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authorHugh Dickins <hughd@google.com>2017-02-22 15:41:42 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2017-02-22 16:41:27 -0800
commitf8005451d75f4879a93b12c14b162dd60f81ec56 (patch)
tree59ea91b6fd31565cdcd424249172bfea1852c0d0
parent1663f26df3df7df3720306ca67f5ea8296d68fa1 (diff)
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 <hughd@google.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/shmem.c5
1 files changed, 1 insertions, 4 deletions
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

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