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Date: Tue, 17 Nov 2020 18:30:11 +0300
From: Благодаренко Артём
<artem.blagodarenko@...il.com>
To: linux-ext4@...r.kernel.org
Cc: adilger.kernel@...ger.ca,
Alexey Lyashkov <alexey.lyashkov@....com>,
Theodore Tso <tytso@...gle.com>
Subject: Re: [PATCH] libfs: Fix DIO mode aligment
Hello,
Any thoughts about this change? Thanks.
Best regards,
Artem Blagodarenko.
> On 23 Oct 2020, at 14:26, Artem Blagodarenko <artem.blagodarenko@...il.com> wrote:
>
> From: Alexey Lyashkov <alexey.lyashkov@....com>
>
> Bounce buffer must be extended to hold a whole disk block size.
> Read/write operations with unaligned offsets is prohobined
> in the DIO mode, so read/write blocks should be adjusted to
> reflect it.
>
> Change-Id: Ic573c9ff0d476028dd2293f8b814c6112705db0e
> Signed-off-by: Alexey Lyashkov <alexey.lyashkov@....com>
> HPE-bug-id: LUS-9241
> ---
> lib/ext2fs/io_manager.c | 5 +-
> lib/ext2fs/unix_io.c | 296 +++++++++++++++++++++++++---------------
> 2 files changed, 190 insertions(+), 111 deletions(-)
>
> diff --git a/lib/ext2fs/io_manager.c b/lib/ext2fs/io_manager.c
> index c395d615..84399a12 100644
> --- a/lib/ext2fs/io_manager.c
> +++ b/lib/ext2fs/io_manager.c
> @@ -20,6 +20,9 @@
> #include "ext2_fs.h"
> #include "ext2fs.h"
>
> +#define max(a, b) ((a) > (b) ? (a) : (b))
> +
> +
> errcode_t io_channel_set_options(io_channel channel, const char *opts)
> {
> errcode_t retval = 0;
> @@ -128,7 +131,7 @@ errcode_t io_channel_alloc_buf(io_channel io, int count, void *ptr)
> size_t size;
>
> if (count == 0)
> - size = io->block_size;
> + size = max(io->block_size, io->align);
> else if (count > 0)
> size = io->block_size * count;
> else
> diff --git a/lib/ext2fs/unix_io.c b/lib/ext2fs/unix_io.c
> index 628e60c3..53647a22 100644
> --- a/lib/ext2fs/unix_io.c
> +++ b/lib/ext2fs/unix_io.c
> @@ -154,46 +154,30 @@ static char *safe_getenv(const char *arg)
> /*
> * Here are the raw I/O functions
> */
> -static errcode_t raw_read_blk(io_channel channel,
> +static errcode_t raw_aligned_read_blk(io_channel channel,
> struct unix_private_data *data,
> - unsigned long long block,
> - int count, void *bufv)
> + ext2_loff_t location,
> + ssize_t size, void *bufv,
> + int *asize)
> {
> - errcode_t retval;
> - ssize_t size;
> - ext2_loff_t location;
> int actual = 0;
> + errcode_t retval;
> unsigned char *buf = bufv;
> - ssize_t really_read = 0;
> -
> - size = (count < 0) ? -count : (ext2_loff_t) count * channel->block_size;
> - data->io_stats.bytes_read += size;
> - 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) {
> - retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
> - goto error_out;
> - }
> - goto bounce_read;
> - }
> +#ifdef ALIGN_DEBUG
> + printf("raw_aligned_read_blk: %p %lu<>%lu\n", buf,
> + location, (unsigned long) size);
> +#endif
>
> #ifdef HAVE_PREAD64
> /* Try an aligned pread */
> - if ((channel->align == 0) ||
> - (IS_ALIGNED(buf, channel->align) &&
> - IS_ALIGNED(size, channel->align))) {
> - actual = pread64(data->dev, buf, size, location);
> - if (actual == size)
> - return 0;
> - actual = 0;
> - }
> + actual = pread64(data->dev, buf, size, location);
> + if (actual == size)
> + return 0;
> + actual = 0;
> #elif HAVE_PREAD
> /* Try an aligned pread */
> - if ((sizeof(off_t) >= sizeof(ext2_loff_t)) &&
> - ((channel->align == 0) ||
> - (IS_ALIGNED(buf, channel->align) &&
> - IS_ALIGNED(size, channel->align)))) {
> + if (sizeof(off_t) >= sizeof(ext2_loff_t)) {
> actual = pread(data->dev, buf, size, location);
> if (actual == size)
> return 0;
> @@ -205,47 +189,100 @@ static errcode_t raw_read_blk(io_channel channel,
> retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
> goto error_out;
> }
> +
> + actual = read(data->dev, buf, size);
> + if (actual != size) {
> + if (actual < 0) {
> + retval = errno;
> + actual = 0;
> + } else {
> + retval = EXT2_ET_SHORT_READ;
> + }
> + }
> +
> +error_out:
> + *asize = actual;
