From: Yigal Korman Date: Mon, 16 Nov 2015 12:09:15 +0000 (+0200) Subject: mm, dax: fix DAX deadlocks (COW fault) X-Git-Tag: v4.1.12-92~18^2^2~59 X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=631ac13d12dfd73bee3526a7d2d2673ce50ca82f;p=users%2Fjedix%2Flinux-maple.git mm, dax: fix DAX deadlocks (COW fault) Orabug: 22913653 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 Cc: Cc: Boaz Harrosh Cc: Alexander Viro Cc: Dave Chinner Cc: Jan Kara Cc: "Kirill A. Shutemov" Cc: Matthew Wilcox Acked-by: Ross Zwisler Signed-off-by: Yigal Korman Signed-off-by: Dan Williams (cherry picked from commit 0df9d41ab5d43dc5b20abc8b22a6b6d098b03994) Signed-off-by: Dan Duval --- diff --git a/mm/memory.c b/mm/memory.c index fd0c3aa4c259..0a85c3498f81 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2997,9 +2997,9 @@ 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; } @@ -3013,9 +3013,9 @@ 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: