Re: [libvirt] [PATCHv4 8/8] storage: probe qcow2 volumes in gluster pool
On 11/25/2013 08:59 AM, Daniel P. Berrange wrote:
On Fri, Nov 22, 2013 at 08:20:30PM -0700, Eric Blake wrote:
> Putting together pieces from previous patches, it is now possible
> for 'virsh vol-dumpxml --pool gluster volname' to report metadata
> about a qcow2 file stored on gluster. The backing file is still
> treated as raw; to fix that, more patches are needed to make the
> storage backing chain analysis recursive rather than halting at
> a network protocol name, but that work will not need any further
> calls into libgfapi so much as just reusing this code, and that
> should be the only code outside of the storage driver that needs
> any help from libgfapi. Any additional use of libgfapi within
> libvirt should only be needed for implementing storage pool APIs
> such as volume creation or resizing, where backing chain analysis
> should be unaffected.
>
> + while (maxlen) {
> + ssize_t r = glfs_read(fd, s, maxlen, 0);
> + if (r < 0 && errno == EINTR)
> + continue;
> + if (r < 0) {
> + VIR_FREE(*buf);
> + virReportSystemError(errno, _("unable to read '%s'"),
name);
> + return r;
> + }
Further down you're requesting O_NONBLOCK, and here you are
not handling EAGAIN explicitly. Is is desirable that we turn
EAGAIN into a fatal error, or should we remove the O_NONBLOCK
flag ?
Hmm. I was copying from directory pools, which also use O_NONBLOCK then
call into virFileReadHeaderFD. So that code needs to be fixed (separate
patch). For gluster, I think it's easiest to just drop O_NONBLOCK from
the code (I just verified that attempts to use 'mkfifo' inside a gluster
volume fail with EACCES); for directory pools you DO want to open
O_NONBLOCK (otherwise opening a fifo for read would hang waiting for a
writer), then use virSetNonBlock() after verifying file type but before
reading the header (since we already reject fifos as unable to be used
as a storage volume).
Squashing in this, then pushing.
diff --git i/src/storage/storage_backend_gluster.c
w/src/storage/storage_backend_gluster.c
index 71edb12..7e5ea9e 100644
--- i/src/storage/storage_backend_gluster.c
+++ w/src/storage/storage_backend_gluster.c
@@ -245,7 +245,9 @@
virStorageBackendGlusterRefreshVol(virStorageBackendGlusterStatePtr state,
vol->type = VIR_STORAGE_VOL_NETWORK;
vol->target.format = VIR_STORAGE_FILE_RAW;
- if (!(fd = glfs_open(state->vol, name, O_RDONLY| O_NONBLOCK |
O_NOCTTY))) {
+ /* No need to worry about O_NONBLOCK - gluster doesn't allow creation
+ * of fifos, so there's nothing it would protect us from. */
+ if (!(fd = glfs_open(state->vol, name, O_RDONLY | O_NOCTTY))) {
/* A dangling symlink now implies a TOCTTOU race; report it. */
virReportSystemError(errno, _("cannot open volume '%s'"),
name);
goto cleanup;
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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