patch "staging/lustre/osc: Revert erroneous list_for_each_entry_safe use" added to staging-next

patch "staging/lustre/osc: Revert erroneous list_for_each_entry_safe use" added to staging-next

[gregkh]

This is a note to let you know that I've just added the patch titled

    staging/lustre/osc: Revert erroneous list_for_each_entry_safe use

to my staging git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git
in the staging-next branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will also be merged in the next major kernel release
during the merge window.

If you have any questions about this process, please let me know.


>From cd15dd6ef4ea11df87f717b8b1b83aaa738ec8af Mon Sep 17 00:00:00 2001
From: Oleg Drokin <green@linuxhacker.ru>
Date: Tue, 6 Dec 2016 22:53:48 -0500
Subject: staging/lustre/osc: Revert erroneous list_for_each_entry_safe use

I have been having a lot of unexplainable crashes in osc_lru_shrink
lately that I could not see a good explanation for and then I found
this patch that slip under the radar somehow that incorrectly
converted while loop for lru list iteration into
list_for_each_entry_safe totally ignoring that in the body of
the loop we drop spinlocks guarding this list and move list entries
around.
Not sure why it was not showing up right away, perhaps some of the
more recent LRU changes committed caused some extra pressure on this
code that finally highlighted the breakage.

Reverts: 8adddc36b1fc ("staging: lustre: osc: Use list_for_each_entry_safe")
CC: Bhaktipriya Shridhar <bhaktipriya96@gmail.com>
Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Cc: stable <stable@vger.kernel.org> # 4.6+
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/staging/lustre/lustre/osc/osc_page.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/lustre/lustre/osc/osc_page.c b/drivers/staging/lustre/lustre/osc/osc_page.c
index c5129d14f69c..e356e4af08e1 100644
--- a/drivers/staging/lustre/lustre/osc/osc_page.c
+++ b/drivers/staging/lustre/lustre/osc/osc_page.c
@@ -537,7 +537,6 @@ long osc_lru_shrink(const struct lu_env *env, struct client_obd *cli,
 	struct cl_object *clobj = NULL;
 	struct cl_page **pvec;
 	struct osc_page *opg;
-	struct osc_page *temp;
 	int maxscan = 0;
 	long count = 0;
 	int index = 0;
@@ -568,7 +567,7 @@ long osc_lru_shrink(const struct lu_env *env, struct client_obd *cli,
 	if (force)
 		cli->cl_lru_reclaim++;
 	maxscan = min(target << 1, atomic_long_read(&cli->cl_lru_in_list));
-	list_for_each_entry_safe(opg, temp, &cli->cl_lru_list, ops_lru) {
+	while (!list_empty(&cli->cl_lru_list)) {
 		struct cl_page *page;
 		bool will_free = false;
 
@@ -578,6 +577,8 @@ long osc_lru_shrink(const struct lu_env *env, struct client_obd *cli,
 		if (--maxscan < 0)
 			break;
 
+		opg = list_entry(cli->cl_lru_list.next, struct osc_page,
+				 ops_lru);
 		page = opg->ops_cl.cpl_page;
 		if (lru_page_busy(cli, page)) {
 			list_move_tail(&opg->ops_lru, &cli->cl_lru_list);
-- 
2.10.2