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authorVladimir Davydov <vdavydov@parallels.com>2015-04-14 15:46:48 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-04-14 16:49:03 -0700
commit3cb29d11174f29b76addcba4374884b14f8ea4b1 (patch)
treed73223beced01147ddeebf3a78ccc6ab4f8ffe15 /fs/super.c
parent53d85c98566535d7bc69470f008d7dcb09a0fec9 (diff)
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cleancache: remove limit on the number of cleancache enabled filesystems
The limit equals 32 and is imposed by the number of entries in the fs_poolid_map and shared_fs_poolid_map. Nowadays it is insufficient, because with containers on board a Linux host can have hundreds of active fs mounts. These maps were introduced by commit 49a9ab815acb8 ("mm: cleancache: lazy initialization to allow tmem backends to build/run as modules") in order to allow compiling cleancache drivers as modules. Real pool ids are stored in these maps while super_block->cleancache_poolid points to an entry in the map, so that on cleancache registration we can walk over all (if there are <= 32 of them, of course) cleancache-enabled super blocks and assign real pool ids. Actually, there is absolutely no need in these maps, because we can iterate over all super blocks immediately using iterate_supers. This is not racy, because cleancache_init_ops is called from mount_fs with super_block->s_umount held for writing, while iterate_supers takes this semaphore for reading, so if we call iterate_supers after setting cleancache_ops, all super blocks that had been created before cleancache_register_ops was called will be assigned pool ids by the action function of iterate_supers while all newer super blocks will receive it in cleancache_init_fs. This patch therefore removes the maps and hence the artificial limit on the number of cleancache enabled filesystems. Signed-off-by: Vladimir Davydov <vdavydov@parallels.com> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: David Vrabel <david.vrabel@citrix.com> Cc: Mark Fasheh <mfasheh@suse.com> Cc: Joel Becker <jlbec@evilplan.org> Cc: Stefan Hengelein <ilendir@googlemail.com> Cc: Florian Schmaus <fschmaus@gmail.com> Cc: Andor Daam <andor.daam@googlemail.com> Cc: Dan Magenheimer <dan.magenheimer@oracle.com> Cc: Bob Liu <lliubbo@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/super.c')
-rw-r--r--fs/super.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/super.c b/fs/super.c
index 2b7dc90ccdbb..928c20f47af9 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -224,7 +224,7 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags)
s->s_maxbytes = MAX_NON_LFS;
s->s_op = &default_op;
s->s_time_gran = 1000000000;
- s->cleancache_poolid = -1;
+ s->cleancache_poolid = CLEANCACHE_NO_POOL;
s->s_shrink.seeks = DEFAULT_SEEKS;
s->s_shrink.scan_objects = super_cache_scan;