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block: access copy_on_read with atomic ops 

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20170605123908.18777-2-pbonzini@redhat.com>
Signed-off-by: Fam Zheng <famz@redhat.com>
This commit is contained in:
Paolo Bonzini 2017-06-05 14:38:50 +02:00 committed by Fam Zheng
parent 79f24568e5
commit d3faa13e5f
4 changed files with 15 additions and 12 deletions
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6
block.c
View File

@ -1300,7 +1300,9 @@ static int bdrv_open_common(BlockDriverState *bs, BlockBackend *file,
goto fail_opts; goto fail_opts;
} }
assert(bs->copy_on_read == 0); /* bdrv_new() and bdrv_close() make it so */ /* bdrv_new() and bdrv_close() make it so */
assert(atomic_read(&bs->copy_on_read) == 0);
if (bs->open_flags & BDRV_O_COPY_ON_READ) { if (bs->open_flags & BDRV_O_COPY_ON_READ) {
if (!bs->read_only) { if (!bs->read_only) {
bdrv_enable_copy_on_read(bs); bdrv_enable_copy_on_read(bs);
@ -3063,7 +3065,7 @@ static void bdrv_close(BlockDriverState *bs)
g_free(bs->opaque); g_free(bs->opaque);
bs->opaque = NULL; bs->opaque = NULL;
bs->copy_on_read = 0; atomic_set(&bs->copy_on_read, 0);
bs->backing_file[0] = '\0'; bs->backing_file[0] = '\0';
bs->backing_format[0] = '\0'; bs->backing_format[0] = '\0';
bs->total_sectors = 0; bs->total_sectors = 0;

8
block/io.c
View File

@ -130,13 +130,13 @@ void bdrv_refresh_limits(BlockDriverState *bs, Error **errp)
*/ */
void bdrv_enable_copy_on_read(BlockDriverState *bs) void bdrv_enable_copy_on_read(BlockDriverState *bs)
{ {
bs->copy_on_read++; atomic_inc(&bs->copy_on_read);
} }
void bdrv_disable_copy_on_read(BlockDriverState *bs) void bdrv_disable_copy_on_read(BlockDriverState *bs)
{ {
assert(bs->copy_on_read > 0); int old = atomic_fetch_dec(&bs->copy_on_read);
bs->copy_on_read--; assert(old >= 1);
} }
/* Check if any requests are in-flight (including throttled requests) */ /* Check if any requests are in-flight (including throttled requests) */
@ -1144,7 +1144,7 @@ int coroutine_fn bdrv_co_preadv(BdrvChild *child,
bdrv_inc_in_flight(bs); bdrv_inc_in_flight(bs);
/* Don't do copy-on-read if we read data before write operation */ /* Don't do copy-on-read if we read data before write operation */
if (bs->copy_on_read && !(flags & BDRV_REQ_NO_SERIALISING)) { if (atomic_read(&bs->copy_on_read) && !(flags & BDRV_REQ_NO_SERIALISING)) {
flags |= BDRV_REQ_COPY_ON_READ; flags |= BDRV_REQ_COPY_ON_READ;
} }

2
blockdev.c
View File

@ -1791,7 +1791,7 @@ static void external_snapshot_commit(BlkActionState *common)
/* We don't need (or want) to use the transactional /* We don't need (or want) to use the transactional
* bdrv_reopen_multiple() across all the entries at once, because we * bdrv_reopen_multiple() across all the entries at once, because we
* don't want to abort all of them if one of them fails the reopen */ * don't want to abort all of them if one of them fails the reopen */
if (!state->old_bs->copy_on_read) { if (!atomic_read(&state->old_bs->copy_on_read)) {
bdrv_reopen(state->old_bs, state->old_bs->open_flags & ~BDRV_O_RDWR, bdrv_reopen(state->old_bs, state->old_bs->open_flags & ~BDRV_O_RDWR,
NULL); NULL);
} }

11
include/block/block_int.h
View File

@ -595,11 +595,6 @@ struct BlockDriverState {
/* Protected by AioContext lock */ /* Protected by AioContext lock */
/* If true, copy read backing sectors into image. Can be >1 if more
* than one client has requested copy-on-read.
*/
int copy_on_read;
/* If we are reading a disk image, give its size in sectors. /* If we are reading a disk image, give its size in sectors.
* Generally read-only; it is written to by load_snapshot and * Generally read-only; it is written to by load_snapshot and
* save_snaphost, but the block layer is quiescent during those. * save_snaphost, but the block layer is quiescent during those.
@ -633,6 +628,12 @@ struct BlockDriverState {
QLIST_HEAD(, BdrvDirtyBitmap) dirty_bitmaps; QLIST_HEAD(, BdrvDirtyBitmap) dirty_bitmaps;
/* If true, copy read backing sectors into image. Can be >1 if more
* than one client has requested copy-on-read. Accessed with atomic
* ops.
*/
int copy_on_read;
/* do we need to tell the quest if we have a volatile write cache? */ /* do we need to tell the quest if we have a volatile write cache? */
int enable_write_cache; int enable_write_cache;