[lvm-devel] [PATCH 2/6] Add devices/data_alignment_offset_detection to lvm.conf.
Mike Snitzer
snitzer at redhat.com
Thu Jul 23 02:53:03 UTC 2009
If the pvcreate --dataalignmentoffset option is not specified the start
of a PV's aligned data area will be padded with the associated
'alignment_offset' exposed in sysfs (unless
devices/data_alignment_offset_detection is disabled in lvm.conf).
Signed-off-by: Mike Snitzer <snitzer at redhat.com>
---
WHATS_NEW | 1 +
doc/example.conf | 9 +++++
lib/config/defaults.h | 1 +
lib/device/device.c | 71 +++++++++++++++++++++++++++++++++++++++++
lib/device/device.h | 3 ++
lib/format_text/format-text.c | 8 +++-
lib/metadata/metadata.c | 8 +++++
man/lvm.conf.5.in | 9 +++++-
8 files changed, 107 insertions(+), 3 deletions(-)
diff --git a/WHATS_NEW b/WHATS_NEW
index 92fed6a..8b8a749 100644
--- a/WHATS_NEW
+++ b/WHATS_NEW
@@ -1,5 +1,6 @@
Version 2.02.50 -
================================
+ Add devices/data_alignment_offset_detection to lvm.conf.
Add --dataalignmentoffset to pvcreate to pad aligned data area.
Add liblvm2app Makefile installation targets.
Add liblvm pkgconfig file.
diff --git a/doc/example.conf b/doc/example.conf
index 0682415..d52ab98 100644
--- a/doc/example.conf
+++ b/doc/example.conf
@@ -104,6 +104,15 @@ devices {
# Set to 0 for the default alignment of 64KB or page size, if larger.
data_alignment = 0
+ # By default, the start of a PV's aligned data area will be padded with
+ # the 'alignment_offset' exposed in sysfs. This offset is often 0 but
+ # may be non-zero; e.g.: certain 4KB sector drives that compensate for
+ # windows partitioning will have an alignment_offset of 3584 bytes
+ # (sector 7 is the lowest aligned logical block, the 4KB sectors start
+ # at LBA -1, and consequently sector 63 is aligned on a 4KB boundary).
+ # 1 enables; 0 disables.
+ data_alignment_offset_detection = 1
+
# If, while scanning the system for PVs, LVM2 encounters a device-mapper
# device that has its I/O suspended, it waits for it to become accessible.
# Set this to 1 to skip such devices. This should only be needed
diff --git a/lib/config/defaults.h b/lib/config/defaults.h
index ee6d758..68a862e 100644
--- a/lib/config/defaults.h
+++ b/lib/config/defaults.h
@@ -34,6 +34,7 @@
#define DEFAULT_MD_COMPONENT_DETECTION 1
#define DEFAULT_MD_CHUNK_ALIGNMENT 1
#define DEFAULT_IGNORE_SUSPENDED_DEVICES 1
+#define DEFAULT_DATA_ALIGNMENT_OFFSET_DETECTION 1
#define DEFAULT_LOCK_DIR "/var/lock/lvm"
#define DEFAULT_LOCKING_LIB "liblvm2clusterlock.so"
diff --git a/lib/device/device.c b/lib/device/device.c
index 3248dd6..ebd8141 100644
--- a/lib/device/device.c
+++ b/lib/device/device.c
@@ -282,3 +282,74 @@ int _get_partition_type(struct dev_mgr *dm, struct device *d)
return 0;
}
#endif
+
+#ifdef linux
+
+static unsigned long _dev_topology_attribute(const char *attribute,
+ const char *sysfs_dir,
+ struct device *dev)
+{
+ char path[PATH_MAX+1], buffer[64];
+ FILE *fp;
+ struct stat info;
+ unsigned long result = 0UL;
+
+ if (!attribute || !*attribute)
+ return_0;
+
+ if (!sysfs_dir || !*sysfs_dir)
+ return_0;
+
+ if (dm_snprintf(path, PATH_MAX, "%s/dev/block/%d:%d/%s",
+ sysfs_dir, (int)MAJOR(dev->dev), (int)MINOR(dev->dev),
+ attribute) < 0) {
+ log_error("dm_snprintf %s failed", attribute);
+ return 0;
+ }
+
+ /* check if the desired sysfs attribute exists */
+ if (stat(path, &info) < 0)
+ return 0;
+
+ if (!(fp = fopen(path, "r"))) {
+ log_sys_error("fopen", path);
+ return 0;
+ }
+
+ if (!fgets(buffer, sizeof(buffer), fp)) {
