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Re: [Qemu-devel] [Qemu-block] [PATCH] block/gluster: add support for SEE
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [Qemu-block] [PATCH] block/gluster: add support for SEEK_DATA/SEEK_HOLE |
Date: |
Mon, 7 Mar 2016 12:14:34 -0700 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 |
[adding qemu-devel; ALL patches must cc qemu-devel even when sent to
another list]
On 03/07/2016 11:04 AM, Niels de Vos wrote:
> GlusterFS 3.8 contains support for SEEK_DATA and SEEK_HOLE. This makes
> it possible to detect sparse areas in files.
>
> Signed-off-by: Niels de Vos <address@hidden>
>
> --
> Tested by compiling and running "qemu-img map gluster://..." with a
> build of the current master branch of glusterfs. Using a Fedora
> cloud image (in raw format) shows many SEEK procudure calls going back
> and forth over the network. The output of "qemu map" matches the output
> when run against the image on the local filesystem.
> ---
> block/gluster.c | 159
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> configure | 25 +++++++++
> 2 files changed, 184 insertions(+)
>
> diff --git a/block/gluster.c b/block/gluster.c
> index 65077a0..1430010 100644
> --- a/block/gluster.c
> +++ b/block/gluster.c
> @@ -677,6 +677,153 @@ static int qemu_gluster_has_zero_init(BlockDriverState
> *bs)
> return 0;
> }
>
> +#ifdef CONFIG_GLUSTERFS_SEEK_DATA
> +/*
> + * Find allocation range in @bs around offset @start.
> + * May change underlying file descriptor's file offset.
> + * If @start is not in a hole, store @start in @data, and the
> + * beginning of the next hole in @hole, and return 0.
> + * If @start is in a non-trailing hole, store @start in @hole and the
> + * beginning of the next non-hole in @data, and return 0.
> + * If @start is in a trailing hole or beyond EOF, return -ENXIO.
> + * If we can't find out, return a negative errno other than -ENXIO.
> + *
> + * (Shamefully copied from raw-posix.c, only miniscule adaptions.)
> + */
> +static int find_allocation(BlockDriverState *bs, off_t start,
> + off_t *data, off_t *hole)
> +{
> + BDRVGlusterState *s = bs->opaque;
> + off_t offs;
> +
> + /*
> + * SEEK_DATA cases:
> + * D1. offs == start: start is in data
> + * D2. offs > start: start is in a hole, next data at offs
> + * D3. offs < 0, errno = ENXIO: either start is in a trailing hole
> + * or start is beyond EOF
> + * If the latter happens, the file has been truncated behind
> + * our back since we opened it. All bets are off then.
> + * Treating like a trailing hole is simplest.
> + * D4. offs < 0, errno != ENXIO: we learned nothing
> + */
> + offs = glfs_lseek(s->fd, start, SEEK_DATA);
> + if (offs < 0) {
> + return -errno; /* D3 or D4 */
> + }
> + assert(offs >= start);
> +
> + if (offs > start) {
> + /* D2: in hole, next data at offs */
> + *hole = start;
> + *data = offs;
> + return 0;
> + }
> +
> + /* D1: in data, end not yet known */
> +
> + /*
> + * SEEK_HOLE cases:
> + * H1. offs == start: start is in a hole
> + * If this happens here, a hole has been dug behind our back
> + * since the previous lseek().
> + * H2. offs > start: either start is in data, next hole at offs,
> + * or start is in trailing hole, EOF at offs
> + * Linux treats trailing holes like any other hole: offs ==
> + * start. Solaris seeks to EOF instead: offs > start (blech).
> + * If that happens here, a hole has been dug behind our back
> + * since the previous lseek().
> + * H3. offs < 0, errno = ENXIO: start is beyond EOF
> + * If this happens, the file has been truncated behind our
> + * back since we opened it. Treat it like a trailing hole.
> + * H4. offs < 0, errno != ENXIO: we learned nothing
> + * Pretend we know nothing at all, i.e. "forget" about D1.
> + */
> + offs = glfs_lseek(s->fd, start, SEEK_HOLE);
> + if (offs < 0) {
> + return -errno; /* D1 and (H3 or H4) */
> + }
> + assert(offs >= start);
> +
> + if (offs > start) {
> + /*
> + * D1 and H2: either in data, next hole at offs, or it was in
> + * data but is now in a trailing hole. In the latter case,
> + * all bets are off. Treating it as if it there was data all
> + * the way to EOF is safe, so simply do that.
