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linux aio: some comments

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Add some notes about Linux AIO explaining why we don't use AIO in
some situations.

Signed-off-by: Frediano Ziglio <freddy77@gmail.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Frediano Ziglio 2011-08-30 09:46:11 +02:00 committed by Kevin Wolf
parent f69539b14b
commit c30e624d5d
2 changed files with 5 additions and 0 deletions
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4
block/raw-posix.c
View File

@ -236,6 +236,10 @@ static int raw_open_common(BlockDriverState *bs, const char *filename,
} }
#ifdef CONFIG_LINUX_AIO #ifdef CONFIG_LINUX_AIO
/*
* Currently Linux do AIO only for files opened with O_DIRECT
* specified so check NOCACHE flag too
*/
if ((bdrv_flags & (BDRV_O_NOCACHE|BDRV_O_NATIVE_AIO)) == if ((bdrv_flags & (BDRV_O_NOCACHE|BDRV_O_NATIVE_AIO)) ==
(BDRV_O_NOCACHE|BDRV_O_NATIVE_AIO)) { (BDRV_O_NOCACHE|BDRV_O_NATIVE_AIO)) {

1
linux-aio.c
View File

@ -181,6 +181,7 @@ BlockDriverAIOCB *laio_submit(BlockDriverState *bs, void *aio_ctx, int fd,
case QEMU_AIO_READ: case QEMU_AIO_READ:
io_prep_preadv(iocbs, fd, qiov->iov, qiov->niov, offset); io_prep_preadv(iocbs, fd, qiov->iov, qiov->niov, offset);
break; break;
/* Currently Linux kernel does not support other operations */
default: default:
fprintf(stderr, "%s: invalid AIO request type 0x%x.\n", fprintf(stderr, "%s: invalid AIO request type 0x%x.\n",
__func__, type); __func__, type);