diff options
| author | Kevin Wolf <kwolf@redhat.com> | 2018-06-21 17:54:35 +0200 |
|---|---|---|
| committer | Kevin Wolf <kwolf@redhat.com> | 2018-06-29 14:20:56 +0200 |
| commit | 061ca8a368165fae300748c17971824a089f521f (patch) | |
| tree | 94e2fb34999021ead20698bf7399ae151d13047b /block/qed.c | |
| parent | ae5475e82fd1ebb24f4f77cf28f59ca6548c6136 (diff) | |
block: Convert .bdrv_truncate callback to coroutine_fn
bdrv_truncate() is an operation that can block (even for a quite long
time, depending on the PreallocMode) in I/O paths that shouldn't block.
Convert it to a coroutine_fn so that we have the infrastructure for
drivers to make their .bdrv_co_truncate implementation asynchronous.
This change could potentially introduce new race conditions because
bdrv_truncate() isn't necessarily executed atomically any more. Whether
this is a problem needs to be evaluated for each block driver that
supports truncate:
* file-posix/win32, gluster, iscsi, nfs, rbd, ssh, sheepdog: The
protocol drivers are trivially safe because they don't actually yield
yet, so there is no change in behaviour.
* copy-on-read, crypto, raw-format: Essentially just filter drivers that
pass the request to a child node, no problem.
* qcow2: The implementation modifies metadata, so it needs to hold
s->lock to be safe with concurrent I/O requests. In order to avoid
double locking, this requires pulling the locking out into
preallocate_co() and using qcow2_write_caches() instead of
bdrv_flush().
* qed: Does a single header update, this is fine without locking.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Diffstat (limited to 'block/qed.c')
| -rw-r--r-- | block/qed.c | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/block/qed.c b/block/qed.c index 2363814538..689ea9d4d5 100644 --- a/block/qed.c +++ b/block/qed.c @@ -1467,8 +1467,10 @@ static int coroutine_fn bdrv_qed_co_pwrite_zeroes(BlockDriverState *bs, QED_AIOCB_WRITE | QED_AIOCB_ZERO); } -static int bdrv_qed_truncate(BlockDriverState *bs, int64_t offset, - PreallocMode prealloc, Error **errp) +static int coroutine_fn bdrv_qed_co_truncate(BlockDriverState *bs, + int64_t offset, + PreallocMode prealloc, + Error **errp) { BDRVQEDState *s = bs->opaque; uint64_t old_image_size; @@ -1678,7 +1680,7 @@ static BlockDriver bdrv_qed = { .bdrv_co_readv = bdrv_qed_co_readv, .bdrv_co_writev = bdrv_qed_co_writev, .bdrv_co_pwrite_zeroes = bdrv_qed_co_pwrite_zeroes, - .bdrv_truncate = bdrv_qed_truncate, + .bdrv_co_truncate = bdrv_qed_co_truncate, .bdrv_getlength = bdrv_qed_getlength, .bdrv_get_info = bdrv_qed_get_info, .bdrv_refresh_limits = bdrv_qed_refresh_limits, |