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block: correctly set the keep_read_only flag

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I believe the bs->keep_read_only flag is supposed to reflect
the initial open state of the device. If the device is initially
opened R/O, then commit operations, or reopen operations changing
to R/W, are prohibited.

Currently, the keep_read_only flag is only accurate for the active
layer, and its backing file. Subsequent images end up always having
the keep_read_only flag set.

For instance, what happens now:

[  base  ]  kro = 1, ro = 1
    |
    v
[ snap-1 ]  kro = 1, ro = 1
    |
    v
[ snap-2 ]  kro = 0, ro = 1
    |
    v
[ active ]  kro = 0, ro = 0

What we want:

[  base  ]  kro = 0, ro = 1
    |
    v
[ snap-1 ]  kro = 0, ro = 1
    |
    v
[ snap-2 ]  kro = 0, ro = 1
    |
    v
[ active ]  kro = 0, ro = 0

Signed-off-by: Jeff Cody <jcody@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Jeff Cody 2012-09-20 15:13:17 -04:00 • committed by Kevin Wolf
parent 80dd1aae36
commit be028adced
2 changed files with 8 additions and 7 deletions
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1
block.h
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@ -80,6 +80,7 @@ typedef struct BlockDevOps {
#define BDRV_O_COPY_ON_READ 0x0400 /* copy read backing sectors into image */
#define BDRV_O_INCOMING 0x0800 /* consistency hint for incoming migration */
#define BDRV_O_CHECK 0x1000 /* open solely for consistency check */
#define BDRV_O_ALLOW_RDWR 0x2000 /* allow reopen to change from r/o to r/w */
#define BDRV_O_CACHE_MASK (BDRV_O_NOCACHE | BDRV_O_CACHE_WB | BDRV_O_NO_FLUSH)