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qemu: Clean up description for qemuStorageLimitsRefresh

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Originally added by commit id '89646e69' prior to commit id '15fa84ac'
and '71d2c172' which ensured that qemuStorageLimitsRefresh was only called
for inactive domains.

Adjust the comment describing the need for FIXME and move all the text
to the function description.

Signed-off-by: John Ferlan <jferlan@redhat.com>
This commit is contained in:
John Ferlan 2016-12-01 07:13:15 -05:00
parent a73e7037e5
commit 7149d1693d
1 changed files with 28 additions and 23 deletions
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51
src/qemu/qemu_driver.c
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@ -11542,9 +11542,34 @@ qemuDomainMemoryPeek(virDomainPtr dom,
}
/* Refresh the capacity and allocation limits of a given storage
* source. Assumes that the caller has already obtained a domain
* job. */
/**
* @driver: qemu driver data
* @cfg: driver configuration data
* @vm: domain object
* @src: storage source data
*
* Refresh the capacity and allocation limits of a given storage source.
*
* Assumes that the caller has already obtained a domain job and only
* called for an offline domain. Being offline is particularly important
* since reading a file while qemu is writing it risks the reader seeing
* bogus data or avoiding opening a file in order to get stat data.
*
* We always want to check current on-disk statistics (as users have been
* known to change offline images behind our backs).
*
* For read-only disks, nothing should be changing unless the user has
* requested a block-commit action. For read-write disks, we know some
* special cases: capacity should not change without a block-resize (where
* capacity is the only stat that requires reading a file, and even then,
* only for non-raw files); and physical size of a raw image or of a
* block device should likewise not be changing without block-resize.
* On the other hand, allocation of a raw file can change (if the file
* is sparse, but the amount of sparseness changes due to writes or
* punching holes), and physical size of a non-raw file can change.
*
* Returns 0 on success, -1 on failure
*/
static int
qemuStorageLimitsRefresh(virQEMUDriverPtr driver,
virQEMUDriverConfigPtr cfg,
@ -11560,26 +11585,6 @@ qemuStorageLimitsRefresh(virQEMUDriverPtr driver,
char *buf = NULL;
ssize_t len;
/* FIXME: For an offline domain, we always want to check current
* on-disk statistics (as users have been known to change offline
* images behind our backs). For a running domain, however, it
* would be nice to avoid opening a file (particularly since
* reading a file while qemu is writing it risks the reader seeing
* bogus data), or even avoid a stat, if the information
* remembered from the previous run is still viable.
*
* For read-only disks, nothing should be changing unless the user
* has requested a block-commit action. For read-write disks, we
* know some special cases: capacity should not change without a
* block-resize (where capacity is the only stat that requires
* reading a file, and even then, only for non-raw files); and
* physical size of a raw image or of a block device should
* likewise not be changing without block-resize. On the other
* hand, allocation of a raw file can change (if the file is
* sparse, but the amount of sparseness changes due to writes or
* punching holes), and physical size of a non-raw file can
* change.
*/
if (virStorageSourceIsLocalStorage(src)) {
if ((fd = qemuOpenFile(driver, vm, src->path, O_RDONLY,
NULL, NULL)) == -1)