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mm: convert i_mmap_mutex to rwsem

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The i_mmap_mutex is a close cousin of the anon vma lock, both protecting
similar data, one for file backed pages and the other for anon memory.  To
this end, this lock can also be a rwsem.  In addition, there are some
important opportunities to share the lock when there are no tree
modifications.

This conversion is straightforward.  For now, all users take the write
lock.

[sfr@canb.auug.org.au: update fremap.c]
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
Acked-by: "Kirill A. Shutemov" <kirill@shutemov.name>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Davidlohr Bueso 2014-12-12 16:54:24 -08:00 • committed by Linus Torvalds
parent 83cde9e8ba
commit c8c06efa8b
10 changed files with 30 additions and 29 deletions
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10
mm/hugetlb.c
View file

@ -2726,9 +2726,9 @@ void __unmap_hugepage_range_final(struct mmu_gather *tlb,
* on its way out. We're lucky that the flag has such an appropriate
* name, and can in fact be safely cleared here. We could clear it
* before the __unmap_hugepage_range above, but all that's necessary
* is to clear it before releasing the i_mmap_mutex. This works
* is to clear it before releasing the i_mmap_rwsem. This works
* because in the context this is called, the VMA is about to be
* destroyed and the i_mmap_mutex is held.
* destroyed and the i_mmap_rwsem is held.
*/
vma->vm_flags &= ~VM_MAYSHARE;
}
@ -3370,9 +3370,9 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
spin_unlock(ptl);
}
/*
* Must flush TLB before releasing i_mmap_mutex: x86's huge_pmd_unshare
* Must flush TLB before releasing i_mmap_rwsem: x86's huge_pmd_unshare
* may have cleared our pud entry and done put_page on the page table:
* once we release i_mmap_mutex, another task can do the final put_page
* once we release i_mmap_rwsem, another task can do the final put_page
* and that page table be reused and filled with junk.
*/
flush_tlb_range(vma, start, end);
@ -3525,7 +3525,7 @@ static int vma_shareable(struct vm_area_struct *vma, unsigned long addr)
* and returns the corresponding pte. While this is not necessary for the
* !shared pmd case because we can allocate the pmd later as well, it makes the
* code much cleaner. pmd allocation is essential for the shared case because
* pud has to be populated inside the same i_mmap_mutex section - otherwise
* pud has to be populated inside the same i_mmap_rwsem section - otherwise
* racing tasks could either miss the sharing (see huge_pte_offset) or select a
* bad pmd for sharing.
*/