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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 /fs/posix_acl.c | |
| 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 'fs/posix_acl.c')
| -rw-r--r-- | fs/posix_acl.c | 13 |
1 files changed, 12 insertions, 1 deletions
diff --git a/fs/posix_acl.c b/fs/posix_acl.c index 4f1ef826e040..f5c25f580dd9 100644 --- a/fs/posix_acl.c +++ b/fs/posix_acl.c @@ -22,6 +22,7 @@ #include <linux/xattr.h> #include <linux/export.h> #include <linux/user_namespace.h> +#include <linux/namei.h> static struct posix_acl **acl_by_type(struct inode *inode, int type) { @@ -56,7 +57,17 @@ EXPORT_SYMBOL(get_cached_acl); struct posix_acl *get_cached_acl_rcu(struct inode *inode, int type) { - return rcu_dereference(*acl_by_type(inode, type)); + struct posix_acl *acl = rcu_dereference(*acl_by_type(inode, type)); + + if (acl == ACL_DONT_CACHE) { + struct posix_acl *ret; + + ret = inode->i_op->get_acl(inode, type, LOOKUP_RCU); + if (!IS_ERR(ret)) + acl = ret; + } + + return acl; } EXPORT_SYMBOL(get_cached_acl_rcu); |