The patch titled
dm snapshot: tidy pe ref counting
has been added to the -mm tree. Its filename is
dm-snapshot-tidy-pe-ref-counting.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: dm snapshot: tidy pe ref counting
From: Alasdair G Kergon <agk@xxxxxxxxxx>
Rename sibling_count to ref_count and introduce get and put functions.
Signed-off-by: Alasdair G Kergon <agk@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
drivers/md/dm-snap.c | 83 +++++++++++++++++++++++------------------
1 files changed, 48 insertions(+), 35 deletions(-)
diff -puN drivers/md/dm-snap.c~dm-snapshot-tidy-pe-ref-counting drivers/md/dm-snap.c
--- a/drivers/md/dm-snap.c~dm-snapshot-tidy-pe-ref-counting
+++ a/drivers/md/dm-snap.c
@@ -59,7 +59,7 @@ struct pending_exception {
/*
* The primary pending_exception is the one that holds
- * the sibling_count and the list of origin_bios for a
+ * the ref_count and the list of origin_bios for a
* group of pending_exceptions. It is always last to get freed.
* These fields get set up when writing to the origin.
*/
@@ -72,7 +72,7 @@ struct pending_exception {
* the sibling concerned and not pe->primary_pe->snap->lock unless
* they are the same.
*/
- atomic_t sibling_count;
+ atomic_t ref_count;
/* Pointer back to snapshot context */
struct dm_snapshot *snap;
@@ -653,10 +653,46 @@ static void __invalidate_snapshot(struct
dm_table_event(s->table);
}
+static void get_pending_exception(struct pending_exception *pe)
+{
+ atomic_inc(&pe->ref_count);
+}
+
+static struct bio *put_pending_exception(struct pending_exception *pe)
+{
+ struct pending_exception *primary_pe;
+ struct bio *origin_bios = NULL;
+
+ primary_pe = pe->primary_pe;
+
+ /*
+ * If this pe is involved in a write to the origin and
+ * it is the last sibling to complete then release
+ * the bios for the original write to the origin.
+ */
+ if (primary_pe &&
+ atomic_dec_and_test(&primary_pe->ref_count))
+ origin_bios = bio_list_get(&primary_pe->origin_bios);
+
+ /*
+ * Free the pe if it's not linked to an origin write or if
+ * it's not itself a primary pe.
+ */
+ if (!primary_pe || primary_pe != pe)
+ free_pending_exception(pe);
+
+ /*
+ * Free the primary pe if nothing references it.
+ */
+ if (primary_pe && !atomic_read(&primary_pe->ref_count))
+ free_pending_exception(primary_pe);
+
+ return origin_bios;
+}
+
static void pending_complete(struct pending_exception *pe, int success)
{
struct exception *e;
- struct pending_exception *primary_pe;
struct dm_snapshot *s = pe->snap;
struct bio *origin_bios = NULL;
struct bio *snapshot_bios = NULL;
@@ -695,30 +731,7 @@ static void pending_complete(struct pend
out:
snapshot_bios = bio_list_get(&pe->snapshot_bios);
-
- primary_pe = pe->primary_pe;
-
- /*
- * If this pe is involved in a write to the origin and
- * it is the last sibling to complete then release
- * the bios for the original write to the origin.
- */
- if (primary_pe &&
- atomic_dec_and_test(&primary_pe->sibling_count))
- origin_bios = bio_list_get(&primary_pe->origin_bios);
-
- /*
- * Free the pe if it's not linked to an origin write or if
- * it's not itself a primary pe.
- */
- if (!primary_pe || primary_pe != pe)
- free_pending_exception(pe);
-
- /*
- * Free the primary pe if nothing references it.
