fs, mm: account filp cache to kmemcg

shakeelb · torvalds · commit f3f7c0935578 · 2017-11-15T18:21:04.000-08:00
The allocations from filp cache can be directly triggered by userspace applications. A buggy application can consume a significant amount of unaccounted system memory. Though we have not noticed such buggy applications in our production but upon close inspection, we found that a lot of machines spend very significant amount of memory on these caches. One way to limit allocations from filp cache is to set system level limit of maximum number of open files. However this limit is shared between different users on the system and one user can hog this resource. To cater that, we can charge filp to kmemcg and set the maximum limit very high and let the memory limit of each user limit the number of files they can open and indirectly limiting their allocations from filp cache. One side effect of this change is that it will allow _sysctl() to return ENOMEM and the man page of _sysctl() does not specify that. However the man page also discourages to use _sysctl() at all. Link: http://lkml.kernel.org/r/20171011190359.34926-1-shakeelb@google.com Signed-off-by: Shakeel Butt <shakeelb@google.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Greg Thelen <gthelen@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/file_table.c b/fs/file_table.c
@@ -312,7 +312,7 @@ void put_filp(struct file *file)
 void __init files_init(void)
 {
 	filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,
-			SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
+			SLAB_HWCACHE_ALIGN | SLAB_PANIC | SLAB_ACCOUNT, NULL);
 	percpu_counter_init(&nr_files, 0, GFP_KERNEL);
 }
 

Original file line number	Diff line number	Diff line change
`@@ -312,7 +312,7 @@ void put_filp(struct file *file)`
`312`	`312`	`void __init files_init(void)`
`313`	`313`	`{`
`314`	`314`	`filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,`
`315`		`- SLAB_HWCACHE_ALIGN \| SLAB_PANIC, NULL);`
	`315`	`+ SLAB_HWCACHE_ALIGN \| SLAB_PANIC \| SLAB_ACCOUNT, NULL);`
`316`	`316`	`percpu_counter_init(&nr_files, 0, GFP_KERNEL);`
`317`	`317`	`}`
`318`	`318`