From: Milan Broz <mbroz@redhat.com>
When processing the second part of a split bio resubmitted to the same
device we should skip the bookkeeping and avoid requesting io_lock
recursively. Also fix a possible deadlock if the wait loop gets
interrupted.
Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
---
drivers/md/dm.c | 25 +++++++++++++++++++++----
1 files changed, 21 insertions(+), 4 deletions(-)
Index: current-quilt/drivers/md/dm.c
===================================================================
--- current-quilt.orig/drivers/md/dm.c 2007-07-25 21:04:54.000000000 +0100
+++ current-quilt/drivers/md/dm.c 2007-07-25 21:04:55.000000000 +0100
@@ -564,6 +564,12 @@ static int clone2_endio(struct bio *bio,
return error;
}
+static int is_clone2(struct mapped_device *md, struct bio *bio)
+{
+ return (bio->bi_end_io == clone2_endio &&
+ bio->bi_private == md);
+}
+
static sector_t max_io_len(struct mapped_device *md,
sector_t sector, struct dm_target *ti)
{
@@ -817,6 +823,15 @@ static int dm_request(request_queue_t *q
return 0;
}
+ /*
+ * If this is the second part of a split bio,
+ * always map it immediately.
+ */
+ if (is_clone2(md, bio)) {
+ r = __split_bio(md, bio);
+ goto out_req;
+ }
+
down_read(&md->io_lock);
disk_stat_inc(dm_disk(md), ios[rw]);
@@ -1265,10 +1280,11 @@ EXPORT_SYMBOL_GPL(dm_put);
/*
* Process the deferred bios
*/
-static void __flush_deferred_io(struct mapped_device *md, struct bio *c)
+static void flush_deferred_io(struct mapped_device *md, struct bio *c)
{
struct bio *n;
+ down_read(&md->io_lock);
while (c) {
n = c->bi_next;
c->bi_next = NULL;
@@ -1276,6 +1292,7 @@ static void __flush_deferred_io(struct m
bio_io_error(c, c->bi_size);
c = n;
}
+ up_read(&md->io_lock);
}
/*
@@ -1436,8 +1453,8 @@ int dm_suspend(struct mapped_device *md,
if (atomic_read(&md->pending)) {
clear_bit(DMF_BLOCK_IO, &md->flags);
def = bio_list_get(&md->deferred);
- __flush_deferred_io(md, def);
up_write(&md->io_lock);
+ flush_deferred_io(md, def);
unlock_fs(md);
goto out; /* pushback list is already flushed, so skip flush */
}
@@ -1464,8 +1481,8 @@ flush_and_out:
spin_unlock_irqrestore(&md->pushback_lock, flags);
def = bio_list_get(&md->deferred);
- __flush_deferred_io(md, def);
up_write(&md->io_lock);
+ flush_deferred_io(md, def);
}
out:
@@ -1503,8 +1520,8 @@ int dm_resume(struct mapped_device *md)
clear_bit(DMF_BLOCK_IO, &md->flags);
def = bio_list_get(&md->deferred);
- __flush_deferred_io(md, def);
up_write(&md->io_lock);
+ flush_deferred_io(md, def);
unlock_fs(md);