diff options
author | Clark Williams <williams@redhat.com> | 2012-01-05 12:51:32 -0600 |
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committer | Clark Williams <williams@redhat.com> | 2012-01-05 12:51:32 -0600 |
commit | d76fe430665fac3f44ee88958713ecc524fd778d (patch) | |
tree | 00206c8b11eb2084d38eeccfe4b41f5e89fb779c /kernel/futex.c | |
parent | 63076d7f7f7f2650e5d0a4fa5dd2c412a255c237 (diff) | |
parent | 805a6af8dba5dfdd35ec35dc52ec0122400b2610 (diff) |
Merge commit 'v3.2' into rt-3.2-rt9v3.2-rt9
Diffstat (limited to 'kernel/futex.c')
-rw-r--r-- | kernel/futex.c | 28 |
1 files changed, 20 insertions, 8 deletions
diff --git a/kernel/futex.c b/kernel/futex.c index b104a3184132..2d311cdad5a6 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -314,17 +314,29 @@ again: #endif lock_page(page_head); + + /* + * If page_head->mapping is NULL, then it cannot be a PageAnon + * page; but it might be the ZERO_PAGE or in the gate area or + * in a special mapping (all cases which we are happy to fail); + * or it may have been a good file page when get_user_pages_fast + * found it, but truncated or holepunched or subjected to + * invalidate_complete_page2 before we got the page lock (also + * cases which we are happy to fail). And we hold a reference, + * so refcount care in invalidate_complete_page's remove_mapping + * prevents drop_caches from setting mapping to NULL beneath us. + * + * The case we do have to guard against is when memory pressure made + * shmem_writepage move it from filecache to swapcache beneath us: + * an unlikely race, but we do need to retry for page_head->mapping. + */ if (!page_head->mapping) { + int shmem_swizzled = PageSwapCache(page_head); unlock_page(page_head); put_page(page_head); - /* - * ZERO_PAGE pages don't have a mapping. Avoid a busy loop - * trying to find one. RW mapping would have COW'd (and thus - * have a mapping) so this page is RO and won't ever change. - */ - if ((page_head == ZERO_PAGE(address))) - return -EFAULT; - goto again; + if (shmem_swizzled) + goto again; + return -EFAULT; } /* |