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[Qemu-devel] [PATCH v2 02/15] block: Allow NULL file for bdrv_get_block_
From: |
Eric Blake |
Subject: |
[Qemu-devel] [PATCH v2 02/15] block: Allow NULL file for bdrv_get_block_status() |
Date: |
Mon, 3 Jul 2017 17:14:43 -0500 |
Not all callers care about which BDS owns the mapping for a given
range of the file. This patch merely simplifies the callers by
consolidating the logic in the common call point, while guaranteeing
a non-NULL file to all the driver callbacks, for no semantic change.
The only caller that does not care about pnum is bdrv_is_allocated,
as invoked by vvfat; we can likewise add assertions that the rest
of the stack does not have to worry about a NULL pnum.
Furthermore, this will also set the stage for a future cleanup: when
a caller does not care about which BDS owns an offset, it would be
nice to allow the driver to optimize things to not have to return
BDRV_BLOCK_OFFSET_VALID in the first place. In the case of fragmented
allocation (for example, it's fairly easy to create a qcow2 image
where consecutive guest addresses are not at consecutive host
addresses), the current contract requires bdrv_get_block_status()
to clamp *pnum to the limit where host addresses are no longer
consecutive, but allowing a NULL file means that *pnum could be
set to the full length of known-allocated data.
Signed-off-by: Eric Blake <address@hidden>
---
v2: use local variable and final transfer, rather than assignment
of parameter to local
[previously in different series]:
v2: new patch,
https://lists.gnu.org/archive/html/qemu-devel/2017-05/msg05645.html
---
include/block/block_int.h | 10 ++++++----
block/io.c | 44 ++++++++++++++++++++++++++++----------------
block/mirror.c | 3 +--
block/qcow2.c | 4 +---
qemu-img.c | 10 ++++------
5 files changed, 40 insertions(+), 31 deletions(-)
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 724799c..ffa22c7 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -168,10 +168,12 @@ struct BlockDriver {
int64_t offset, int bytes);
/*
- * Building block for bdrv_block_status[_above]. The driver should
- * answer only according to the current layer, and should not
- * set BDRV_BLOCK_ALLOCATED, but may set BDRV_BLOCK_RAW. See block.h
- * for the meaning of _DATA, _ZERO, and _OFFSET_VALID.
+ * Building block for bdrv_block_status[_above] and
+ * bdrv_is_allocated[_above]. The driver should answer only
+ * according to the current layer, and should not set
+ * BDRV_BLOCK_ALLOCATED, but may set BDRV_BLOCK_RAW. See block.h
+ * for the meaning of _DATA, _ZERO, and _OFFSET_VALID. The block
+ * layer guarantees non-NULL pnum and file.
*/
int64_t coroutine_fn (*bdrv_co_get_block_status)(BlockDriverState *bs,
int64_t sector_num, int nb_sectors, int *pnum,
diff --git a/block/io.c b/block/io.c
index 8c67ba8..6358d07 100644
--- a/block/io.c
+++ b/block/io.c
@@ -671,7 +671,6 @@ int bdrv_make_zero(BdrvChild *child, BdrvRequestFlags flags)
{
int64_t target_sectors, ret, nb_sectors, sector_num = 0;
BlockDriverState *bs = child->bs;
- BlockDriverState *file;
int n;
target_sectors = bdrv_nb_sectors(bs);
@@ -684,7 +683,7 @@ int bdrv_make_zero(BdrvChild *child, BdrvRequestFlags flags)
if (nb_sectors <= 0) {
return 0;
}
- ret = bdrv_get_block_status(bs, sector_num, nb_sectors, &n, &file);
+ ret = bdrv_get_block_status(bs, sector_num, nb_sectors, &n, NULL);
if (ret < 0) {
error_report("error getting block status at sector %" PRId64 ":
%s",
sector_num, strerror(-ret));
@@ -1729,8 +1728,9 @@ int64_t coroutine_fn
bdrv_co_get_block_status_from_backing(BlockDriverState *bs,
* beyond the end of the disk image it will be clamped; if 'pnum' is set to
* the end of the image, then the returned value will include BDRV_BLOCK_EOF.
*
- * If returned value is positive and BDRV_BLOCK_OFFSET_VALID bit is set, 'file'
- * points to the BDS which the sector range is allocated in.
+ * If returned value is positive, BDRV_BLOCK_OFFSET_VALID bit is set, and
+ * 'file' is non-NULL, then '*file' points to the BDS which the sector range
+ * is allocated in.
