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authorJeff Cody <jcody@redhat.com>2016-04-05 10:40:09 -0400
committerJeff Cody <jcody@redhat.com>2016-04-19 12:24:59 -0400
commitd85fa9eb87ba736d2d5ce342fc35f507c8fe29f2 (patch)
treeb5526240fd70adc449d032a58edd035c4abc2c3e
parent5d4343e6c2682fb7fe66f1560d1823b5a26e7b2f (diff)
downloadqemu-arm-d85fa9eb87ba736d2d5ce342fc35f507c8fe29f2.tar.gz
block/gluster: prevent data loss after i/o error
Upon receiving an I/O error after an fsync, by default gluster will dump its cache. However, QEMU will retry the fsync, which is especially useful when encountering errors such as ENOSPC when using the werror=stop option. When using caching with gluster, however, the last written data will be lost upon encountering ENOSPC. Using the write-behind-cache xlator option of 'resync-failed-syncs-after-fsync' should cause gluster to retain the cached data after a failed fsync, so that ENOSPC and other transient errors are recoverable. Unfortunately, we have no way of knowing if the 'resync-failed-syncs-after-fsync' xlator option is supported, so for now close the fd and set the BDS driver to NULL upon fsync error. Signed-off-by: Jeff Cody <jcody@redhat.com>
-rw-r--r--block/gluster.c53
-rwxr-xr-xconfigure8
2 files changed, 60 insertions, 1 deletions
diff --git a/block/gluster.c b/block/gluster.c
index d9aace6253..a8aaacf645 100644
--- a/block/gluster.c
+++ b/block/gluster.c
@@ -314,6 +314,23 @@ static int qemu_gluster_open(BlockDriverState *bs, QDict *options,
goto out;
}
+#ifdef CONFIG_GLUSTERFS_XLATOR_OPT
+ /* Without this, if fsync fails for a recoverable reason (for instance,
+ * ENOSPC), gluster will dump its cache, preventing retries. This means
+ * almost certain data loss. Not all gluster versions support the
+ * 'resync-failed-syncs-after-fsync' key value, but there is no way to
+ * discover during runtime if it is supported (this api returns success for
+ * unknown key/value pairs) */
+ ret = glfs_set_xlator_option(s->glfs, "*-write-behind",
+ "resync-failed-syncs-after-fsync",
+ "on");
+ if (ret < 0) {
+ error_setg_errno(errp, errno, "Unable to set xlator key/value pair");
+ ret = -errno;
+ goto out;
+ }
+#endif
+
qemu_gluster_parse_flags(bdrv_flags, &open_flags);
s->fd = glfs_open(s->glfs, gconf->image, open_flags);
@@ -366,6 +383,16 @@ static int qemu_gluster_reopen_prepare(BDRVReopenState *state,
goto exit;
}
+#ifdef CONFIG_GLUSTERFS_XLATOR_OPT
+ ret = glfs_set_xlator_option(reop_s->glfs, "*-write-behind",
+ "resync-failed-syncs-after-fsync", "on");
+ if (ret < 0) {
+ error_setg_errno(errp, errno, "Unable to set xlator key/value pair");
+ ret = -errno;
+ goto exit;
+ }
+#endif
+
reop_s->fd = glfs_open(reop_s->glfs, gconf->image, open_flags);
if (reop_s->fd == NULL) {
/* reops->glfs will be cleaned up in _abort */
@@ -613,11 +640,35 @@ static coroutine_fn int qemu_gluster_co_flush_to_disk(BlockDriverState *bs)
ret = glfs_fsync_async(s->fd, gluster_finish_aiocb, &acb);
if (ret < 0) {
- return -errno;
+ ret = -errno;
+ goto error;
}
qemu_coroutine_yield();
+ if (acb.ret < 0) {
+ ret = acb.ret;
+ goto error;
+ }
+
return acb.ret;
+
+error:
+ /* Some versions of Gluster (3.5.6 -> 3.5.8?) will not retain its cache
+ * after a fsync failure, so we have no way of allowing the guest to safely
+ * continue. Gluster versions prior to 3.5.6 don't retain the cache
+ * either, but will invalidate the fd on error, so this is again our only
+ * option.
+ *
+ * The 'resync-failed-syncs-after-fsync' xlator option for the
+ * write-behind cache will cause later gluster versions to retain its
+ * cache after error, so long as the fd remains open. However, we
+ * currently have no way of knowing if this option is supported.
+ *
+ * TODO: Once gluster provides a way for us to determine if the option
+ * is supported, bypass the closure and setting drv to NULL. */
+ qemu_gluster_close(bs);
+ bs->drv = NULL;
+ return ret;
}
#ifdef CONFIG_GLUSTERFS_DISCARD
diff --git a/configure b/configure
index f1c307bfc6..ab54f3c8ee 100755
--- a/configure
+++ b/configure
@@ -298,6 +298,7 @@ coroutine=""
coroutine_pool=""
seccomp=""
glusterfs=""
+glusterfs_xlator_opt="no"
glusterfs_discard="no"
glusterfs_zerofill="no"
archipelago="no"
@@ -3400,6 +3401,9 @@ if test "$glusterfs" != "no" ; then
glusterfs="yes"
glusterfs_cflags=`$pkg_config --cflags glusterfs-api`
glusterfs_libs=`$pkg_config --libs glusterfs-api`
+ if $pkg_config --atleast-version=4 glusterfs-api; then
+ glusterfs_xlator_opt="yes"
+ fi
if $pkg_config --atleast-version=5 glusterfs-api; then
glusterfs_discard="yes"
fi
@@ -5342,6 +5346,10 @@ if test "$glusterfs" = "yes" ; then
echo "GLUSTERFS_LIBS=$glusterfs_libs" >> $config_host_mak
fi
+if test "$glusterfs_xlator_opt" = "yes" ; then
+ echo "CONFIG_GLUSTERFS_XLATOR_OPT=y" >> $config_host_mak
+fi
+
if test "$glusterfs_discard" = "yes" ; then
echo "CONFIG_GLUSTERFS_DISCARD=y" >> $config_host_mak
fi