From a659979328fb6d4d6100d398f5bd9a2310c3e169 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Tue, 17 May 2011 18:04:06 +0200 Subject: [PATCH] block: clarify the meaning of BDRV_O_NOCACHE Change BDRV_O_NOCACHE to only imply bypassing the host OS file cache, but no writeback semantics. All existing callers are changed to also specify BDRV_O_CACHE_WB to give them writeback semantics. Signed-off-by: Christoph Hellwig Signed-off-by: Kevin Wolf --- block.c | 8 +------- block/qcow2.c | 2 +- block/raw-posix.c | 2 +- block/raw-win32.c | 12 ++++++------ blockdev.c | 2 +- qemu-io.c | 4 ++-- qemu-nbd.c | 2 +- 7 files changed, 13 insertions(+), 19 deletions(-) diff --git a/block.c b/block.c index effa86fd5..3036a2dee 100644 --- a/block.c +++ b/block.c @@ -439,13 +439,7 @@ static int bdrv_open_common(BlockDriverState *bs, const char *filename, bs->drv = drv; bs->opaque = qemu_mallocz(drv->instance_size); - /* - * Yes, BDRV_O_NOCACHE aka O_DIRECT means we have to present a - * write cache to the guest. We do need the fdatasync to flush - * out transactions for block allocations, and we maybe have a - * volatile write cache in our backing device to deal with. - */ - if (flags & (BDRV_O_CACHE_WB|BDRV_O_NOCACHE)) + if (flags & BDRV_O_CACHE_WB) bs->enable_write_cache = 1; /* diff --git a/block/qcow2.c b/block/qcow2.c index 75b8becc0..db1931b95 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -229,7 +229,7 @@ static int qcow2_open(BlockDriverState *bs, int flags) } /* alloc L2 table/refcount block cache */ - writethrough = ((flags & BDRV_O_CACHE_MASK) == 0); + writethrough = ((flags & BDRV_O_CACHE_WB) == 0); s->l2_table_cache = qcow2_cache_create(bs, L2_CACHE_SIZE, writethrough); s->refcount_block_cache = qcow2_cache_create(bs, REFCOUNT_CACHE_SIZE, writethrough); diff --git a/block/raw-posix.c b/block/raw-posix.c index 6b7247059..50428fdbb 100644 --- a/block/raw-posix.c +++ b/block/raw-posix.c @@ -154,7 +154,7 @@ static int raw_open_common(BlockDriverState *bs, const char *filename, * and O_DIRECT for no caching. */ if ((bdrv_flags & BDRV_O_NOCACHE)) s->open_flags |= O_DIRECT; - else if (!(bdrv_flags & BDRV_O_CACHE_WB)) + if (!(bdrv_flags & BDRV_O_CACHE_WB)) s->open_flags |= O_DSYNC; s->fd = -1; diff --git a/block/raw-win32.c b/block/raw-win32.c index c204a80d7..56bd7195a 100644 --- a/block/raw-win32.c +++ b/block/raw-win32.c @@ -88,9 +88,9 @@ static int raw_open(BlockDriverState *bs, const char *filename, int flags) } overlapped = FILE_ATTRIBUTE_NORMAL; - if ((flags & BDRV_O_NOCACHE)) - overlapped |= FILE_FLAG_NO_BUFFERING | FILE_FLAG_WRITE_THROUGH; - else if (!(flags & BDRV_O_CACHE_WB)) + if (flags & BDRV_O_NOCACHE) + overlapped |= FILE_FLAG_NO_BUFFERING; + if (!(flags & BDRV_O_CACHE_WB)) overlapped |= FILE_FLAG_WRITE_THROUGH; s->hfile = CreateFile(filename, access_flags, FILE_SHARE_READ, NULL, @@ -349,9 +349,9 @@ static int hdev_open(BlockDriverState *bs, const char *filename, int flags) create_flags = OPEN_EXISTING; overlapped = FILE_ATTRIBUTE_NORMAL; - if ((flags & BDRV_O_NOCACHE)) - overlapped |= FILE_FLAG_NO_BUFFERING | FILE_FLAG_WRITE_THROUGH; - else if (!(flags & BDRV_O_CACHE_WB)) + if (flags & BDRV_O_NOCACHE) + overlapped |= FILE_FLAG_NO_BUFFERING; + if (!(flags & BDRV_O_CACHE_WB)) overlapped |= FILE_FLAG_WRITE_THROUGH; s->hfile = CreateFile(filename, access_flags, FILE_SHARE_READ, NULL, diff --git a/blockdev.c b/blockdev.c index 6e0eb831c..1502575ac 100644 --- a/blockdev.c +++ b/blockdev.c @@ -326,7 +326,7 @@ DriveInfo *drive_init(QemuOpts *opts, int default_to_scsi) if ((buf = qemu_opt_get(opts, "cache")) != NULL) { if (!strcmp(buf, "off") || !strcmp(buf, "none")) { - bdrv_flags |= BDRV_O_NOCACHE; + bdrv_flags |= BDRV_O_NOCACHE | BDRV_O_CACHE_WB; } else if (!strcmp(buf, "writeback")) { bdrv_flags |= BDRV_O_CACHE_WB; } else if (!strcmp(buf, "unsafe")) { diff --git a/qemu-io.c b/qemu-io.c index 4470e49bc..dd4ebf537 100644 --- a/qemu-io.c +++ b/qemu-io.c @@ -1655,7 +1655,7 @@ open_f(int argc, char **argv) flags |= BDRV_O_SNAPSHOT; break; case 'n': - flags |= BDRV_O_NOCACHE; + flags |= BDRV_O_NOCACHE | BDRV_O_CACHE_WB; break; case 'r': readonly = 1; @@ -1751,7 +1751,7 @@ int main(int argc, char **argv) flags |= BDRV_O_SNAPSHOT; break; case 'n': - flags |= BDRV_O_NOCACHE; + flags |= BDRV_O_NOCACHE | BDRV_O_CACHE_WB; break; case 'c': add_user_command(optarg); diff --git a/qemu-nbd.c b/qemu-nbd.c index e858033e0..110d78e6a 100644 --- a/qemu-nbd.c +++ b/qemu-nbd.c @@ -238,7 +238,7 @@ int main(int argc, char **argv) flags |= BDRV_O_SNAPSHOT; break; case 'n': - flags |= BDRV_O_NOCACHE; + flags |= BDRV_O_NOCACHE | BDRV_O_CACHE_WB; break; case 'b': bindto = optarg; -- 2.39.5