*/
static int64_t coroutine_fn bdrv_co_get_block_status(BlockDriverState *bs,
int64_t sector_num,
@@ -1740,15 +1740,22 @@ static int64_t coroutine_fn
bdrv_co_get_block_status(BlockDriverState *bs,
int64_t total_sectors;
int64_t n;
int64_t ret, ret2;
+ BlockDriverState *local_file = NULL;
- *file = NULL;
+ assert(pnum);
total_sectors = bdrv_nb_sectors(bs);
if (total_sectors < 0) {
+ if (file) {
+ *file = NULL;
+ }
return total_sectors;
}
if (sector_num >= total_sectors) {
*pnum = 0;
+ if (file) {
+ *file = NULL;
+ }
return BDRV_BLOCK_EOF;
}
@@ -1765,23 +1772,27 @@ static int64_t coroutine_fn
bdrv_co_get_block_status(BlockDriverState *bs,
}
if (bs->drv->protocol_name) {
ret |= BDRV_BLOCK_OFFSET_VALID | (sector_num * BDRV_SECTOR_SIZE);
- *file = bs;
+ if (file) {
+ *file = bs;
+ }
+ } else if (file) {
+ *file = NULL;
}
return ret;
}
bdrv_inc_in_flight(bs);
ret = bs->drv->bdrv_co_get_block_status(bs, sector_num, nb_sectors, pnum,
- file);
+ &local_file);
if (ret < 0) {
*pnum = 0;
goto out;
}
if (ret & BDRV_BLOCK_RAW) {
- assert(ret & BDRV_BLOCK_OFFSET_VALID && *file);
- ret = bdrv_co_get_block_status(*file, ret >> BDRV_SECTOR_BITS,
- *pnum, pnum, file);
+ assert(ret & BDRV_BLOCK_OFFSET_VALID && local_file);
+ ret = bdrv_co_get_block_status(local_file, ret >> BDRV_SECTOR_BITS,
+ *pnum, pnum, &local_file);
goto out;
}
@@ -1799,14 +1810,13 @@ static int64_t coroutine_fn
bdrv_co_get_block_status(BlockDriverState *bs,
}
}
- if (*file && *file != bs &&
+ if (local_file && local_file != bs &&
(ret & BDRV_BLOCK_DATA) && !(ret & BDRV_BLOCK_ZERO) &&
(ret & BDRV_BLOCK_OFFSET_VALID)) {
- BlockDriverState *file2;
int file_pnum;
- ret2 = bdrv_co_get_block_status(*file, ret >> BDRV_SECTOR_BITS,
- *pnum, &file_pnum, &file2);
+ ret2 = bdrv_co_get_block_status(local_file, ret >> BDRV_SECTOR_BITS,
+ *pnum, &file_pnum, NULL);
if (ret2 >= 0) {
/* Ignore errors. This is just providing extra information, it
* is useful but not necessary.
@@ -1828,6 +1838,9 @@ static int64_t coroutine_fn
bdrv_co_get_block_status(BlockDriverState *bs,
}
out:
+ if (file) {
+ *file = local_file;
+ }
bdrv_dec_in_flight(bs);
if (ret >= 0 && sector_num + *pnum == total_sectors) {
ret |= BDRV_BLOCK_EOF;
@@ -1931,7 +1944,6 @@ int64_t bdrv_get_block_status(BlockDriverState *bs,
int coroutine_fn bdrv_is_allocated(BlockDriverState *bs, int64_t offset,
int64_t bytes, int64_t *pnum)
{
- BlockDriverState *file;
int64_t sector_num = offset >> BDRV_SECTOR_BITS;
int nb_sectors = bytes >> BDRV_SECTOR_BITS;
int64_t ret;
@@ -1941,7 +1953,7 @@ int coroutine_fn bdrv_is_allocated(BlockDriverState *bs,
int64_t offset,
assert(QEMU_IS_ALIGNED(bytes, BDRV_SECTOR_SIZE) &&
bytes < INT_MAX * BDRV_SECTOR_SIZE);
ret = bdrv_get_block_status(bs, sector_num, nb_sectors, &psectors,
- &file);
+ NULL);
if (ret < 0) {
return ret;
}
diff --git a/block/mirror.c b/block/mirror.c
index 4e883bc..21758a8 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -391,7 +391,6 @@ static uint64_t coroutine_fn
mirror_iteration(MirrorBlockJob *s)
int io_sectors;
unsigned int io_bytes;
int64_t io_bytes_acct;
- BlockDriverState *file;
enum MirrorMethod {
MIRROR_METHOD_COPY,
MIRROR_METHOD_ZERO,
@@ -402,7 +401,7 @@ static uint64_t coroutine_fn
