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authorKevin Wolf <kwolf@redhat.com>2018-06-21 17:54:35 +0200
committerKevin Wolf <kwolf@redhat.com>2018-06-29 14:20:56 +0200
commit061ca8a368165fae300748c17971824a089f521f (patch)
tree94e2fb34999021ead20698bf7399ae151d13047b /block/copy-on-read.c
parentae5475e82fd1ebb24f4f77cf28f59ca6548c6136 (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/copy-on-read.c')
-rw-r--r--block/copy-on-read.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/block/copy-on-read.c b/block/copy-on-read.c
index 6a97208888..1dcdaeed69 100644
--- a/block/copy-on-read.c
+++ b/block/copy-on-read.c
@@ -80,10 +80,10 @@ static int64_t cor_getlength(BlockDriverState *bs)
}
-static int cor_truncate(BlockDriverState *bs, int64_t offset,
- PreallocMode prealloc, Error **errp)
+static int coroutine_fn cor_co_truncate(BlockDriverState *bs, int64_t offset,
+ PreallocMode prealloc, Error **errp)
{
- return bdrv_truncate(bs->file, offset, prealloc, errp);
+ return bdrv_co_truncate(bs->file, offset, prealloc, errp);
}
@@ -147,7 +147,7 @@ BlockDriver bdrv_copy_on_read = {
.bdrv_child_perm = cor_child_perm,
.bdrv_getlength = cor_getlength,
- .bdrv_truncate = cor_truncate,
+ .bdrv_co_truncate = cor_co_truncate,
.bdrv_co_preadv = cor_co_preadv,
.bdrv_co_pwritev = cor_co_pwritev,