From 062326abd6b2983ca24c202d5409bbfd0096bf0f Mon Sep 17 00:00:00 2001 From: Greg Kroah-Hartman Date: Tue, 28 Nov 2017 10:04:53 +0100 Subject: [PATCH] postponed directory... --- ...ead-error-when-cache-device-is-clean.patch | 76 +++++++++++++++++++ 1 file changed, 76 insertions(+) create mode 100644 posponed/bcache-only-permit-to-recovery-read-error-when-cache-device-is-clean.patch 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 index 00000000000..112bf749588 --- /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 +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 + +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 +Signed-off-by: Michael Lyle +Reported-by: Arne Wolf +Reviewed-by: Michael Lyle +Cc: Kent Overstreet +Cc: Nix +Cc: Kai Krakow +Cc: Eric Wheeler +Cc: Junhui Tang +Signed-off-by: Jens Axboe +Signed-off-by: Greg Kroah-Hartman + +--- + 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); + -- 2.47.3