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block/raw-posix: Try both FIEMAP and SEEK_HOLE

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The current version of raw-posix always uses ioctl(FS_IOC_FIEMAP) if
FIEMAP is available; lseek with SEEK_HOLE/SEEK_DATA are not even
compiled in in this case. However, there may be implementations which
support the latter but not the former (e.g., NFSv4.2) as well as vice
versa.

To cover both cases, try FIEMAP first (as this will return -ENOTSUP if
not supported instead of returning a failsafe value (everything
allocated as a single extent)) and if that does not work, fall back to
SEEK_HOLE/SEEK_DATA.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
(cherry picked from commit 4f11aa8a40)
[BR: BNC#908381]
Signed-off-by: Bruce Rogers <brogers@suse.com>

Conflicts:
	block/raw-posix.c
This commit is contained in:
Max Reitz
2014-05-08 20:57:55 +02:00
committed by Bruce Rogers
parent 215b18c9fc
commit b42aedacc9
1 changed files with 84 additions and 58 deletions
Download Patch File Download Diff File Expand all files Collapse all files

142
block/raw-posix.c
View File

@@ -142,6 +142,9 @@ typedef struct BDRVRawState {
bool is_xfs : 1;
#endif
bool has_discard : 1;
#ifdef CONFIG_FIEMAP
bool skip_fiemap;
#endif
} BDRVRawState;
typedef struct BDRVRawReopenState {
@@ -1035,6 +1038,79 @@ static int raw_create(const char *filename, QEMUOptionParameter *options)
return result;
}
static int try_fiemap(BlockDriverState *bs, off_t start, off_t *data,
off_t *hole, int nb_sectors, int *pnum)
{
#ifdef CONFIG_FIEMAP
BDRVRawState *s = bs->opaque;
struct {
struct fiemap fm;
struct fiemap_extent fe;
} f;
if (s->skip_fiemap) {
return 1;
}
f.fm.fm_start = start;
f.fm.fm_length = (int64_t)nb_sectors * BDRV_SECTOR_SIZE;
f.fm.fm_flags = 0;
f.fm.fm_extent_count = 1;
f.fm.fm_reserved = 0;
if (ioctl(s->fd, FS_IOC_FIEMAP, &f) == -1) {
/* Assume everything is allocated. */
s->skip_fiemap = true;
return 1;
}
if (f.fm.fm_mapped_extents == 0) {
/* No extents found, data is beyond f.fm.fm_start + f.fm.fm_length.
* f.fm.fm_start + f.fm.fm_length must be clamped to the file size!
*/
off_t length = lseek(s->fd, 0, SEEK_END);
*hole = f.fm.fm_start;
*data = MIN(f.fm.fm_start + f.fm.fm_length, length);
} else {
*data = f.fe.fe_logical;
*hole = f.fe.fe_logical + f.fe.fe_length;
}
return 0;
#else
return 1;
#endif
}
static int64_t try_seek_hole(BlockDriverState *bs, off_t start, off_t *data,
off_t *hole, int *pnum)
{
#if defined SEEK_HOLE && defined SEEK_DATA
BDRVRawState *s = bs->opaque;
*hole = lseek(s->fd, start, SEEK_HOLE);
if (*hole == -1) {
/* -ENXIO indicates that sector_num was past the end of the file.
* There is a virtual hole there. */
assert(errno != -ENXIO);
return 1;
}
if (*hole > start) {
*data = start;
} else {
/* On a hole. We need another syscall to find its end. */
*data = lseek(s->fd, start, SEEK_DATA);
if (*data == -1) {
*data = lseek(s->fd, 0, SEEK_END);
}
}
return 0;
#else
return 1;
#endif
}
/*
* Returns true iff the specified sector is present in the disk image. Drivers
* not implementing the functionality are assumed to not support backing files,
@@ -1054,7 +1130,7 @@ static int coroutine_fn raw_co_is_allocated(BlockDriverState *bs,
int64_t sector_num,
int nb_sectors, int *pnum)
{
off_t start, data, hole;
off_t start, data = 0, hole = 0;
int ret;
ret = fd_open(bs);
@@ -1064,65 +1140,15 @@ static int coroutine_fn raw_co_is_allocated(BlockDriverState *bs,
start = sector_num * BDRV_SECTOR_SIZE;
#ifdef CONFIG_FIEMAP
BDRVRawState *s = bs->opaque;
struct {
struct fiemap fm;
struct fiemap_extent fe;
} f;
f.fm.fm_start = start;
f.fm.fm_length = (int64_t)nb_sectors * BDRV_SECTOR_SIZE;
f.fm.fm_flags = 0;
f.fm.fm_extent_count = 1;
f.fm.fm_reserved = 0;
if (ioctl(s->fd, FS_IOC_FIEMAP, &f) == -1) {
/* Assume everything is allocated. */
*pnum = nb_sectors;
return 1;
}
if (f.fm.fm_mapped_extents == 0) {
/* No extents found, data is beyond f.fm.fm_start + f.fm.fm_length.
* f.fm.fm_start + f.fm.fm_length must be clamped to the file size!
*/
off_t length = lseek(s->fd, 0, SEEK_END);
hole = f.fm.fm_start;
data = MIN(f.fm.fm_start + f.fm.fm_length, length);
} else {
data = f.fe.fe_logical;
hole = f.fe.fe_logical + f.fe.fe_length;
}
#elif defined SEEK_HOLE && defined SEEK_DATA
BDRVRawState *s = bs->opaque;
hole = lseek(s->fd, start, SEEK_HOLE);
if (hole == -1) {
/* -ENXIO indicates that sector_num was past the end of the file.
* There is a virtual hole there. */
assert(errno != -ENXIO);
/* Most likely EINVAL. Assume everything is allocated. */
*pnum = nb_sectors;
return 1;
}
if (hole > start) {
data = start;
} else {
/* On a hole. We need another syscall to find its end. */
data = lseek(s->fd, start, SEEK_DATA);
if (data == -1) {
data = lseek(s->fd, 0, SEEK_END);
ret = try_fiemap(bs, start, &data, &hole, nb_sectors, pnum);
if (ret) {
ret = try_seek_hole(bs, start, &data, &hole, pnum);
if (ret) {
/* Assume everything is allocated. */
data = 0;
hole = start + nb_sectors * BDRV_SECTOR_SIZE;
}
}
#else
*pnum = nb_sectors;
return 1;
#endif
if (data <= start) {
/* On a data extent, compute sectors to the end of the extent. */