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block/gluster: add support for SEEK_DATA/SEEK_HOLE

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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 <ndevos@redhat.com>
Reviewed-by: Jeff Cody <jcody@redhat.com>
This commit is contained in:
Niels de Vos 2016-03-10 19:38:00 +01:00 committed by Jeff Cody
parent d7f3040357
commit 947eb2030e
1 changed files with 182 additions and 0 deletions
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182
block/gluster.c
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@ -24,6 +24,7 @@ typedef struct GlusterAIOCB {
typedef struct BDRVGlusterState {
struct glfs *glfs;
struct glfs_fd *fd;
bool supports_seek_data;
} BDRVGlusterState;
typedef struct GlusterConf {
@ -287,6 +288,28 @@ static void qemu_gluster_parse_flags(int bdrv_flags, int *open_flags)
}
}
/*
* Do SEEK_DATA/HOLE to detect if it is functional. Older broken versions of
* gfapi incorrectly return the current offset when SEEK_DATA/HOLE is used.
* - Corrected versions return -1 and set errno to EINVAL.
* - Versions that support SEEK_DATA/HOLE correctly, will return -1 and set
* errno to ENXIO when SEEK_DATA is called with a position of EOF.
*/
static bool qemu_gluster_test_seek(struct glfs_fd *fd)
{
off_t ret, eof;
eof = glfs_lseek(fd, 0, SEEK_END);
if (eof < 0) {
/* this should never occur */
return false;
}
/* this should always fail with ENXIO if SEEK_DATA is supported */
ret = glfs_lseek(fd, eof, SEEK_DATA);
return (ret < 0) && (errno == ENXIO);
}
static int qemu_gluster_open(BlockDriverState *bs, QDict *options,
int bdrv_flags, Error **errp)
{
@ -338,6 +361,8 @@ static int qemu_gluster_open(BlockDriverState *bs, QDict *options,
ret = -errno;
}
s->supports_seek_data = qemu_gluster_test_seek(s->fd);
out:
qemu_opts_del(opts);
qemu_gluster_gconf_free(gconf);
@ -727,6 +752,159 @@ static int qemu_gluster_has_zero_init(BlockDriverState *bs)
return 0;
}
/*
* 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;
if (!s->supports_seek_data) {
return -ENOTSUP;
}
/*
* 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,
BlockDriverState **file)
{
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;
}
*file = bs;
return ret | BDRV_BLOCK_OFFSET_VALID | start;
}
static QemuOptsList qemu_gluster_create_opts = {
.name = "qemu-gluster-create-opts",
.head = QTAILQ_HEAD_INITIALIZER(qemu_gluster_create_opts.head),
@ -769,6 +947,7 @@ static BlockDriver bdrv_gluster = {
#ifdef CONFIG_GLUSTERFS_ZEROFILL
.bdrv_co_pwrite_zeroes = qemu_gluster_co_pwrite_zeroes,
#endif
.bdrv_co_get_block_status = qemu_gluster_co_get_block_status,
.create_opts = &qemu_gluster_create_opts,
};
@ -796,6 +975,7 @@ static BlockDriver bdrv_gluster_tcp = {
#ifdef CONFIG_GLUSTERFS_ZEROFILL
.bdrv_co_pwrite_zeroes = qemu_gluster_co_pwrite_zeroes,
#endif
.bdrv_co_get_block_status = qemu_gluster_co_get_block_status,
.create_opts = &qemu_gluster_create_opts,
};
@ -823,6 +1003,7 @@ static BlockDriver bdrv_gluster_unix = {
#ifdef CONFIG_GLUSTERFS_ZEROFILL
.bdrv_co_pwrite_zeroes = qemu_gluster_co_pwrite_zeroes,
#endif
.bdrv_co_get_block_status = qemu_gluster_co_get_block_status,
.create_opts = &qemu_gluster_create_opts,
};
@ -850,6 +1031,7 @@ static BlockDriver bdrv_gluster_rdma = {
#ifdef CONFIG_GLUSTERFS_ZEROFILL
.bdrv_co_pwrite_zeroes = qemu_gluster_co_pwrite_zeroes,
#endif
.bdrv_co_get_block_status = qemu_gluster_co_get_block_status,
.create_opts = &qemu_gluster_create_opts,
};