+ log_sys_error("fgets", path);
+ goto out;
+ }
+
+ if (sscanf(buffer, "%lu", &result) != 1) {
+ log_error("sysfs file %s not in expected format: %s", path,
+ buffer);
+ goto out;
+ }
+
+ log_very_verbose("Device %s %s is %lu bytes.",
+ dev_name(dev), attribute, result);
+
+out:
+ if (fclose(fp))
+ log_sys_error("fclose", path);
+
+ return result >> SECTOR_SHIFT;
+}
+
+unsigned long dev_alignment_offset(const char *sysfs_dir,
+ struct device *dev)
+{
+ return _dev_topology_attribute("alignment_offset",
+ sysfs_dir, dev);
+}
+
+#else
+
+unsigned long dev_alignment_offset(const char *sysfs_dir,
+ struct device *dev)
+{
+ return 0UL;
+}
+
+#endif
diff --git a/lib/device/device.h b/lib/device/device.h
index b016823..32aee41 100644
--- a/lib/device/device.h
+++ b/lib/device/device.h
@@ -100,4 +100,7 @@ unsigned long dev_md_stripe_width(const char *sysfs_dir, struct device *dev);
int is_partitioned_dev(struct device *dev);
+unsigned long dev_alignment_offset(const char *sysfs_dir,
+ struct device *dev);
+
#endif
diff --git a/lib/format_text/format-text.c b/lib/format_text/format-text.c
index 32af70b..1d2916c 100644
--- a/lib/format_text/format-text.c
+++ b/lib/format_text/format-text.c
@@ -1705,8 +1705,12 @@ static int _text_pv_setup(const struct format_type *fmt,
"%lu sectors (requested %lu sectors)",
pv_dev_name(pv), pv->pe_align, data_alignment);
- if (!pe_start)
- set_pe_align_offset(pv, data_alignment_offset);
+ if (!pe_start &&
+ (set_pe_align_offset(pv, data_alignment_offset) != data_alignment_offset) &&
+ data_alignment_offset)
+ log_warn("WARNING: %s: Overriding data alignment offset to "
+ "%lu sectors (requested %lu sectors)",
+ pv_dev_name(pv), pv->pe_align_offset, data_alignment_offset);
if (pv->pe_start < pv->pe_align) {
pv->pe_start = pv->pe_align;
diff --git a/lib/metadata/metadata.c b/lib/metadata/metadata.c
index 0dbb7bc..6ba8857 100644
--- a/lib/metadata/metadata.c
+++ b/lib/metadata/metadata.c
@@ -115,6 +115,14 @@ unsigned long set_pe_align_offset(struct physical_volume *pv,
if (!pv->dev)
goto out;
+ if (find_config_tree_bool(pv->fmt->cmd,
+ "devices/data_alignment_offset_detection",
+ DEFAULT_DATA_ALIGNMENT_OFFSET_DETECTION))
+ pv->pe_align_offset =
+ MAX(pv->pe_align_offset,
+ dev_alignment_offset(pv->fmt->cmd->sysfs_dir,
+ pv->dev));
+
log_very_verbose("%s: Setting PE alignment offset to %lu sectors.",
dev_name(pv->dev), pv->pe_align_offset);
diff --git a/man/lvm.conf.5.in b/man/lvm.conf.5.in
index 0e3a949..0e7ede4 100644
--- a/man/lvm.conf.5.in
+++ b/man/lvm.conf.5.in
@@ -142,10 +142,17 @@ when creating a new Physical Volume using the \fBlvm2\fP format.
If a Physical Volume is placed directly upon an md device and
\fBmd_chunk_alignment\fP is enabled this parameter is ignored.
Set to 0 to use the default alignment of 64KB or the page size, if larger.
+.IP
+\fBdata_alignment_offset_detection\fP \(em If set to 1, and your kernel
+provides topology information in sysfs for the Physical Volume, the
+start of the aligned data area of the Physical Volume will be padded
+with the alignment_offset exposed in sysfs.
.sp
To see the location of the first Physical Extent of an existing Physical Volume
use \fBpvs -o +pe_start\fP . It will be a multiple of the requested
-\fBdata_alignment\fP.
+\fBdata_alignment\fP plus the alignment_offset from
+\fBdata_alignment_offset_detection\fP (if enabled) or the pvcreate
+commandline.
.TP
\fBlog\fP \(em Default log settings
.IP
--
1.6.2.5
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