> + return retval;
> +}
> +
> +
> +/*
> + * Here are the raw I/O functions
> + */
> +static errcode_t raw_read_blk(io_channel channel,
> + struct unix_private_data *data,
> + unsigned long long block,
> + int count, void *bufv)
> +{
> + errcode_t retval;
> + ssize_t size;
> + ext2_loff_t location;
> + int actual = 0;
> + unsigned char *buf = bufv;
> + unsigned int align = channel->align;
> + ssize_t really_read = 0;
> + blk64_t blk;
> + loff_t offset;
> +
> + size = (count < 0) ? -count : count * channel->block_size;
> + data->io_stats.bytes_read += size;
> + location = ((ext2_loff_t) block * channel->block_size) + data->offset;
> +
> + if (data->flags & IO_FLAG_FORCE_BOUNCE) {
> + align = channel->block_size;
> + goto bounce_read;
> + }
> +
> if ((channel->align == 0) ||
> - (IS_ALIGNED(buf, channel->align) &&
> + (IS_ALIGNED(location, channel->align) &&
> + IS_ALIGNED(buf, channel->align) &&
> IS_ALIGNED(size, channel->align))) {
> - actual = read(data->dev, buf, size);
> - if (actual != size) {
> - short_read:
> - if (actual < 0) {
> - retval = errno;
> - actual = 0;
> - } else
> - retval = EXT2_ET_SHORT_READ;
> + retval = raw_aligned_read_blk(channel, data, location,
> + size, bufv, &actual);
> + if (retval != 0)
> goto error_out;
> - }
> - return 0;
> +
> + return retval;
> }
>
> +bounce_read:
> #ifdef ALIGN_DEBUG
> - printf("raw_read_blk: O_DIRECT fallback: %p %lu\n", buf,
> - (unsigned long) size);
> + printf("raw_read_blk: O_DIRECT fallback: %p %lu<>%lu\n", buf,
> + location, (unsigned long) size);
> #endif
> -
> /*
> * The buffer or size which we're trying to read isn't aligned
> * to the O_DIRECT rules, so we need to do this the hard way...
> + * read / write must be aligned to the block device sector size
> */
> -bounce_read:
> +
> + blk = location / align;
> + offset = location % align;
> +
> + if (lseek(data->dev, blk * align, SEEK_SET) < 0)
> + return errno;
> +
> while (size > 0) {
> - actual = read(data->dev, data->bounce, channel->block_size);
> - if (actual != channel->block_size) {
> + actual = read(data->dev, data->bounce, align);
> + if (actual != align) {
> actual = really_read;
> buf -= really_read;
> size += really_read;
> - goto short_read;
> + retval = EXT2_ET_SHORT_READ;
> + goto error_out;
> }
> actual = size;
> - if (size > channel->block_size)
> - actual = channel->block_size;
> - memcpy(buf, data->bounce, actual);
> + if ((actual + offset) > align)
> + actual = align - offset;
> + if (actual > size)
> + actual = size;
> +
> + memcpy(buf, data->bounce + offset, actual);
> really_read += actual;
> size -= actual;
> buf += actual;
> + offset = 0;
> + blk++;
> }
> return 0;
>
> @@ -258,6 +295,58 @@ error_out:
> return retval;
> }
>
> +static errcode_t raw_aligned_write_blk(io_channel channel,
> + struct unix_private_data *data,
> + ext2_loff_t location,
> + ssize_t size, const void *bufv,
> + int *asize)
> +
> +{
> + int actual = 0;
> + errcode_t retval;
> + const unsigned char *buf = (void *)bufv;
> +
> +#ifdef ALIGN_DEBUG
> + printf("raw_aligned_write_blk: %p %lu %lu\n", buf,
> + location, (unsigned long) size);
> +#endif
> +
> +#ifdef HAVE_PWRITE64
> + /* Try an aligned pwrite */
> + actual = pwrite64(data->dev, buf, size, location);
> + if (actual == size)
> + return 0;
> +#elif HAVE_PWRITE
> + /* Try an aligned pwrite */
> + if ((sizeof(off_t) >= sizeof(ext2_loff_t)) {
> + actual = pwrite(data->dev, buf, size, location);
> + if (actual == size)
> + return 0;
> + }
> +#endif /* HAVE_PWRITE */
> +
> + if (ext2fs_llseek(data->dev, location, SEEK_SET) != location) {
> + retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
> + goto error_out;
> + }
> +
> + actual = write(data->dev, buf, size);
> + if (actual < 0) {
> + retval = errno;
> + goto error_out;
> + }
> + if (actual != size) {
> + retval = EXT2_ET_SHORT_WRITE;
> + goto error_out;
> + }
> + retval = 0;
> +error_out:
> + *asize = actual;
> + return retval;
> +
> +}
> +
> +
