Messages in this thread Patch in this message | | | From | Yigal Korman <> | Subject | [PATCH] mm, dax: fix DAX deadlocks (COW fault) | Date | Mon, 16 Nov 2015 14:09:15 +0200 |
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DAX handling of COW faults has wrong locking sequence: dax_fault does i_mmap_lock_read do_cow_fault does i_mmap_unlock_write
Ross's commit[1] missed a fix[2] that Kirill added to Matthew's commit[3].
Original COW locking logic was introduced by Matthew here[4].
This should be applied to v4.3 as well.
[1] 0f90cc6609c7 mm, dax: fix DAX deadlocks [2] 52a2b53ffde6 mm, dax: use i_mmap_unlock_write() in do_cow_fault() [3] 843172978bb9 dax: fix race between simultaneous faults [4] 2e4cdab0584f mm: allow page fault handlers to perform the COW
Signed-off-by: Yigal Korman <yigal@plexistor.com>
Cc: Stable Tree <stable@vger.kernel.org> Cc: Boaz Harrosh <boaz@plexistor.com> Cc: Ross Zwisler <ross.zwisler@linux.intel.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Chinner <dchinner@redhat.com> Cc: Jan Kara <jack@suse.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Matthew Wilcox <matthew.r.wilcox@intel.com> --- mm/memory.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/mm/memory.c b/mm/memory.c index c716913..e5071af 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3015,9 +3015,9 @@ static int do_cow_fault(struct mm_struct *mm, struct vm_area_struct *vma, } else { /* * The fault handler has no page to lock, so it holds - * i_mmap_lock for write to protect against truncate. + * i_mmap_lock for read to protect against truncate. */ - i_mmap_unlock_write(vma->vm_file->f_mapping); + i_mmap_unlock_read(vma->vm_file->f_mapping); } goto uncharge_out; } @@ -3031,9 +3031,9 @@ static int do_cow_fault(struct mm_struct *mm, struct vm_area_struct *vma, } else { /* * The fault handler has no page to lock, so it holds - * i_mmap_lock for write to protect against truncate. + * i_mmap_lock for read to protect against truncate. */ - i_mmap_unlock_write(vma->vm_file->f_mapping); + i_mmap_unlock_read(vma->vm_file->f_mapping); } return ret; uncharge_out: -- 1.9.3
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