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 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.
Signed-off-by: Jeff Cody <jc...@redhat.com> --- block/gluster.c | 27 +++++++++++++++++++++++++++ configure | 8 ++++++++ 2 files changed, 35 insertions(+) diff --git a/block/gluster.c b/block/gluster.c index 30a827e..b1cf71b 100644 --- a/block/gluster.c +++ b/block/gluster.c @@ -330,6 +330,23 @@ 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); @@ -386,6 +403,16 @@ 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 */ diff --git a/configure b/configure index 5db29f0..3e921fe 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" @@ -3397,6 +3398,9 @@ 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 $pkg_config --atleast-version=5 glusterfs-api; then glusterfs_discard="yes" fi @@ -5339,6 +5343,10 @@ if test "$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 -- 1.9.3