@@ -533,6 +533,9 @@ static int unlazy_walk(struct nameidata *nd, struct dentry *dentry)
struct dentry *parent = nd->path.dentry;
BUG_ON(!(nd->flags & LOOKUP_RCU));
+ if (nd->flags & LOOKUP_LINK_RCU)
+ /* Cannot unlazy in the middle of following a symlink */
+ return -ECHILD;
/*
* After legitimizing the bastards, terminate_walk()
@@ -743,7 +746,8 @@ static inline void put_link(struct nameidata *nd, struct path *link, void *cooki
struct inode *inode = link->dentry->d_inode;
if (inode->i_op->put_link)
inode->i_op->put_link(link->dentry, nd, cookie);
- path_put(link);
+ if (!(nd->flags & LOOKUP_LINK_RCU))
+ path_put(link);
}
int sysctl_protected_symlinks __read_mostly = 0;
@@ -869,9 +873,10 @@ follow_link(struct path *link, struct nameidata *nd, void **p)
int error;
char *s;
- BUG_ON(nd->flags & LOOKUP_RCU);
-
- if (link->mnt == nd->path.mnt)
+ nd->flags &= ~LOOKUP_LINK_RCU;
+ if (nd->flags & LOOKUP_RCU)
+ nd->flags |= LOOKUP_LINK_RCU;
+ else if (link->mnt == nd->path.mnt)
mntget(link->mnt);
error = -ELOOP;
@@ -921,7 +926,8 @@ follow_link(struct path *link, struct nameidata *nd, void **p)
out_put_nd_path:
*p = NULL;
terminate_walk(nd);
- path_put(link);
+ if (!(nd->flags & LOOKUP_LINK_RCU))
+ path_put(link);
return error;
}
@@ -1644,6 +1650,8 @@ static inline int nested_symlink(struct path *path, struct nameidata *nd)
current->link_count--;
nd->depth--;
+ if (!nd->depth)
+ nd->flags &= ~LOOKUP_LINK_RCU;
return res;
}
@@ -32,6 +32,7 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT, LAST_BIND};
#define LOOKUP_PARENT 0x0010
#define LOOKUP_REVAL 0x0020
#define LOOKUP_RCU 0x0040
+#define LOOKUP_LINK_RCU 0x0080
/*
* Intent data
When we support ->follow_link in RCU-walk we will not want to take a reference to the 'struct path *link' passed to follow_link, and correspondingly will not want to drop that reference. As link_path_walk will complete_walk() in the case of an error, and as complete_walk() will clear LOOKUP_RCU, we cannot test LOOKUP_RCU to determine if the path should be 'put'. So introduce a new flag: LOOKUP_LINK_RCU. This is set on entry to follow_link() if appropriate and put_link() will only call path_put() if it is clear. Also, unlazy_walk() will fail if LOOKUP_LINK_RCU is set. This is because there is no way for unlazy_walk to get references on all the "struct path *link"s that are protected by that flag. Signed-off-by: NeilBrown <neilb@suse.de> --- fs/namei.c | 18 +++++++++++++----- include/linux/namei.h | 1 + 2 files changed, 14 insertions(+), 5 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html