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authorEric Blake <eblake@redhat.com>2017-07-07 07:44:57 -0500
committerKevin Wolf <kwolf@redhat.com>2017-07-10 13:18:07 +0200
commitd6a644bbfef81bb6c7ab11656ad71e326f75ac77 (patch)
tree51e6a34d23229e6b01bf0c1fb81d6782854a07e8 /block/commit.c
parent6f8e35e2414433a56b4bd548b87b8ac2aedecb77 (diff)
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block: Make bdrv_is_allocated() byte-based
We are gradually moving away from sector-based interfaces, towards byte-based. In the common case, allocation is unlikely to ever use values that are not naturally sector-aligned, but it is possible that byte-based values will let us be more precise about allocation at the end of an unaligned file that can do byte-based access. Changing the signature of the function to use int64_t *pnum ensures that the compiler enforces that all callers are updated. For now, the io.c layer still assert()s that all callers are sector-aligned on input and that *pnum is sector-aligned on return to the caller, but that can be relaxed when a later patch implements byte-based block status. Therefore, this code adds usages like DIV_ROUND_UP(,BDRV_SECTOR_SIZE) to callers that still want aligned values, where the call might reasonbly give non-aligned results in the future; on the other hand, no rounding is needed for callers that should just continue to work with byte alignment. For the most part this patch is just the addition of scaling at the callers followed by inverse scaling at bdrv_is_allocated(). But some code, particularly bdrv_commit(), gets a lot simpler because it no longer has to mess with sectors; also, it is now possible to pass NULL if the caller does not care how much of the image is allocated beyond the initial offset. Leave comments where we can further simplify once a later patch eliminates the need for sector-aligned requests through bdrv_is_allocated(). For ease of review, bdrv_is_allocated_above() will be tackled separately. Signed-off-by: Eric Blake <eblake@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'block/commit.c')
-rw-r--r--block/commit.c21
1 files changed, 9 insertions, 12 deletions
diff --git a/block/commit.c b/block/commit.c
index c3a7bca..241aa95 100644
--- a/block/commit.c
+++ b/block/commit.c
@@ -443,7 +443,7 @@ fail:
}
-#define COMMIT_BUF_SECTORS 2048
+#define COMMIT_BUF_SIZE (2048 * BDRV_SECTOR_SIZE)
/* commit COW file into the raw image */
int bdrv_commit(BlockDriverState *bs)
@@ -452,8 +452,9 @@ int bdrv_commit(BlockDriverState *bs)
BlockDriverState *backing_file_bs = NULL;
BlockDriverState *commit_top_bs = NULL;
BlockDriver *drv = bs->drv;
- int64_t sector, total_sectors, length, backing_length;
- int n, ro, open_flags;
+ int64_t offset, length, backing_length;
+ int ro, open_flags;
+ int64_t n;
int ret = 0;
uint8_t *buf = NULL;
Error *local_err = NULL;
@@ -531,30 +532,26 @@ int bdrv_commit(BlockDriverState *bs)
}
}
- total_sectors = length >> BDRV_SECTOR_BITS;
-
/* blk_try_blockalign() for src will choose an alignment that works for
* backing as well, so no need to compare the alignment manually. */
- buf = blk_try_blockalign(src, COMMIT_BUF_SECTORS * BDRV_SECTOR_SIZE);
+ buf = blk_try_blockalign(src, COMMIT_BUF_SIZE);
if (buf == NULL) {
ret = -ENOMEM;
goto ro_cleanup;
}
- for (sector = 0; sector < total_sectors; sector += n) {
- ret = bdrv_is_allocated(bs, sector, COMMIT_BUF_SECTORS, &n);
+ for (offset = 0; offset < length; offset += n) {
+ ret = bdrv_is_allocated(bs, offset, COMMIT_BUF_SIZE, &n);
if (ret < 0) {
goto ro_cleanup;
}
if (ret) {
- ret = blk_pread(src, sector * BDRV_SECTOR_SIZE, buf,
- n * BDRV_SECTOR_SIZE);
+ ret = blk_pread(src, offset, buf, n);
if (ret < 0) {
goto ro_cleanup;
}
- ret = blk_pwrite(backing, sector * BDRV_SECTOR_SIZE, buf,
- n * BDRV_SECTOR_SIZE, 0);
+ ret = blk_pwrite(backing, offset, buf, n, 0);
if (ret < 0) {
goto ro_cleanup;
}