440/0x8d0 [btrfs 6924944583e4bc91a7c5183a1e7908e745a9b0c8] > btrfs_lock_extent_bits+0x58/0x380 [btrfs 6924944583e4bc91a7c5183a1e7908e745a9b0c8] > btrfs_dio_iomap_begin+0x319/0xb70 [btrfs 6924944583e4bc91a7c5183a1e7908e745a9b0c8] > iomap_iter+0x1a2/0x370 > __iomap_dio_rw+0x236/0x8d0 > iomap_dio_rw+0x12/0x30 > btrfs_direct_read+0x15f/0x290 [btrfs 6924944583e4bc91a7c5183a1e7908e745a9b0c8] > btrfs_file_read_iter+0x42/0x90 [btrfs 6924944583e4bc91a7c5183a1e7908e745a9b0c8] > vfs_read+0x25e/0x380 > ksys_read+0x73/0xe0 > do_syscall_64+0xe1/0x790 > entry_SYSCALL_64_after_hwframe+0x4b/0x53 > RIP: 0033:0x7fc3f129318e > > > [CAUSE] > iomap_dio_hole_iter() is responsible for zeroing out the buffer for a > hole, which calls iov_iter_zero() to zero the range. > > However btrfs disables page fault during its __iomap_dio_rw() call, so > iov_iter_zero() can fail at any page boundary. > > When the fs block size is larger than page size, iov_iter_zero() may > only have zeroed one page, which is not aligned to the fs block size. > > Such one page long range is passed back to btrfs, which triggers the > above ASSERT(). > > [FIX] > For iomap_dio_hole_iter() round down the copied length, and revert > any excessive range that is beyond the aligned copied length. > Also use @aligned_copied for the size increment and iter advancement. > > This should only affect btrfs, which is the only fs utilizing iomap dio > with page fault disabled. > > Fixes: 001397f5ef49 ("iomap: add IOMAP_DIO_FSBLOCK_ALIGNED flag") > Signed-off-by: Qu Wenruo > --- > v4: > - Always align down to fs block size > > v3: > - Fix a NULL pointer dereference where @bdev can be NULL for holes > > v2: > - Rebased to the latest vfs tree > > - Slightly rewords the reproducer > In fact no special reproducer needed, any test case running fsstress > can easily trigger it. > > The example provided is just the shortest sequence I used to debug the > crash. > --- > fs/iomap/direct-io.c | 15 +++++++++++---- > 1 file changed, 11 insertions(+), 4 deletions(-) > > diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c > index b3368d64e81b..01f26fb3b3b2 100644 > --- a/fs/iomap/direct-io.c > +++ b/fs/iomap/direct-io.c > @@ -594,12 +594,19 @@ static int iomap_dio_bio_iter(struct iomap_iter *iter, struct iomap_dio *dio) > > static int iomap_dio_hole_iter(struct iomap_iter *iter, struct iomap_dio *dio) > { > - loff_t length = iov_iter_zero(iomap_length(iter), dio->submit.iter); > + loff_t copied = iov_iter_zero(iomap_length(iter), dio->submit.iter); > + unsigned int bs = i_blocksize(iter->inode); > + loff_t aligned_copied = round_down(copied, bs); > > - dio->size += length; > - if (!length) > + /* > + * If fs block size is larger than page size, page fault failure > + * can cause @copied to be page aligned but not fs block aligned. > + */ > + iov_iter_revert(dio->submit.iter, copied - aligned_copied); > + dio->size += aligned_copied; > + if (!aligned_copied) > return -EFAULT; > - return iomap_iter_advance(iter, length); > + return iomap_iter_advance(iter, aligned_copied); > } > > static int iomap_dio_inline_iter(struct iomap_iter *iomi, struct iomap_dio *dio)