mirror_iteration(MirrorBlockJob *s)
ret = bdrv_get_block_status_above(source, NULL,
offset >> BDRV_SECTOR_BITS,
nb_chunks * sectors_per_chunk,
- &io_sectors, &file);
+ &io_sectors, NULL);
io_bytes = io_sectors * BDRV_SECTOR_SIZE;
if (ret < 0) {
io_bytes = MIN(nb_chunks * s->granularity, max_io_bytes);
diff --git a/block/qcow2.c b/block/qcow2.c
index 9d3c70e..d75f248 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -2909,7 +2909,6 @@ static bool is_zero_sectors(BlockDriverState *bs, int64_t
start,
uint32_t count)
{
int nr;
- BlockDriverState *file;
int64_t res;
if (start + count > bs->total_sectors) {
@@ -2919,8 +2918,7 @@ static bool is_zero_sectors(BlockDriverState *bs, int64_t
start,
if (!count) {
return true;
}
- res = bdrv_get_block_status_above(bs, NULL, start, count,
- &nr, &file);
+ res = bdrv_get_block_status_above(bs, NULL, start, count, &nr, NULL);
return res >= 0 && (res & BDRV_BLOCK_ZERO) && nr == count;
}
diff --git a/qemu-img.c b/qemu-img.c
index 8def1e8..daba954 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -1373,7 +1373,6 @@ static int img_compare(int argc, char **argv)
for (;;) {
int64_t status1, status2;
- BlockDriverState *file;
nb_sectors = sectors_to_process(total_sectors, sector_num);
if (nb_sectors <= 0) {
@@ -1381,7 +1380,7 @@ static int img_compare(int argc, char **argv)
}
status1 = bdrv_get_block_status_above(bs1, NULL, sector_num,
total_sectors1 - sector_num,
- &pnum1, &file);
+ &pnum1, NULL);
if (status1 < 0) {
ret = 3;
error_report("Sector allocation test failed for %s", filename1);
@@ -1391,7 +1390,7 @@ static int img_compare(int argc, char **argv)
status2 = bdrv_get_block_status_above(bs2, NULL, sector_num,
total_sectors2 - sector_num,
- &pnum2, &file);
+ &pnum2, NULL);
if (status2 < 0) {
ret = 3;
error_report("Sector allocation test failed for %s", filename2);
@@ -1594,15 +1593,14 @@ static int convert_iteration_sectors(ImgConvertState
*s, int64_t sector_num)
n = MIN(s->total_sectors - sector_num, BDRV_REQUEST_MAX_SECTORS);
if (s->sector_next_status <= sector_num) {
- BlockDriverState *file;
if (s->target_has_backing) {
ret = bdrv_get_block_status(blk_bs(s->src[src_cur]),
sector_num - src_cur_offset,
- n, &n, &file);
+ n, &n, NULL);
} else {
ret = bdrv_get_block_status_above(blk_bs(s->src[src_cur]), NULL,
sector_num - src_cur_offset,
- n, &n, &file);
+ n, &n, NULL);
}
if (ret < 0) {
return ret;
--
2.9.4
- Re: [Qemu-devel] [PATCH v2 01/15] block: add default implementations for bdrv_co_get_block_status(), (continued)
Re: [Qemu-devel] [PATCH v2 03/15] block: Add flag to avoid wasted work in bdrv_is_allocated(), Eric Blake, 2017/07/05
[Qemu-devel] [PATCH v2 02/15] block: Allow NULL file for bdrv_get_block_status(),
Eric Blake <=
[Qemu-devel] [PATCH v2 05/15] qcow2: Switch is_zero_sectors() to byte-based, Eric Blake, 2017/07/03
[Qemu-devel] [PATCH v2 06/15] block: Switch bdrv_make_zero() to byte-based, Eric Blake, 2017/07/03
[Qemu-devel] [PATCH v2 07/15] qemu-img: Switch get_block_status() to byte-based, Eric Blake, 2017/07/03
[Qemu-devel] [PATCH v2 08/15] block: Convert bdrv_get_block_status() to bytes, Eric Blake, 2017/07/03
[Qemu-devel] [PATCH v2 09/15] block: Switch bdrv_co_get_block_status() to byte-based, Eric Blake, 2017/07/03