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Mon, 24 Nov 2025 02:43:48 -0800 (PST) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Mon, 24 Nov 2025 11:43:46 +0100 To: Benjamin Marzinski Cc: Uladzislau Rezki , Christoph Hellwig , Mikulas Patocka , Alasdair Kergon , DMML , Andrew Morton , Mike Snitzer , LKML Subject: Re: [RESEND PATCH] dm-ebs: Mark full buffer dirty even on partial write Message-ID: References: <73556fc8-5fbf-37cb-26b9-7cdb88f69720@redhat.com> <230baa83-cd79-f232-5fb8-1476115e1ae7@redhat.com> <20251119054635.GB19993@lst.de> <20251120062146.GA29990@lst.de> <20251121072421.GA29754@lst.de> Precedence: bulk X-Mailing-List: dm-devel@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: > On Fri, Nov 21, 2025 at 02:21:34PM +0100, Uladzislau Rezki wrote: > > On Fri, Nov 21, 2025 at 08:24:21AM +0100, Christoph Hellwig wrote: > > > On Thu, Nov 20, 2025 at 01:08:57PM +0100, Uladzislau Rezki wrote: > > > > Could you please check below? Is the last one is correctly reported? > > > > > > The latter looks unexpected, but is is becase qemu is not passing through > > > the qemu physical_block_size attribute to any of the nvme settings Linux > > > interprets as such for NVMe (NVMe doesn't actually have the concept of > > > a physical block size, unlike SCSI/ATA): > > > > > OK, understood and thank you for checking this. > > > > > > > > root@testvm:~# nvme id-ns -H /dev/nvme0n1 | grep npw > > > npwg : 0 > > > npwa : 0 > > > root@testvm:~# nvme id-ns -H /dev/nvme0n1 | grep naw > > > nawun : 0 > > > nawupf : 0 > > > root@testvm:~# nvme id-ctrl -H /dev/nvme0 | grep awupf > > > awupf : 0 > > > > > > but as said multiple times, that should not really matter - the logical > > > block size is the granularity of I/O, the physical block size is just > > > a performance hint. > > > > > Right. > > > > As stated in commit message of the patch which is in question. 8K > > emulated in qemu device with CONFIG_TRANSPARENT_HUGEPAGE=y: > > > > urezki@pc638:~$ sudo nvme list > > Node Generic SN Model Namespace Usage Format FW Rev > > --------------------- --------------------- -------------------- ---------------------------------------- --------- -------------------------- ---------------- -------- > > /dev/nvme0n1 /dev/ng0n1 foo QEMU NVMe Ctrl 1 8.49 GB / 8.49 GB 8 KiB + 0 B 10.0.6 > > urezki@pc638:~$ cat bin/dmsetup.sh > > #!/bin/bash > > > > lower=/dev/nvme0n1 > > len=$(blockdev --getsz "$lower") > > > > echo "0 $len ebs $lower 0 1 16" | dmsetup create nvme-8k > > urezki@pc638:~$ sudo bin/dmsetup.sh > > urezki@pc638:~$ sudo cat /sys/block/nvme0n1/queue/logical_block_size > > 8192 > > urezki@pc638:~$ sudo cat /sys/block/nvme0n1/queue/physical_block_size > > 8192 > > urezki@pc638:~$ sudo cat /sys/block/dm-0/queue/logical_block_size > > 512 > > urezki@pc638:~$ sudo cat /sys/block/dm-0/queue/physical_block_size > > 8192 > > urezki@pc638:~$ sudo mkfs.ext4 -F /dev/dm-0 > > mke2fs 1.47.0 (5-Feb-2023) > > /dev/dm-0 contains a ext4 file system > > last mounted on Fri Nov 21 12:22:55 2025 > > Discarding device blocks: done > > Creating filesystem with 2072576 4k blocks and 518144 inodes > > Filesystem UUID: f71adb05-c020-4406-bc0d-bdb9e5c29af7 > > Superblock backups stored on blocks: > > 32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632 > > > > Allocating group tables: done > > Writing inode tables: done > > Creating journal (16384 blocks): done > > Writing superblocks and filesystem accounting information: mkfs.ext4: Input/output error while writing out and closing file system > > urezki@pc638:~$ sudo dmesg | grep -i "i/o" > > [ 71.813322] Buffer I/O error on dev dm-0, logical block 10, lost async page write > > [ 71.813373] Buffer I/O error on dev dm-0, logical block 11, lost async page write > > [ 71.813395] Buffer I/O error on dev dm-0, logical block 12, lost async page write > > [ 