> static errcode_t raw_write_blk(io_channel channel,
> struct unix_private_data *data,
> unsigned long long block,
> @@ -268,6 +357,9 @@ static errcode_t raw_write_blk(io_channel channel,
> int actual = 0;
> errcode_t retval;
> const unsigned char *buf = bufv;
> + unsigned int align = channel->align;
> + blk64_t blk;
> + loff_t offset;
>
> if (count == 1)
> size = channel->block_size;
> @@ -282,95 +374,79 @@ 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) {
> - retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
> - goto error_out;
> - }
> + align = channel->block_size;
> goto bounce_write;
> }
>
> -#ifdef HAVE_PWRITE64
> - /* Try an aligned pwrite */
> if ((channel->align == 0) ||
> - (IS_ALIGNED(buf, channel->align) &&
> + (IS_ALIGNED(location, channel->align) &&
> + IS_ALIGNED(buf, channel->align) &&
> IS_ALIGNED(size, channel->align))) {
> - actual = pwrite64(data->dev, buf, size, location);
> - if (actual == size)
> - return 0;
> - }
> -#elif HAVE_PWRITE
> - /* Try an aligned pwrite */
> - if ((sizeof(off_t) >= sizeof(ext2_loff_t)) &&
> - ((channel->align == 0) ||
> - (IS_ALIGNED(buf, channel->align) &&
> - IS_ALIGNED(size, channel->align)))) {
> - actual = pwrite(data->dev, buf, size, location);
> - if (actual == size)
> - return 0;
> - }
> -#endif /* HAVE_PWRITE */
> + retval = raw_aligned_write_blk(channel, data, location,
> + size, bufv, &actual);
> + if (retval != 0)
> + goto error_out;
>
> - if (ext2fs_llseek(data->dev, location, SEEK_SET) != location) {
> - retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
> - goto error_out;
> + return retval;
> }
>
> - if ((channel->align == 0) ||
> - (IS_ALIGNED(buf, channel->align) &&
> - IS_ALIGNED(size, channel->align))) {
> - actual = write(data->dev, buf, size);
> - if (actual < 0) {
> - retval = errno;
> - goto error_out;
> - }
> - if (actual != size) {
> - short_write:
> - retval = EXT2_ET_SHORT_WRITE;
> - goto error_out;
> - }
> - return 0;
> - }
>
> +bounce_write:
> #ifdef ALIGN_DEBUG
> printf("raw_write_blk: O_DIRECT fallback: %p %lu\n", buf,
> (unsigned long) size);
> #endif
> +
> + /* logical offset may don't aligned with block device block size */
> + blk = location / align;
> + offset = location % align;
> +
> + if (lseek(data->dev, blk * align, SEEK_SET) != blk * align) {
> + retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
> + goto error_out;
> + }
> +
> /*
> * The buffer or size which we're trying to write isn't aligned
> * to the O_DIRECT rules, so we need to do this the hard way...
> */
> -bounce_write:
> while (size > 0) {
> - if (size < channel->block_size) {
> - actual = read(data->dev, data->bounce,
> - channel->block_size);
> - if (actual != channel->block_size) {
> - if (actual < 0) {
> - retval = errno;
> - goto error_out;
> - }
> - memset((char *) data->bounce + actual, 0,
> - channel->block_size - actual);
> + int actual_w;
> +
> + memset((char *) data->bounce, 0, align);
> + if (offset || (size < align)) {
> + actual = read(data->dev, data->bounce, align);
> + if (actual < 0) {
> + retval = errno;
> + goto error_out;
> }
> }
> 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)
> + actual = align - offset;
> + if (actual > size)
> + actual = size;
> + memcpy(((char *)data->bounce) + offset, buf, actual);
> +
> + if (lseek(data->dev, blk * align, SEEK_SET) != blk * align) {
> retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
> goto error_out;
> }
> - actual = write(data->dev, data->bounce, channel->block_size);
> - if (actual < 0) {
> +
> + actual_w = write(data->dev, data->bounce, align);
> + if (actual_w < 0) {
> retval = errno;
> goto error_out;
> }
> - if (actual != channel->block_size)
> - goto short_write;
> + if (actual_w != align) {
> + retval = EXT2_ET_SHORT_WRITE;
> + goto error_out;
> + }
> size -= actual;
> buf += actual;
> location += actual;
> + blk ++;
> + offset = 0;
> }
> return 0;
>
> --
> 2.18.4
>
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