[lvm-devel] [PATCH 08/38] Add mda_locn_match() internal library function for mapping pv/device to VG mda.
Dave Wysochanski
dwysocha at redhat.com
Sat Jun 26 02:52:39 UTC 2010
A metadata_area is defined independent of the location. One downside
is that there is no obvious mapping from a pv to an mda. For a PV in
a VG, we need a way to start with a PV and end up with an MDA, if we
are to manage mdas starting with a device/pv. This function provides
us a way to go down the list of PVs on a VG, and identify which ones
match a particular PV.
I'm not entirely happy with this approach, but it does fit into the
existing structures in a reasonable way.
An alternative solution might be to refactor the VG - PV interface such
that mdas are a list tied to a PV. However, this seemed a bit tricky since
a PV does not come into existence until after the list of mdas is
constructed (see _vg_read() - we create a 'fid' and attach mdas to it,
then we go through them and attach pvs).
Signed-off-by: Dave Wysochanski <dwysocha at redhat.com>
---
lib/format_text/format-text.c | 15 +++++++++++++++
lib/metadata/metadata.c | 30 ++++++++++++++++++++++++++++++
lib/metadata/metadata.h | 7 +++++++
3 files changed, 52 insertions(+), 0 deletions(-)
diff --git a/lib/format_text/format-text.c b/lib/format_text/format-text.c
index 723dfb9..901fa2d 100644
--- a/lib/format_text/format-text.c
+++ b/lib/format_text/format-text.c
@@ -121,6 +121,20 @@ static int _mda_in_vg_raw(struct format_instance *fid __attribute((unused)),
return 0;
}
+static int _mda_locn_match_raw(struct metadata_area *mda1,
+ struct metadata_area *mda2)
+{
+ struct mda_context *mda1c = (struct mda_context *) mda1->metadata_locn;
+ struct mda_context *mda2c = (struct mda_context *) mda2->metadata_locn;
+
+ if ((mda1c->area.dev == mda2c->area.dev) &&
+ (mda1c->area.start == mda2c->area.start) &&
+ (mda1c->area.size == mda2c->area.size))
+ return 1;
+
+ return 0;
+}
+
/*
* For circular region between region_start and region_start + region_size,
* back up one SECTOR_SIZE from 'region_ptr' and return the value.
@@ -1730,6 +1744,7 @@ static struct metadata_area_ops _metadata_text_raw_ops = {
.mda_total_sectors = _mda_total_sectors_raw,
.mda_in_vg = _mda_in_vg_raw,
.pv_analyze_mda = _pv_analyze_mda_raw,
+ .mda_locn_match = _mda_locn_match_raw
};
/* pvmetadatasize in sectors */
diff --git a/lib/metadata/metadata.c b/lib/metadata/metadata.c
index 9764fb7..7af3dd2 100644
--- a/lib/metadata/metadata.c
+++ b/lib/metadata/metadata.c
@@ -3855,6 +3855,36 @@ uint32_t pv_pe_alloc_count(const struct physical_volume *pv)
return pv_field(pv, pe_alloc_count);
}
+/*
+ * This function provides a way to answer the question on a format specific
+ * basis - does the format specfic context of these two metadata areas
+ * match?
+ *
+ * A metatdata_area is defined to be independent of the underlying context.
+ * This has the benefit that we can use the same abstraction to read disks
+ * (see _metadata_text_raw_ops) or files (see _metadata_text_file_ops).
+ * However, one downside is there is no format-independent way to determine
+ * whether a given metadata_area is attached to a specific device - in fact,
+ * it may not be attached to a device at all.
+ *
+ * Thus, LVM is structured such that an mda is not a member of struct
+ * physical_volume. The location of the mda depends on whether
+ * the PV is in a volume group. A PV not in a VG has an mda on the
+ * 'info->mda' list in lvmcache, while a PV in a VG has an mda on
+ * the vg->fid->metadata_areas list. For further details, see _vg_read(),
+ * and the sequence of creating the format_instance with fid->metadata_areas
+ * list, as well as the construction of the VG, with list of PVs (comes
+ * after the construction of the fid and list of mdas).
+ */
+int mda_locn_match(struct metadata_area *mda1, struct metadata_area *mda2)
+{
+ if (!mda1->ops->mda_locn_match || !mda2->ops->mda_locn_match ||
+ mda1->ops->mda_locn_match != mda2->ops->mda_locn_match)
+ return 0;
+
+ return mda1->ops->mda_locn_match(mda1, mda2);
+}
+
int mda_is_ignored(struct metadata_area *mda)
{
return (mda->flags & MDA_IGNORED);
diff --git a/lib/metadata/metadata.h b/lib/metadata/metadata.h
index 71c562a..6f6236f 100644
--- a/lib/metadata/metadata.h
+++ b/lib/metadata/metadata.h
@@ -156,6 +156,12 @@ struct metadata_area_ops {
int (*pv_analyze_mda) (const struct format_type * fmt,
struct metadata_area *mda);
+ /*
+ * Do these two metadata_areas match with respect to their underlying
+ * location?
+ */
+ int (*mda_locn_match)(struct metadata_area *mda1,
+ struct metadata_area *mda2);
};
#define MDA_IGNORED 0x00000001
@@ -169,6 +175,7 @@ struct metadata_area {
int mda_is_ignored(struct metadata_area *mda);
void mda_set_ignored(struct metadata_area *mda, int value);
+int mda_locn_match(struct metadata_area *mda1, struct metadata_area *mda2);
#define seg_pvseg(seg, s) (seg)->areas[(s)].u.pv.pvseg
#define seg_dev(seg, s) (seg)->areas[(s)].u.pv.pvseg->pv->dev
--
1.6.0.6
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