> + */
> + *data = start;
> + *hole = offs;
> + return 0;
> + }
> +
> + /* D1 and H1 */
> + return -EBUSY;
> +}
> +
> +/*
> + * Returns the allocation status of the specified sectors.
> + *
> + * If 'sector_num' is beyond the end of the disk image the return value is 0
> + * and 'pnum' is set to 0.
> + *
> + * 'pnum' is set to the number of sectors (including and immediately
> following
> + * the specified sector) that are known to be in the same
> + * allocated/unallocated state.
> + *
> + * 'nb_sectors' is the max value 'pnum' should be set to. If nb_sectors goes
> + * beyond the end of the disk image it will be clamped.
> + *
> + * (Based on raw_co_get_block_status() from raw-posix.c.)
> + */
> +static int64_t coroutine_fn qemu_gluster_co_get_block_status(
> + BlockDriverState *bs, int64_t sector_num, int nb_sectors, int *pnum)
> +{
> + BDRVGlusterState *s = bs->opaque;
> + off_t start, data = 0, hole = 0;
> + int64_t total_size;
> + int ret = -EINVAL;
> +
> + if (!s->fd) {
> + return ret;
> + }
> +
> + start = sector_num * BDRV_SECTOR_SIZE;
> + total_size = bdrv_getlength(bs);
> + if (total_size < 0) {
> + return total_size;
> + } else if (start >= total_size) {
> + *pnum = 0;
> + return 0;
> + } else if (start + nb_sectors * BDRV_SECTOR_SIZE > total_size) {
> + nb_sectors = DIV_ROUND_UP(total_size - start, BDRV_SECTOR_SIZE);
> + }
> +
> + ret = find_allocation(bs, start, &data, &hole);
> + if (ret == -ENXIO) {
> + /* Trailing hole */
> + *pnum = nb_sectors;
> + ret = BDRV_BLOCK_ZERO;
> + } else if (ret < 0) {
> + /* No info available, so pretend there are no holes */
> + *pnum = nb_sectors;
> + ret = BDRV_BLOCK_DATA;
> + } else if (data == start) {
> + /* On a data extent, compute sectors to the end of the extent,
> + * possibly including a partial sector at EOF. */
> + *pnum = MIN(nb_sectors, DIV_ROUND_UP(hole - start,
> BDRV_SECTOR_SIZE));
> + ret = BDRV_BLOCK_DATA;
> + } else {
> + /* On a hole, compute sectors to the beginning of the next extent.
> */
> + assert(hole == start);
> + *pnum = MIN(nb_sectors, (data - start) / BDRV_SECTOR_SIZE);
> + ret = BDRV_BLOCK_ZERO;
> + }
> + return ret | BDRV_BLOCK_OFFSET_VALID | start;
> +}
> +#endif /* CONFIG_GLUSTERFS_SEEK_DATA */
> +
> +
> static QemuOptsList qemu_gluster_create_opts = {
> .name = "qemu-gluster-create-opts",
> .head = QTAILQ_HEAD_INITIALIZER(qemu_gluster_create_opts.head),
> @@ -719,6 +866,9 @@ static BlockDriver bdrv_gluster = {
> #ifdef CONFIG_GLUSTERFS_ZEROFILL
> .bdrv_co_write_zeroes = qemu_gluster_co_write_zeroes,
> #endif
> +#ifdef CONFIG_GLUSTERFS_SEEK_DATA
> + .bdrv_co_get_block_status = qemu_gluster_co_get_block_status,
> +#endif
> .create_opts = &qemu_gluster_create_opts,
> };
>
> @@ -746,6 +896,9 @@ static BlockDriver bdrv_gluster_tcp = {
> #ifdef CONFIG_GLUSTERFS_ZEROFILL
> .bdrv_co_write_zeroes = qemu_gluster_co_write_zeroes,
> #endif
> +#ifdef CONFIG_GLUSTERFS_SEEK_DATA
> + .bdrv_co_get_block_status = qemu_gluster_co_get_block_status,
> +#endif
> .create_opts = &qemu_gluster_create_opts,
> };
>
> @@ -773,6 +926,9 @@ static BlockDriver bdrv_gluster_unix = {
> #ifdef CONFIG_GLUSTERFS_ZEROFILL
