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Subject[PATCH 05/16] vfs: make follow_link check RCU safe
Date
From: Miklos Szeredi <mszeredi@suse.cz>

This will allow this code to be used in RCU mode.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
---
fs/namei.c | 12 ++++++++++--
1 files changed, 10 insertions(+), 2 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c
index f21ddb3..a3a0fa1 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2203,6 +2203,7 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
int acc_mode = op->acc_mode;
struct file *filp;
struct inode *inode;
+ int symlink_ok = 0;
int error;

nd->flags &= ~LOOKUP_PARENT;
@@ -2234,7 +2235,6 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
}

if (!(open_flag & O_CREAT)) {
- int symlink_ok = 0;
if (nd->last.name[nd->last.len])
nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
if (open_flag & O_PATH && !(nd->flags & LOOKUP_FOLLOW))
@@ -2365,8 +2365,16 @@ static struct file *do_last(struct nameidata *nd, struct path *path,
if (!inode)
goto exit_dput;

- if (inode->i_op->follow_link)
+ if (should_follow_link(inode, !symlink_ok)) {
+ if (nd->flags & LOOKUP_RCU) {
+ if (unlikely(unlazy_walk(nd, path->dentry))) {
+ error = -ECHILD;
+ goto exit;
+ }
+ }
+ BUG_ON(inode != path->dentry->d_inode);
return NULL;
+ }

path_to_nameidata(path, nd);
nd->inode = inode;
--
1.7.7


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