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format_text: Round size written up to multiple of 4096.

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Zero-fill metadata up to the next 4096 boundary then write out a
multiple of 4096 bytes to avoid triggering a read-modify-write.
This commit is contained in:
Alasdair G Kergon 2017-12-12 22:52:22 +00:00
parent 78ffa44fc5
commit 3edc25dbdf
4 changed files with 34 additions and 10 deletions
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1
WHATS_NEW
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@ -1,5 +1,6 @@
Version 2.02.177 - Version 2.02.177 -
==================================== ====================================
When writing text metadata content, use complete 4096 byte blocks.
Change text format metadata alignment from 512 to 4096 bytes. Change text format metadata alignment from 512 to 4096 bytes.
When writing metadata, consistently skip mdas marked as failed. When writing metadata, consistently skip mdas marked as failed.
Refactor and adjust text format metadata alignment calculation. Refactor and adjust text format metadata alignment calculation.

8
lib/format_text/export.c
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@ -23,6 +23,7 @@
#include "lvm-version.h" #include "lvm-version.h"
#include "toolcontext.h" #include "toolcontext.h"
#include "config-util.h" #include "config-util.h"
#include "layout.h"
#include <stdarg.h> #include <stdarg.h>
#include <time.h> #include <time.h>
@ -1079,7 +1080,12 @@ size_t text_vg_export_raw(struct volume_group *vg, const char *desc, char **buf)
goto_out; goto_out;
} }
r = f->data.buf.used + 1; f->data.buf.used += 1; /* Terminating NUL */
/* Zero fill up to next alignment boundary */
memset(f->data.buf.start + f->data.buf.used, 0, MDA_ALIGNMENT - f->data.buf.used % MDA_ALIGNMENT);
r = f->data.buf.used;
*buf = f->data.buf.start; *buf = f->data.buf.start;
out: out:

34
lib/format_text/format-text.c
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@ -704,11 +704,12 @@ static int _vg_write_raw(struct format_instance *fid, struct volume_group *vg,
struct mda_header *mdah; struct mda_header *mdah;
struct pv_list *pvl; struct pv_list *pvl;
int r = 0; int r = 0;
uint64_t new_wrap; /* Number of bytes of new metadata that wrap around to start of buffer */ uint64_t new_wrap = 0; /* Number of bytes of new metadata that wrap around to start of buffer */
uint64_t alignment = MDA_ALIGNMENT; uint64_t alignment = MDA_ALIGNMENT;
int found = 0; int found = 0;
int noprecommit = 0; int noprecommit = 0;
const char *old_vg_name = NULL; const char *old_vg_name = NULL;
uint64_t new_size_rounded;
/* Ignore any mda on a PV outside the VG. vgsplit relies on this */ /* Ignore any mda on a PV outside the VG. vgsplit relies on this */
dm_list_iterate_items(pvl, &vg->pvs) { dm_list_iterate_items(pvl, &vg->pvs) {
@ -735,6 +736,7 @@ static int _vg_write_raw(struct format_instance *fid, struct volume_group *vg,
if (!(mdah = raw_read_mda_header(fid->fmt, &mdac->area, mda_is_primary(mda)))) if (!(mdah = raw_read_mda_header(fid->fmt, &mdac->area, mda_is_primary(mda))))
goto_out; goto_out;
/* Following space is zero-filled up to the next MDA_ALIGNMENT boundary */
if (!fidtc->raw_metadata_buf && if (!fidtc->raw_metadata_buf &&
!(fidtc->raw_metadata_buf_size = !(fidtc->raw_metadata_buf_size =
text_vg_export_raw(vg, "", &fidtc->raw_metadata_buf))) { text_vg_export_raw(vg, "", &fidtc->raw_metadata_buf))) {
@ -775,19 +777,33 @@ static int _vg_write_raw(struct format_instance *fid, struct volume_group *vg,
vg->name, dev_name(mdac->area.dev), mdac->rlocn.size, mdah->size - MDA_HEADER_SIZE, rlocn ? rlocn->size : 0); vg->name, dev_name(mdac->area.dev), mdac->rlocn.size, mdah->size - MDA_HEADER_SIZE, rlocn ? rlocn->size : 0);
goto out; goto out;
} }
new_size_rounded = mdac->rlocn.size;
} else {
/* Round up to a multiple of the new alignment */
if (mdac->rlocn.offset + new_size_rounded < mdah->size)
new_size_rounded = (mdac->rlocn.size | (alignment - 1)) + 1;
else
new_size_rounded = mdac->rlocn.size;
} }
log_debug_metadata("Writing %s metadata to %s at " FMTu64 " len " FMTu64 " of " FMTu64 " aligned to " FMTu64, log_debug_metadata("Writing %s metadata to %s at " FMTu64 " len " FMTu64 " (rounded to " FMTu64 ") of " FMTu64 " aligned to " FMTu64,
vg->name, dev_name(mdac->area.dev), mdac->area.start + vg->name, dev_name(mdac->area.dev), mdac->area.start +
mdac->rlocn.offset, mdac->rlocn.size - new_wrap, mdac->rlocn.size, alignment); mdac->rlocn.offset, mdac->rlocn.size - new_wrap, new_size_rounded, mdac->rlocn.size, alignment);
/* Write text out, circularly */ if (!new_wrap) {
if (!dev_write(mdac->area.dev, mdac->area.start + mdac->rlocn.offset, /* Write text out, in alignment-sized blocks */
(size_t) (mdac->rlocn.size - new_wrap), MDA_CONTENT_REASON(mda_is_primary(mda)), if (!dev_write(mdac->area.dev, mdac->area.start + mdac->rlocn.offset,
fidtc->raw_metadata_buf)) (size_t) new_size_rounded, MDA_CONTENT_REASON(mda_is_primary(mda)),
goto_out; fidtc->raw_metadata_buf))
goto_out;
} else {
/* Write text out, circularly */
if (!dev_write(mdac->area.dev, mdac->area.start + mdac->rlocn.offset,
(size_t) (mdac->rlocn.size - new_wrap), MDA_CONTENT_REASON(mda_is_primary(mda)),
fidtc->raw_metadata_buf))
goto_out;
if (new_wrap) {
log_debug_metadata("Writing wrapped metadata to %s at " FMTu64 " len " FMTu64 " of " FMTu64, log_debug_metadata("Writing wrapped metadata to %s at " FMTu64 " len " FMTu64 " of " FMTu64,
dev_name(mdac->area.dev), mdac->area.start + dev_name(mdac->area.dev), mdac->area.start +
MDA_HEADER_SIZE, new_wrap, mdac->rlocn.size); MDA_HEADER_SIZE, new_wrap, mdac->rlocn.size);

1
lib/format_text/layout.h
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@ -17,6 +17,7 @@
#define _LVM_TEXT_LAYOUT_H #define _LVM_TEXT_LAYOUT_H
#include "config.h" #include "config.h"
#include "format-text.h"
#include "metadata.h" #include "metadata.h"
#include "lvmcache.h" #include "lvmcache.h"
#include "uuid.h" #include "uuid.h"