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vg_write: optimize caching of precommitted VG

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Every vg_write stores new 'metadata' into precommitted slot.
For this step we use 'serialized buffer' to ascii metadata.

Instead of recreating this buffer after whole 'vg_write()' we
use this buffer instantly for creating of precommitted VG.

This has also the advantage of catching any problems with
reparsing of ascii metadata back to VG early before any write.
This commit is contained in:
Zdenek Kabelac 2021-03-05 22:12:58 +01:00
parent a125a3bb50
commit bc0cb66304
2 changed files with 17 additions and 29 deletions
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17
lib/format_text/format-text.c
View File

@ -28,6 +28,7 @@
#include "lib/mm/xlate.h"
#include "lib/label/label.h"
#include "lib/cache/lvmcache.h"
#include "libdaemon/client/config-util.h"
#include <unistd.h>
#include <limits.h>
@ -579,6 +580,7 @@ static int _vg_write_raw(struct format_instance *fid, struct volume_group *vg,
struct metadata_area *mda)
{
char desc[2048];
struct dm_config_tree *cft;
struct mda_context *mdac = (struct mda_context *) mda->metadata_locn;
struct text_fid_context *fidtc = (struct text_fid_context *) fid->private;
struct raw_locn *rlocn_old;
@ -662,6 +664,21 @@ static int _vg_write_raw(struct format_instance *fid, struct volume_group *vg,
fidtc->write_buf = write_buf;
fidtc->write_buf_size = write_buf_size;
fidtc->new_metadata_size = new_size;
/* Immediatelly reuse existing buffer for parsing metadata back.
* Such VG is then used for as precommitted VG and later committed VG.
*
* 'Lazy' creation of such VG might improve performance, but we
* lose important validation that written metadata can be parsed. */
if (!(cft = config_tree_from_string_without_dup_node_check(write_buf))) {
log_error("Error parsing metadata for VG %s.", vg->name);
goto out;
}
release_vg(vg->vg_precommitted);
vg->vg_precommitted = import_vg_from_config_tree(vg->cmd, vg->fid, cft);
dm_config_destroy(cft);
if (!vg->vg_precommitted)
goto_out;
}
if (!new_size || !write_buf) {

29
lib/metadata/metadata.c
View File

@ -996,32 +996,6 @@ static void _vg_move_cached_precommitted_to_committed(struct volume_group *vg)
vg->vg_precommitted = NULL;
}
/*
* Update content of precommitted VG
*
* TODO: Optimize in the future, since lvmetad needs similar
* config tree processing in lvmetad_vg_update().
*/
static int _vg_update_embedded_copy(struct volume_group *vg, struct volume_group **vg_embedded)
{
struct dm_config_tree *cft;
_vg_wipe_cached_precommitted(vg);
/* Copy the VG using an export followed by import */
if (!(cft = export_vg_to_config_tree(vg)))
return_0;
if (!(*vg_embedded = import_vg_from_config_tree(vg->cmd, vg->fid, cft))) {
dm_config_destroy(cft);
return_0;
}
dm_config_destroy(cft);
return 1;
}
int lv_has_unknown_segments(const struct logical_volume *lv)
{
struct lv_segment *seg;
@ -3121,9 +3095,6 @@ int vg_write(struct volume_group *vg)
}
}
if (!_vg_update_embedded_copy(vg, &vg->vg_precommitted)) /* prepare precommited */
return_0;
lockd_vg_update(vg);
return 1;