> .bdrv_co_write_zeroes = qemu_gluster_co_write_zeroes,
> #endif
> +#ifdef CONFIG_GLUSTERFS_SEEK_DATA
> + .bdrv_co_get_block_status = qemu_gluster_co_get_block_status,
> +#endif
> .create_opts = &qemu_gluster_create_opts,
> };
>
> @@ -800,6 +956,9 @@ static BlockDriver bdrv_gluster_rdma = {
> #ifdef CONFIG_GLUSTERFS_ZEROFILL
> .bdrv_co_write_zeroes = qemu_gluster_co_write_zeroes,
> #endif
> +#ifdef CONFIG_GLUSTERFS_SEEK_DATA
> + .bdrv_co_get_block_status = qemu_gluster_co_get_block_status,
> +#endif
> .create_opts = &qemu_gluster_create_opts,
> };
>
> diff --git a/configure b/configure
> index 0c0472a..ca3821c 100755
> --- a/configure
> +++ b/configure
> @@ -3351,6 +3351,9 @@ if test "$glusterfs" != "no" ; then
> if $pkg_config --atleast-version=6 glusterfs-api; then
> glusterfs_zerofill="yes"
> fi
> + if $pkg_config --atleast-version=7.3.8 glusterfs-api; then
> + glusterfs_seek_data="yes"
> + fi
> else
> if test "$glusterfs" = "yes" ; then
> feature_not_found "GlusterFS backend support" \
> @@ -3660,6 +3663,24 @@ if compile_prog "" "" ; then
> fiemap=yes
> fi
>
> +# check for SEEK_DATA and SEEK_HOLE
> +seek_data=no
> +cat > $TMPC << EOF
> +#define _GNU_SOURCE
> +#include <sys/types.h>
> +#include <unistd.h>
> +
> +int main(void)
> +{
> + lseek(0, 0, SEEK_DATA);
> + lseek(0, 0, SEEK_HOLE);
> + return 0;
> +}
> +EOF
> +if compile_prog "" "" ; then
> + seek_data=yes
> +fi
> +
> # check for dup3
> dup3=no
> cat > $TMPC << EOF
> @@ -5278,6 +5299,10 @@ if test "$glusterfs_zerofill" = "yes" ; then
> echo "CONFIG_GLUSTERFS_ZEROFILL=y" >> $config_host_mak
> fi
>
> +if test "$glusterfs_seek_data" = "yes" && test "$seek_data" = "yes" ; then
> + echo "CONFIG_GLUSTERFS_SEEK_DATA=y" >> $config_host_mak
> +fi
> +
> if test "$archipelago" = "yes" ; then
> echo "CONFIG_ARCHIPELAGO=m" >> $config_host_mak
> echo "ARCHIPELAGO_LIBS=$archipelago_libs" >> $config_host_mak
>
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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- Re: [Qemu-devel] [Qemu-block] [PATCH] block/gluster: add support for SEEK_DATA/SEEK_HOLE,
Eric Blake <=
- Re: [Qemu-devel] [Qemu-block] [PATCH] block/gluster: add support for SEEK_DATA/SEEK_HOLE, Niels de Vos, 2016/03/07
- Re: [Qemu-devel] [Qemu-block] [PATCH] block/gluster: add support for SEEK_DATA/SEEK_HOLE, Jeff Cody, 2016/03/08
- Re: [Qemu-devel] [Qemu-block] [PATCH] block/gluster: add support for SEEK_DATA/SEEK_HOLE, Niels de Vos, 2016/03/08
- [Qemu-devel] [PATCH v2] block/gluster: add support for SEEK_DATA/SEEK_HOLE, Niels de Vos, 2016/03/09
- Re: [Qemu-devel] [PATCH v2] block/gluster: add support for SEEK_DATA/SEEK_HOLE, Jeff Cody, 2016/03/09
- Re: [Qemu-devel] [PATCH v2] block/gluster: add support for SEEK_DATA/SEEK_HOLE, Niels de Vos, 2016/03/09
- Re: [Qemu-devel] [PATCH v2] block/gluster: add support for SEEK_DATA/SEEK_HOLE, Jeff Cody, 2016/03/09
- [Qemu-devel] [PATCH v3] block/gluster: add support for SEEK_DATA/SEEK_HOLE, Niels de Vos, 2016/03/10
- Re: [Qemu-devel] [PATCH v3] block/gluster: add support for SEEK_DATA/SEEK_HOLE, Jeff Cody, 2016/03/15
- Re: [Qemu-devel] [PATCH v3] block/gluster: add support for SEEK_DATA/SEEK_HOLE, Jeff Cody, 2016/03/15