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authorTejun Heo <tj@kernel.org>2015-09-23 17:07:29 -0400
committerTejun Heo <tj@kernel.org>2015-09-24 16:48:52 -0400
commit9badce000e2ce68ba74838a3cd356dde58221c2f (patch)
treee23ec4dbe5b23e420ab0138dde80382b544df876 /include
parent0c986253b939cc14c69d4adbe2b4121bdf4aa220 (diff)
downloadlinux-linaro-stable-9badce000e2ce68ba74838a3cd356dde58221c2f.tar.gz
cgroup, writeback: don't enable cgroup writeback on traditional hierarchies
inode_cgwb_enabled() gates cgroup writeback support. If it returns true, each inode is attached to the corresponding memory domain which gets mapped to io domain. It currently only tests whether the filesystem and bdi support cgroup writeback; however, cgroup writeback support doesn't work on traditional hierarchies and thus it should also test whether memcg and iocg are on the default hierarchy. This caused traditional hierarchy setups to hit the cgroup writeback path inadvertently and ended up creating separate writeback domains for each memcg and mapping them all to the root iocg uncovering a couple issues in the cgroup writeback path. cgroup writeback was never meant to be enabled on traditional hierarchies. Make inode_cgwb_enabled() test whether both memcg and iocg are on the default hierarchy. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Artem Bityutskiy <dedekind1@gmail.com> Reported-by: Dexuan Cui <decui@microsoft.com> Link: http://lkml.kernel.org/g/1443012552.19983.209.camel@gmail.com Link: http://lkml.kernel.org/g/f30d4a6aa8a546ff88f73021d026a453@SIXPR30MB031.064d.mgd.msft.net
Diffstat (limited to 'include')
-rw-r--r--include/linux/backing-dev.h11
1 files changed, 9 insertions, 2 deletions
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 5a5d79ee256f..d5eb4ad1c534 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -13,6 +13,7 @@
#include <linux/sched.h>
#include <linux/blkdev.h>
#include <linux/writeback.h>
+#include <linux/memcontrol.h>
#include <linux/blk-cgroup.h>
#include <linux/backing-dev-defs.h>
#include <linux/slab.h>
@@ -252,13 +253,19 @@ int inode_congested(struct inode *inode, int cong_bits);
* @inode: inode of interest
*
* cgroup writeback requires support from both the bdi and filesystem.
- * Test whether @inode has both.
+ * Also, both memcg and iocg have to be on the default hierarchy. Test
+ * whether all conditions are met.
+ *
+ * Note that the test result may change dynamically on the same inode
+ * depending on how memcg and iocg are configured.
*/
static inline bool inode_cgwb_enabled(struct inode *inode)
{
struct backing_dev_info *bdi = inode_to_bdi(inode);
- return bdi_cap_account_dirty(bdi) &&
+ return cgroup_on_dfl(mem_cgroup_root_css->cgroup) &&
+ cgroup_on_dfl(blkcg_root_css->cgroup) &&
+ bdi_cap_account_dirty(bdi) &&
(bdi->capabilities & BDI_CAP_CGROUP_WRITEBACK) &&
(inode->i_sb->s_iflags & SB_I_CGROUPWB);
}