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Date: Mon, 1 Mar 2021 19:14:00 +0300
From: Благодаренко Артём
<artem.blagodarenko@...il.com>
To: Theodore Ts'o <tytso@....edu>
Cc: linux-ext4@...r.kernel.org, adilger.kernel@...ger.ca,
Alexey Lyashkov <alexey.lyashkov@....com>
Subject: Re: [PATCH] libfs: Fix DIO mode aligment
Hello Ted!
Thank you very much for the new version of the fix.
The problem can be easily reproduced, using loop device.
Here is how I reproduced it originally (without the patch)
# truncate -s 512MB /tmp/lustre-ost
# losetup -b 4096 /dev/loop0 /tmp/lustre-ost
# mkfs.ext4 /dev/loop0
mke2fs 1.45.6.wc1 (20-Mar-2020)
detected raid stride 4096 too large, use optimum 512
Discarding device blocks: done
Creating filesystem with 125000 4k blocks and 125056 inodes
Filesystem UUID: 541ad524-556a-45be-84fe-5b68c1ca4562
Superblock backups stored on blocks:
32768, 98304
Allocating group tables: done
Writing inode tables: done
Creating journal (4096 blocks): done
Writing superblocks and filesystem accounting information: done
# git rev-parse HEAD
0f880f553dfa09dabe4cb03752b97a07b66eb998
[root@...2 e2fsprogs-hpe]# misc/e2image /dev/loop0 /tmp/ost-image
e2image 1.45.2.cr2 (09-Apr-2020)
misc/e2image: Attempt to read block from filesystem resulted in short read while trying to open /dev/loop0
Couldn't find valid filesystem superblock.
With your patch e2image works fine.
[root@...2 e2fsprogs-kernel]# truncate -s 512MB /tmp/lustre-ost
[root@...2 e2fsprogs-kernel]# losetup -b 4096 /dev/loop0 /tmp/lustre-ost
[root@...2 e2fsprogs-kernel]# mkfs.ext4 /dev/loop0
mke2fs 1.45.6.wc1 (20-Mar-2020)
detected raid stride 4096 too large, use optimum 512
Discarding device blocks: done
Creating filesystem with 125000 4k blocks and 125056 inodes
Filesystem UUID: 42f6fc7d-382a-4681-99b8-79f3fcd2b4bf
Superblock backups stored on blocks:
32768, 98304
Allocating group tables: done
Writing inode tables: done
Creating journal (4096 blocks): done
Writing superblocks and filesystem accounting information: done
[root@...2 e2fsprogs-kernel]# git rev-parse HEAD
67f2b54667e65cf5a478fcea8b85722be9ee6e8d
[root@...2 e2fsprogs-kernel]# misc/e2image /dev/loop0 /tmp/ost-image
e2image 1.46.1 (9-Feb-2021)
Thanks again.
Best regards,
Artem Blagodarenko.
> On 27 Feb 2021, at 02:17, Theodore Ts'o <tytso@....edu> wrote:
>
> I've rewritten the patch because it was simplest way to review the
> code. The resulting code is simpler and has a smaller number of lines
> of code. I don't have any 4k advanced format disks handy, so I'd
> appreciate it if someone can test it. It passes the existing
> regression tests, and I've run a number of manual tests to simulate a
> advanced format HDD, with the tests being run with clang and UBSAN and
> ADDRSAN enabled.
>
> If someone with access to an advanced format disk can test running
> debugfs -D on an advanced format disk, that would be great, thanks.
>
> - Ted
>
> commit c001596110e834a85b01a47a20811b318cb3b9e4
> Author: Theodore Ts'o <tytso@....edu>
> Date: Fri Feb 26 17:41:06 2021 -0500
>
> libext2fs: fix unix_io's Direct I/O support
>
> The previous Direct I/O support worked on HDD's with 512 byte logical
> sector sizes, and on FreeBSD which required 4k aligned memory buffers.
> However, it was incomplete and was not correctly working on HDD's with
> 4k logical sector sizes (aka Advanced Format Disks).
>
> Based on a patch from Alexey Lyashkov <alexey.lyashkov@....com> but
> rewritten to work with the latest e2fsprogs and to minimize changes to
> make it easier to review.
