mm, futex: fix shared futex pgoff on shmem huge page
commit fe19bd3dae3d15d2fbfdb3de8839a6ea0fe94264 upstream. If more than one futex is placed on a shmem huge page, it can happen that waking the second wakes the first instead, and leaves the second waiting: the key's shared.pgoff is wrong. When 3.11 commit13d60f4b6a
("futex: Take hugepages into account when generating futex_key"), the only shared huge pages came from hugetlbfs, and the code added to deal with its exceptional page->index was put into hugetlb source. Then that was missed when 4.8 added shmem huge pages. page_to_pgoff() is what others use for this nowadays: except that, as currently written, it gives the right answer on hugetlbfs head, but nonsense on hugetlbfs tails. Fix that by calling hugetlbfs-specific hugetlb_basepage_index() on PageHuge tails as well as on head. Yes, it's unconventional to declare hugetlb_basepage_index() there in pagemap.h, rather than in hugetlb.h; but I do not expect anything but page_to_pgoff() ever to need it. [akpm@linux-foundation.org: give hugetlb_basepage_index() prototype the correct scope] Link: https://lkml.kernel.org/r/b17d946b-d09-326e-b42a-52884c36df32@google.com Fixes:800d8c63b2
("shmem: add huge pages support") Reported-by: Neel Natu <neelnatu@google.com> Signed-off-by: Hugh Dickins <hughd@google.com> Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org> Acked-by: Thomas Gleixner <tglx@linutronix.de> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Zhang Yi <wetpzy@gmail.com> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Darren Hart <dvhart@infradead.org> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:

committed by
Sasha Levin

parent
ab9d178167
commit
377a796e7a
@@ -35,7 +35,6 @@
|
||||
#include <linux/jhash.h>
|
||||
#include <linux/pagemap.h>
|
||||
#include <linux/syscalls.h>
|
||||
#include <linux/hugetlb.h>
|
||||
#include <linux/freezer.h>
|
||||
#include <linux/memblock.h>
|
||||
#include <linux/fault-inject.h>
|
||||
@@ -652,7 +651,7 @@ again:
|
||||
|
||||
key->both.offset |= FUT_OFF_INODE; /* inode-based key */
|
||||
key->shared.i_seq = get_inode_sequence_number(inode);
|
||||
key->shared.pgoff = basepage_index(tail);
|
||||
key->shared.pgoff = page_to_pgoff(tail);
|
||||
rcu_read_unlock();
|
||||
}
|
||||
|
||||
|
Reference in New Issue
Block a user