- */
- if (primary_pe && !atomic_read(&primary_pe->sibling_count))
- free_pending_exception(primary_pe);
+ origin_bios = put_pending_exception(pe);
up_write(&s->lock);
@@ -829,7 +842,7 @@ __find_pending_exception(struct dm_snaps
bio_list_init(&pe->origin_bios);
bio_list_init(&pe->snapshot_bios);
pe->primary_pe = NULL;
- atomic_set(&pe->sibling_count, 1);
+ atomic_set(&pe->ref_count, 0);
pe->snap = s;
pe->started = 0;
@@ -838,6 +851,7 @@ __find_pending_exception(struct dm_snaps
return NULL;
}
+ get_pending_exception(pe);
insert_exception(&s->pending, &pe->e);
out:
@@ -1012,7 +1026,7 @@ static int __origin_write(struct list_he
* is already remapped in this snapshot
* and trigger an exception if not.
*
- * sibling_count is initialised to 1 so pending_complete()
+ * ref_count is initialised to 1 so pending_complete()
* won't destroy the primary_pe while we're inside this loop.
*/
e = lookup_exception(&snap->complete, chunk);
@@ -1043,8 +1057,8 @@ static int __origin_write(struct list_he
}
if (!pe->primary_pe) {
- atomic_inc(&primary_pe->sibling_count);
pe->primary_pe = primary_pe;
+ get_pending_exception(primary_pe);
}
if (!pe->started) {
@@ -1057,20 +1071,20 @@ static int __origin_write(struct list_he
}
if (!primary_pe)
- goto out;
+ return r;
/*
* If this is the first time we're processing this chunk and
- * sibling_count is now 1 it means all the pending exceptions
+ * ref_count is now 1 it means all the pending exceptions
* got completed while we were in the loop above, so it falls to
* us here to remove the primary_pe and submit any origin_bios.
*/
- if (first && atomic_dec_and_test(&primary_pe->sibling_count)) {
+ if (first && atomic_dec_and_test(&primary_pe->ref_count)) {
flush_bios(bio_list_get(&primary_pe->origin_bios));
free_pending_exception(primary_pe);
/* If we got here, pe_queue is necessarily empty. */
- goto out;
+ return r;
}
/*
@@ -1079,7 +1093,6 @@ static int __origin_write(struct list_he
list_for_each_entry_safe(pe, next_pe, &pe_queue, list)
start_copy(pe);
- out:
return r;
}
_
Patches currently in -mm which might be from agk@xxxxxxxxxx are
dm-support-ioctls-on-mapped-devices.patch
dm-linear-support-ioctls.patch
dm-mpath-support-ioctls.patch
dm-export-blkdev_driver_ioctl.patch
dm-support-ioctls-on-mapped-devices-fix-with-fake-file.patch
dm-fix-alloc_dev-error-path.patch
dm-snapshot-fix-invalidation-enomem.patch
dm-snapshot-allow-zero-chunk_size.patch
dm-snapshot-fix-metadata-error-handling.patch
dm-snapshot-make-read-and-write-exception-functions-void.patch
dm-snapshot-fix-metadata-writing-when-suspending.patch
dm-snapshot-tidy-snapshot_map.patch
dm-snapshot-tidy-pending_complete.patch
dm-snapshot-add-workqueue.patch
dm-snapshot-tidy-pe-ref-counting.patch
dm-snapshot-fix-freeing-pending-exception.patch
dm-mirror-remove-trailing-space-from-table.patch
dm-mpath-tidy-ctr.patch
dm-mpath-use-kzalloc.patch
dm-add-uevent-change-event-on-resume.patch
dm-add-debug-macro.patch
dm-table-add-target-preresume.patch
dm-crypt-add-key-msg.patch
dm-crypt-restructure-for-workqueue-change.patch
dm-crypt-restructure-write-processing.patch
dm-crypt-move-io-to-workqueue.patch
dm-crypt-use-private-biosets.patch
dm-use-private-biosets.patch
dm-extract-device-limit-setting.patch
dm-table-add-target-flush.patch
md-dm-reduce-stack-usage-with-stacked-block-devices.patch
-
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