The commit is pushed to "branch-rh7-3.10.0-123.1.2-ovz" and will appear at
https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-123.1.2.vz7.5.13
------>
commit 73997df7ea94fc95b7b0db70fbacc1c791a89acb
Author: Vladimir Davydov <vdavy...@parallels.com>
Date: Tue Jun 16 19:14:09 2015 +0400
ub/fs: access dirtied_ub under rcu lock in __writeback_single_inode
Related to patchset:
https://jira.sw.ru/browse/PSBM-34007
Vladimir Davydov (7):
ioprio: move IOPRIO_WHO_UBC handling out of rcu section
ub: zap ub_{init,fini}_ioprio
ub: export ub_get_{mem,blkio}_css
ub: ressurrect ioprio_set IOPRIO_WHO_UBC
ub: ressurrect iostat and ioprio reporting
ub: account writeback io
ub: do not include block/blk-cgroup.h from io_prio.c
This patch description:
Unlike RH6, we are not holding any locks in __writeback_single_inode, so
we must dereference dirtied_ub carefully, under rcu read lock.
Also, if dirtied_ub == NULL, account writeback to ub0 as suggested by
dmonakhov@.
Signed-off-by: Vladimir Davydov <vdavy...@parallels.com>
---
fs/fs-writeback.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 8362cc9..b2f77f4 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -491,16 +491,18 @@ __do_writeback_single_inode(struct inode *inode, struct
writeback_control *wbc)
static int
__writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
{
- struct user_beancounter *ub = inode->i_mapping->dirtied_ub;
+ struct user_beancounter *ub;
int ret;
- if (likely(get_exec_ub() == ub || !ub))
- return __do_writeback_single_inode(inode, wbc);
+ rcu_read_lock();
+ ub = rcu_dereference(inode->i_mapping->dirtied_ub);
+ if (!ub || !get_beancounter_rcu(ub))
+ ub = get_beancounter(get_ub0());
+ rcu_read_unlock();
- ub = get_beancounter_rcu(ub) ? set_exec_ub(ub) : NULL;
+ ub = set_exec_ub(ub);
ret = __do_writeback_single_inode(inode, wbc);
- if (ub)
- put_beancounter(set_exec_ub(ub));
+ put_beancounter(set_exec_ub(ub));
return ret;
}
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