postponed directory...

diff --git a/posponed/bcache-only-permit-to-recovery-read-error-when-cache-device-is-clean.patch b/posponed/bcache-only-permit-to-recovery-read-error-when-cache-device-is-clean.patch
new file mode 100644 (file)
index 0000000..112bf74
--- /dev/null
+++ b/posponed/bcache-only-permit-to-recovery-read-error-when-cache-device-is-clean.patch
@@ -0,0 +1,76 @@
+From d59b23795933678c9638fd20c942d2b4f3cd6185 Mon Sep 17 00:00:00 2001
+From: Coly Li <colyli@suse.de>
+Date: Mon, 30 Oct 2017 14:46:31 -0700
+Subject: bcache: only permit to recovery read error when cache device is clean
+
+From: Coly Li <colyli@suse.de>
+
+commit d59b23795933678c9638fd20c942d2b4f3cd6185 upstream.
+
+When bcache does read I/Os, for example in writeback or writethrough mode,
+if a read request on cache device is failed, bcache will try to recovery
+the request by reading from cached device. If the data on cached device is
+not synced with cache device, then requester will get a stale data.
+
+For critical storage system like database, providing stale data from
+recovery may result an application level data corruption, which is
+unacceptible.
+
+With this patch, for a failed read request in writeback or writethrough
+mode, recovery a recoverable read request only happens when cache device
+is clean. That is to say, all data on cached device is up to update.
+
+For other cache modes in bcache, read request will never hit
+cached_dev_read_error(), they don't need this patch.
+
+Please note, because cache mode can be switched arbitrarily in run time, a
+writethrough mode might be switched from a writeback mode. Therefore
+checking dc->has_data in writethrough mode still makes sense.
+
+Changelog:
+V4: Fix parens error pointed by Michael Lyle.
+v3: By response from Kent Oversteet, he thinks recovering stale data is a
+    bug to fix, and option to permit it is unnecessary. So this version
+    the sysfs file is removed.
+v2: rename sysfs entry from allow_stale_data_on_failure  to
+    allow_stale_data_on_failure, and fix the confusing commit log.
+v1: initial patch posted.
+
+[small change to patch comment spelling by mlyle]
+
+Signed-off-by: Coly Li <colyli@suse.de>
+Signed-off-by: Michael Lyle <mlyle@lyle.org>
+Reported-by: Arne Wolf <awolf@lenovo.com>
+Reviewed-by: Michael Lyle <mlyle@lyle.org>
+Cc: Kent Overstreet <kent.overstreet@gmail.com>
+Cc: Nix <nix@esperi.org.uk>
+Cc: Kai Krakow <hurikhan77@gmail.com>
+Cc: Eric Wheeler <bcache@lists.ewheeler.net>
+Cc: Junhui Tang <tang.junhui@zte.com.cn>
+Signed-off-by: Jens Axboe <axboe@kernel.dk>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+
+---
+ drivers/md/bcache/request.c |   10 +++++++++-
+ 1 file changed, 9 insertions(+), 1 deletion(-)
+
+--- a/drivers/md/bcache/request.c
++++ b/drivers/md/bcache/request.c
+@@ -698,8 +698,16 @@ static void cached_dev_read_error(struct
+ {
+       struct search *s = container_of(cl, struct search, cl);
+       struct bio *bio = &s->bio.bio;
++      struct cached_dev *dc = container_of(s->d, struct cached_dev, disk);
+ 
+-      if (s->recoverable) {
++      /*
++       * If cache device is dirty (dc->has_dirty is non-zero), then
++       * recovery a failed read request from cached device may get a
++       * stale data back. So read failure recovery is only permitted
++       * when cache device is clean.
++       */
++      if (s->recoverable &&
++          (dc && !atomic_read(&dc->has_dirty))) {
+               /* Retry from the backing device: */
+               trace_bcache_read_retry(s->orig_bio);
+