ovl: enable RCU'd ->get_acl()

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Overlayfs does not cache ACL's (to avoid double caching).  Instead it just
calls the underlying filesystem's i_op->get_acl(), which will return the
cached value, if possible.

In rcu path walk, however, get_cached_acl_rcu() is employed to get the
value from the cache, which will fail on overlayfs resulting in dropping
out of rcu walk mode.  This can result in a big performance hit in certain
situations.

Fix by calling ->get_acl() with rcu=true in case of ACL_DONT_CACHE (which
indicates pass-through)

Reported-by: garyhuang <zjh.20052005@163.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

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This commit is contained in:

Miklos Szeredi 2021-08-18 22:08:24 +02:00

parent 0cad624662

commit 332f606b32

4 changed files with 23 additions and 5 deletions

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7

fs/overlayfs/inode.c

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13

fs/posix_acl.c

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5

include/linux/fs.h

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3

include/linux/posix_acl.h

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