From f8005451d75f4879a93b12c14b162dd60f81ec56 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Wed, 22 Feb 2017 15:41:42 -0800 Subject: tmpfs: change shmem_mapping() to test shmem_aops Callers of shmem_mapping() are interested in whether the mapping is swap backed - except for uprobes, which is interested in whether it should use shmem_read_mapping_page(). All these callers are better served by a shmem_mapping() which checks for shmem_aops, than the current version which goes through several indirections to find where the inode lives - and has the surprising effect that a private mmap of /dev/zero satisfies both vma_is_anonymous() and shmem_mapping(), when that device node is on devtmpfs. I don't think anything in the tree suffers from that surprise, but it caught me out, and is better fixed. Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1612052148530.13021@eggly.anvils Signed-off-by: Hugh Dickins Acked-by: Johannes Weiner Cc: Oleg Nesterov Cc: "Kirill A. Shutemov" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/shmem.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) (limited to 'mm/shmem.c') diff --git a/mm/shmem.c b/mm/shmem.c index 3a7587a0314d..7d52cd4b504d 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2175,10 +2175,7 @@ static struct inode *shmem_get_inode(struct super_block *sb, const struct inode bool shmem_mapping(struct address_space *mapping) { - if (!mapping->host) - return false; - - return mapping->host->i_sb->s_op == &shmem_ops; + return mapping->a_ops == &shmem_aops; } #ifdef CONFIG_TMPFS -- cgit v1.2.3