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tmpfs: change shmem_mapping() to test shmem_aops

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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>
This commit is contained in:
Hugh Dickins 2017-02-22 15:41:42 -08:00 committed by Linus Torvalds
parent 1663f26df3
commit f8005451d7
1 changed files with 1 additions and 4 deletions
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5
mm/shmem.c
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@ -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