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| author | Miklos Szeredi <mszeredi@redhat.com> | 2021-08-18 22:08:24 +0200 |
|---|---|---|
| committer | Miklos Szeredi <mszeredi@redhat.com> | 2021-08-18 22:08:24 +0200 |
| commit | 332f606b32b6291a944c8cf23b91f53a6e676525 (patch) | |
| tree | c3a46cae0901eec40dd900a9a64c8ad1e51647ba /include/linux/fs.h | |
| parent | 0cad6246621b5887d5b33fea84219d2a71f2f99a (diff) | |
| download | lwn-332f606b32b6291a944c8cf23b91f53a6e676525.tar.gz lwn-332f606b32b6291a944c8cf23b91f53a6e676525.zip | |
ovl: enable RCU'd ->get_acl()
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>
Diffstat (limited to 'include/linux/fs.h')
| -rw-r--r-- | include/linux/fs.h | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/include/linux/fs.h b/include/linux/fs.h index 73376dfe28d0..c6e5bcbff0c0 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -581,6 +581,11 @@ static inline void mapping_allow_writable(struct address_space *mapping) struct posix_acl; #define ACL_NOT_CACHED ((void *)(-1)) +/* + * ACL_DONT_CACHE is for stacked filesystems, that rely on underlying fs to + * cache the ACL. This also means that ->get_acl() can be called in RCU mode + * with the LOOKUP_RCU flag. + */ #define ACL_DONT_CACHE ((void *)(-3)) static inline struct posix_acl * |