This is a note to let you know that I've just added the patch titled
dm thin: grab a virtual cell before looking up the mapping
to the 3.17-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
dm-thin-grab-a-virtual-cell-before-looking-up-the-mapping.patch
and it can be found in the queue-3.17 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From c822ed967cba38505713d59ed40a114386ef6c01 Mon Sep 17 00:00:00 2001
From: Joe Thornber <ejt@xxxxxxxxxx>
Date: Fri, 10 Oct 2014 09:41:09 +0100
Subject: dm thin: grab a virtual cell before looking up the mapping
From: Joe Thornber <ejt@xxxxxxxxxx>
commit c822ed967cba38505713d59ed40a114386ef6c01 upstream.
Avoids normal IO racing with discard.
Signed-off-by: Joe Thornber <ejt@xxxxxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/md/dm-thin.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -1936,6 +1936,14 @@ static int thin_bio_map(struct dm_target
return DM_MAPIO_SUBMITTED;
}
+ /*
+ * We must hold the virtual cell before doing the lookup, otherwise
+ * there's a race with discard.
+ */
+ build_virtual_key(tc->td, block, &key);
+ if (dm_bio_detain(tc->pool->prison, &key, bio, &cell1, &cell_result))
+ return DM_MAPIO_SUBMITTED;
+
r = dm_thin_find_block(td, block, 0, &result);
/*
@@ -1959,13 +1967,10 @@ static int thin_bio_map(struct dm_target
* shared flag will be set in their case.
*/
thin_defer_bio(tc, bio);
+ cell_defer_no_holder_no_free(tc, &cell1);
return DM_MAPIO_SUBMITTED;
}
- build_virtual_key(tc->td, block, &key);
- if (dm_bio_detain(tc->pool->prison, &key, bio, &cell1, &cell_result))
- return DM_MAPIO_SUBMITTED;
-
build_data_key(tc->td, result.block, &key);
if (dm_bio_detain(tc->pool->prison, &key, bio, &cell2, &cell_result)) {
cell_defer_no_holder_no_free(tc, &cell1);
@@ -1986,6 +1991,7 @@ static int thin_bio_map(struct dm_target
* of doing so.
*/
handle_unserviceable_bio(tc->pool, bio);
+ cell_defer_no_holder_no_free(tc, &cell1);
return DM_MAPIO_SUBMITTED;
}
/* fall through */
@@ -1996,6 +2002,7 @@ static int thin_bio_map(struct dm_target
* provide the hint to load the metadata into cache.
*/
thin_defer_bio(tc, bio);
+ cell_defer_no_holder_no_free(tc, &cell1);
return DM_MAPIO_SUBMITTED;
default:
@@ -2005,6 +2012,7 @@ static int thin_bio_map(struct dm_target
* pool is switched to fail-io mode.
*/
bio_io_error(bio);
+ cell_defer_no_holder_no_free(tc, &cell1);
return DM_MAPIO_SUBMITTED;
}
}
Patches currently in stable-queue which might be from ejt@xxxxxxxxxx are
queue-3.17/dm-thin-grab-a-virtual-cell-before-looking-up-the-mapping.patch
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