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[Qemu-devel] [PATCH 2/2] block: untangle open flag manipulation in bdrv_
From: |
Christoph Hellwig |
Subject: |
[Qemu-devel] [PATCH 2/2] block: untangle open flag manipulation in bdrv_open2 |
Date: |
Mon, 11 Jan 2010 18:52:09 +0100 |
User-agent: |
Mutt/1.3.28i |
Untangle the open flag manipulation in bdrv_open2 and document why we
are clearing the various flags in the different flag combinations.
Signed-off-by: Christoph Hellwig <address@hidden>
Index: qemu/block.c
===================================================================
--- qemu.orig/block.c 2010-01-11 17:52:54.273003789 +0100
+++ qemu/block.c 2010-01-11 18:19:22.485006278 +0100
@@ -356,7 +356,7 @@ int bdrv_open(BlockDriverState *bs, cons
int bdrv_open2(BlockDriverState *bs, const char *filename, int flags,
BlockDriver *drv)
{
- int ret, open_flags, try_rw;
+ int ret, open_flags;
char tmp_filename[PATH_MAX];
char backing_filename[PATH_MAX];
@@ -450,19 +450,39 @@ int bdrv_open2(BlockDriverState *bs, con
if (flags & (BDRV_O_CACHE_WB|BDRV_O_NOCACHE))
bs->enable_write_cache = 1;
- /* Note: for compatibility, we open disk image files as RDWR, and
- RDONLY as fallback */
- try_rw = !bs->read_only || bs->is_temporary;
- if (!(flags & BDRV_O_FILE))
- open_flags = (try_rw ? BDRV_O_RDWR : 0) |
- (flags & (BDRV_O_CACHE_MASK|BDRV_O_NATIVE_AIO));
- else
- open_flags = flags & ~(BDRV_O_FILE | BDRV_O_SNAPSHOT);
+ /*
+ * Always clear these flags as they are not destined for the drivers.
+ */
+ open_flags = flags & ~(BDRV_O_FILE | BDRV_O_SNAPSHOT);
+
+ if (!(flags & BDRV_O_FILE)) {
+ /*
+ * For historical reasons we always try to open drive images as
+ * read-write first and only fall back to read-only later.
+ *
+ * This can be overriden using readonly suboption for the
+ * drive option.
+ */
+ if (bs->read_only && !bs->is_temporary) {
+ open_flags &= ~BDRV_O_RDWR;
+ } else {
+ open_flags |= BDRV_O_RDWR;
+ }
- ret = drv->bdrv_open(bs, filename, open_flags);
- if ((ret == -EACCES || ret == -EPERM) && !(flags & BDRV_O_FILE)) {
- ret = drv->bdrv_open(bs, filename, open_flags & ~BDRV_O_RDWR);
- bs->read_only = 1;
+ /*
+ * Currently BDRV_O_CREAT is not supported by any image format,
+ * but I'm not sure that's reason enough to always clear it for
+ * the !BDRV_O_FILE case..
+ */
+ open_flags &= ~(BDRV_O_CREAT);
+
+ ret = drv->bdrv_open(bs, filename, open_flags);
+ if (ret == -EACCES || ret == -EPERM) {
+ ret = drv->bdrv_open(bs, filename, open_flags & ~BDRV_O_RDWR);
+ bs->read_only = 1;
+ }
+ } else {
+ ret = drv->bdrv_open(bs, filename, open_flags);
}
if (ret < 0) {
- [Qemu-devel] [PATCH 2/2] block: untangle open flag manipulation in bdrv_open2,
Christoph Hellwig <=