>
> Signed-off-by: Theodore Ts'o <tytso@....edu>
> Reported-by: Artem Blagodarenko <artem.blagodarenko@...il.com>
>
> diff --git a/lib/ext2fs/io_manager.c b/lib/ext2fs/io_manager.c
> index c395d615..996c31a1 100644
> --- a/lib/ext2fs/io_manager.c
> +++ b/lib/ext2fs/io_manager.c
> @@ -134,9 +134,11 @@ errcode_t io_channel_alloc_buf(io_channel io, int count, void *ptr)
> else
> size = -count;
>
> - if (io->align)
> + if (io->align) {
> + if (io->align > size)
> + size = io->align;
> return ext2fs_get_memalign(size, io->align, ptr);
> - else
> + } else
> return ext2fs_get_mem(size, ptr);
> }
>
> diff --git a/lib/ext2fs/unix_io.c b/lib/ext2fs/unix_io.c
> index 73f5667e..8965535c 100644
> --- a/lib/ext2fs/unix_io.c
> +++ b/lib/ext2fs/unix_io.c
> @@ -218,6 +218,8 @@ static errcode_t raw_read_blk(io_channel channel,
> int actual = 0;
> unsigned char *buf = bufv;
> ssize_t really_read = 0;
> + unsigned long long aligned_blk;
> + int align_size, offset;
>
> size = (count < 0) ? -count : (ext2_loff_t) count * channel->block_size;
> mutex_lock(data, STATS_MTX);
> @@ -226,7 +228,7 @@ static errcode_t raw_read_blk(io_channel channel,
> location = ((ext2_loff_t) block * channel->block_size) + data->offset;
>
> if (data->flags & IO_FLAG_FORCE_BOUNCE) {
> - if (ext2fs_llseek(data->dev, location, SEEK_SET) != location) {
> + if (ext2fs_llseek(data->dev, location, SEEK_SET) < 0) {
> retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
> goto error_out;
> }
> @@ -237,6 +239,7 @@ static errcode_t raw_read_blk(io_channel channel,
> /* Try an aligned pread */
> if ((channel->align == 0) ||
> (IS_ALIGNED(buf, channel->align) &&
> + IS_ALIGNED(location, channel->align) &&
> IS_ALIGNED(size, channel->align))) {
> actual = pread64(data->dev, buf, size, location);
> if (actual == size)
> @@ -248,6 +251,7 @@ static errcode_t raw_read_blk(io_channel channel,
> if ((sizeof(off_t) >= sizeof(ext2_loff_t)) &&
> ((channel->align == 0) ||
> (IS_ALIGNED(buf, channel->align) &&
> + IS_ALIGNED(location, channel->align) &&
> IS_ALIGNED(size, channel->align)))) {
> actual = pread(data->dev, buf, size, location);
> if (actual == size)
> @@ -256,12 +260,13 @@ static errcode_t raw_read_blk(io_channel channel,
> }
> #endif /* HAVE_PREAD */
>
> - if (ext2fs_llseek(data->dev, location, SEEK_SET) != location) {
> + if (ext2fs_llseek(data->dev, location, SEEK_SET) < 0) {
> retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
> goto error_out;
> }
> if ((channel->align == 0) ||
> (IS_ALIGNED(buf, channel->align) &&
> + IS_ALIGNED(location, channel->align) &&
> IS_ALIGNED(size, channel->align))) {
> actual = read(data->dev, buf, size);
> if (actual != size) {
> @@ -286,23 +291,39 @@ static errcode_t raw_read_blk(io_channel channel,
> * to the O_DIRECT rules, so we need to do this the hard way...
> */
> bounce_read:
> + if ((channel->block_size > channel->align) &&
> + (channel->block_size % channel->align) == 0)
> + align_size = channel->block_size;
> + else
> + align_size = channel->align;
> + aligned_blk = location / align_size;
> + offset = location % align_size;
> +
> + if (ext2fs_llseek(data->dev, aligned_blk * align_size, SEEK_SET) < 0) {
> + retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
> + goto error_out;
> + }
> while (size > 0) {
> mutex_lock(data, BOUNCE_MTX);
> - actual = read(data->dev, data->bounce, channel->block_size);
> - if (actual != channel->block_size) {
> + actual = read(data->dev, data->bounce, align_size);
> + if (actual != align_size) {
> mutex_unlock(data, BOUNCE_MTX);
> actual = really_read;
> buf -= really_read;
> size += really_read;
> goto short_read;
> }
> - actual = size;
> - if (size > channel->block_size)
> - actual = channel->block_size;
> - memcpy(buf, data->bounce, actual);
> + if ((actual + offset) > align_size)
> + actual = align_size - offset;
> + if (actual > size)
> + actual = size;
> + memcpy(buf, data->bounce + offset, actual);
> +
> really_read += actual;
> size -= actual;
> buf += actual;
> + offset = 0;
> + aligned_blk++;