71.813415] Buffer I/O error on dev dm-0, logical block 13, lost async page write > > [ 71.813433] Buffer I/O error on dev dm-0, logical block 14, lost async page write > > [ 71.813451] Buffer I/O error on dev dm-0, logical block 15, lost async page write > > [ 71.813475] Buffer I/O error on dev dm-0, logical block 16, lost async page write > > [ 71.813493] Buffer I/O error on dev dm-0, logical block 17, lost async page write > > [ 71.813516] Buffer I/O error on dev dm-0, logical block 18, lost async page write > > [ 71.813537] Buffer I/O error on dev dm-0, logical block 19, lost async page write > > urezki@pc638:~$ > > > > with the patch: > > > > urezki@pc638:~$ sudo nvme list > > Node Generic SN Model Namespace Usage Format FW Rev > > --------------------- --------------------- -------------------- ---------------------------------------- --------- -------------------------- ---------------- -------- > > /dev/nvme0n1 /dev/ng0n1 foo QEMU NVMe Ctrl 1 8.49 GB / 8.49 GB 8 KiB + 0 B 10.0.6 > > urezki@pc638:~$ cat bin/dmsetup.sh > > #!/bin/bash > > > > lower=/dev/nvme0n1 > > len=$(blockdev --getsz "$lower") > > > > echo "0 $len ebs $lower 0 1 16" | dmsetup create nvme-8k > > urezki@pc638:~$ sudo bin/dmsetup.sh > > urezki@pc638:~$ sudo cat /sys/block/nvme0n1/queue/logical_block_size > > 8192 > > urezki@pc638:~$ sudo cat /sys/block/nvme0n1/queue/physical_block_size > > 8192 > > urezki@pc638:~$ sudo cat /sys/block/dm-0/queue/logical_block_size > > 512 > > urezki@pc638:~$ sudo cat /sys/block/dm-0/queue/physical_block_size > > 8192 > > urezki@pc638:~$ sudo mkfs.ext4 -F /dev/dm-0 > > mke2fs 1.47.0 (5-Feb-2023) > > Discarding device blocks: done > > Creating filesystem with 2072576 4k blocks and 518144 inodes > > Filesystem UUID: c7dff4c7-aa7e-4c94-98ee-f9ea2da92a06 > > Superblock backups stored on blocks: > > 32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632 > > > > Allocating group tables: done > > Writing inode tables: done > > Creating journal (16384 blocks): done > > Writing superblocks and filesystem accounting information: done > > > > urezki@pc638:~$ sudo mount /dev/dm-0 /mnt/ > > urezki@pc638:~$ ls -al /mnt/ > > total 24 > > drwxr-xr-x 3 root root 4096 Nov 21 12:22 . > > drwxr-xr-x 19 root root 4096 Jul 10 19:42 .. > > drwx------ 2 root root 16384 Nov 21 12:22 lost+found > > urezki@pc638:~$ > > > > How do we solve this? > > > > Mikulas proposed to use below patch: > > > > > > Index: linux-2.6/drivers/md/dm-bufio.c > > =================================================================== > > --- linux-2.6.orig/drivers/md/dm-bufio.c 2025-10-13 21:42:47.000000000 +0200 > > +++ linux-2.6/drivers/md/dm-bufio.c 2025-10-20 14:40:32.000000000 +0200 > > @@ -1374,7 +1374,7 @@ static void submit_io(struct dm_buffer * > > { > > unsigned int n_sectors; > > sector_t sector; > > - unsigned int offset, end; > > + unsigned int offset, end, align; > > > > b->end_io = end_io; > > > > @@ -1388,9 +1388,10 @@ static void submit_io(struct dm_buffer * > > b->c->write_callback(b); > > offset = b->write_start; > > end = b->write_end; > > - offset &= -DM_BUFIO_WRITE_ALIGN; > > - end += DM_BUFIO_WRITE_ALIGN - 1; > > - end &= -DM_BUFIO_WRITE_ALIGN; > > + align = max(DM_BUFIO_WRITE_ALIGN, bdev_logical_block_size(b->c->bdev)); > > + offset &= -align; > > + end += align - 1; > > + end &= -align; > > if (unlikely(end > b->c->block_size)) > > end = b->c->block_size; > > > > > > and it fixes the setup which i described in the commit message, but i > > have question. > > > > Why in dm-ebs we need to offload partial buffer < ubf size? > > Um, did you notice that Mikulas accepted your patch? > I saw, he mentioned that and i am glad that during this discussion we came to one more extra patch. I got the feeling that there were misunderstanding between us, so i decided to make it more clear that is it. Thank you. -- Uladzislau Rezki