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53d85c9856
Currently, cleancache_register_ops returns the previous value of cleancache_ops to allow chaining. However, chaining, as it is implemented now, is extremely dangerous due to possible pool id collisions. Suppose, a new cleancache driver is registered after the previous one assigned an id to a super block. If the new driver assigns the same id to another super block, which is perfectly possible, we will have two different filesystems using the same id. No matter if the new driver implements chaining or not, we are likely to get data corruption with such a configuration eventually. This patch therefore disables the ability to override cleancache_ops altogether as potentially dangerous. If there is already cleancache driver registered, all further calls to cleancache_register_ops will return EBUSY. Since no user of cleancache implements chaining, we only need to make minor changes to the code outside the cleancache core. 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> |
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| .. | ||
| .gitignore | ||
| 00-INDEX | ||
| active_mm.txt | ||
| balance | ||
| cleancache.txt | ||
| frontswap.txt | ||
| highmem.txt | ||
| hugetlbpage.txt | ||
| hwpoison.txt | ||
| ksm.txt | ||
| numa | ||
| numa_memory_policy.txt | ||
| overcommit-accounting | ||
| page_migration | ||
| page_owner.txt | ||
| pagemap.txt | ||
| remap_file_pages.txt | ||
| slub.txt | ||
| soft-dirty.txt | ||
| split_page_table_lock | ||
| transhuge.txt | ||
| unevictable-lru.txt | ||
| zswap.txt | ||