> mutex_unlock(data, BOUNCE_MTX);
> }
> return 0;
> @@ -326,6 +347,8 @@ static errcode_t raw_write_blk(io_channel channel,
> int actual = 0;
> errcode_t retval;
> const unsigned char *buf = bufv;
> + unsigned long long aligned_blk;
> + int align_size, offset;
>
> if (count == 1)
> size = channel->block_size;
> @@ -342,7 +365,7 @@ static errcode_t raw_write_blk(io_channel channel,
> location = ((ext2_loff_t) block * channel->block_size) + data->offset;
>
> if (data->flags & IO_FLAG_FORCE_BOUNCE) {
> - if (ext2fs_llseek(data->dev, location, SEEK_SET) != location) {
> + if (ext2fs_llseek(data->dev, location, SEEK_SET) < 0) {
> retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
> goto error_out;
> }
> @@ -353,6 +376,7 @@ static errcode_t raw_write_blk(io_channel channel,
> /* Try an aligned pwrite */
> if ((channel->align == 0) ||
> (IS_ALIGNED(buf, channel->align) &&
> + IS_ALIGNED(location, channel->align) &&
> IS_ALIGNED(size, channel->align))) {
> actual = pwrite64(data->dev, buf, size, location);
> if (actual == size)
> @@ -363,6 +387,7 @@ static errcode_t raw_write_blk(io_channel channel,
> if ((sizeof(off_t) >= sizeof(ext2_loff_t)) &&
> ((channel->align == 0) ||
> (IS_ALIGNED(buf, channel->align) &&
> + IS_ALIGNED(location, channel->align) &&
> IS_ALIGNED(size, channel->align)))) {
> actual = pwrite(data->dev, buf, size, location);
> if (actual == size)
> @@ -370,13 +395,14 @@ static errcode_t raw_write_blk(io_channel channel,
> }
> #endif /* HAVE_PWRITE */
>
> - if (ext2fs_llseek(data->dev, location, SEEK_SET) != location) {
> + if (ext2fs_llseek(data->dev, location, SEEK_SET) < 0) {
> retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
> goto error_out;
> }
>
> if ((channel->align == 0) ||
> (IS_ALIGNED(buf, channel->align) &&
> + IS_ALIGNED(location, channel->align) &&
> IS_ALIGNED(size, channel->align))) {
> actual = write(data->dev, buf, size);
> if (actual < 0) {
> @@ -400,40 +426,59 @@ static errcode_t raw_write_blk(io_channel channel,
> * to the O_DIRECT rules, so we need to do this the hard way...
> */
> bounce_write:
> + if ((channel->block_size > channel->align) &&
> + (channel->block_size % channel->align) == 0)
> + align_size = channel->block_size;
> + else
> + align_size = channel->align;
> + aligned_blk = location / align_size;
> + offset = location % align_size;
> +
> while (size > 0) {
> + int actual_w;
> +
> mutex_lock(data, BOUNCE_MTX);
> - if (size < channel->block_size) {
> + if (size < align_size || offset) {
> + if (ext2fs_llseek(data->dev, aligned_blk * align_size,
> + SEEK_SET) < 0) {
> + retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
> + goto error_out;
> + }
> actual = read(data->dev, data->bounce,
> - channel->block_size);
> - if (actual != channel->block_size) {
> + align_size);
> + if (actual != align_size) {
> if (actual < 0) {
> mutex_unlock(data, BOUNCE_MTX);
> retval = errno;
> goto error_out;
> }
> memset((char *) data->bounce + actual, 0,
> - channel->block_size - actual);
> + align_size - actual);
> }
> }
> actual = size;
> - if (size > channel->block_size)
> - actual = channel->block_size;
> - memcpy(data->bounce, buf, actual);
> - if (ext2fs_llseek(data->dev, location, SEEK_SET) != location) {
> + if ((actual + offset) > align_size)
> + actual = align_size - offset;
> + if (actual > size)
> + actual = size;
> + memcpy(((char *)data->bounce) + offset, buf, actual);
> + if (ext2fs_llseek(data->dev, aligned_blk * align_size, SEEK_SET) < 0) {
> retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
> goto error_out;
> }
> - actual = write(data->dev, data->bounce, channel->block_size);
> + actual_w = write(data->dev, data->bounce, align_size);
> mutex_unlock(data, BOUNCE_MTX);
> - if (actual < 0) {
> + if (actual_w < 0) {
> retval = errno;
> goto error_out;
> }
> - if (actual != channel->block_size)
> + if (actual_w != align_size)
> goto short_write;
> size -= actual;
> buf += actual;
> location += actual;
> + aligned_blk++;
> + offset = 0;
> }
> return 0;
>
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