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Message-Id: <1444419297-16232-3-git-send-email-lk4d4@docker.com>
Date: Fri, 9 Oct 2015 12:34:57 -0700
From: Alexander Morozov <alexandr.morozov@...ker.com>
To: Miklos Szeredi <miklos@...redi.hu>
Cc: LKML <linux-kernel@...r.kernel.org>,
Alexander Morozov <lk4d4@...ker.com>
Subject: [PATCH 2/2] fs/overlay: use same inodes for hardlinks
Fix problem with accessing hardlink to unix-socket. unix_find_other
function from net/unix/af_unix.c uses d_backing_inode helper which in
current implementation doesn't return any "backing" inode, but just
dentry->d_inode, so, there from kern_path we have path with dentry from
overlayfs and not underlying file system. Further in code in
unix_find_socket_byinode we looking for unix-socket by inode, but due
overlayfs implementation that inode for hardlink will be different from
original inode of unix-socket.
Now ovl_link doesn't create new inode, but uses old->d_inode for
instantiating new dentry. Not use inc_nlink, because nlink seems to be
correctly propagated from underlying fs where it need.
Signed-off-by: Alexander Morozov <lk4d4@...ker.com>
---
fs/overlayfs/dir.c | 25 +++++++++++++++++++------
1 file changed, 19 insertions(+), 6 deletions(-)
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index 487a157..a55c89b 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -164,8 +164,14 @@ static void ovl_dentry_update_instantiate(struct dentry *dentry,
{
ovl_dentry_version_inc(dentry->d_parent);
ovl_dentry_update(dentry, newdentry);
- ovl_copyattr(newdentry->d_inode, inode);
- d_instantiate(dentry, inode);
+ /*
+ * inode == NULL only in case of hardlink
+ * for hardlink dentry will be instantiated in ovl_link
+ */
+ if (inode) {
+ ovl_copyattr(newdentry->d_inode, inode);
+ d_instantiate(dentry, inode);
+ }
}
static int ovl_create_upper(struct dentry *dentry, struct inode *inode,
@@ -390,16 +396,19 @@ static int ovl_create_or_link(struct dentry *dentry, int mode, dev_t rdev,
const char *link, struct dentry *hardlink)
{
int err;
- struct inode *inode;
+ struct inode *inode = NULL;
struct kstat stat = {
.mode = mode,
.rdev = rdev,
};
err = -ENOMEM;
- inode = ovl_new_inode(dentry->d_sb, mode, dentry->d_fsdata);
- if (!inode)
- goto out;
+ /* We don't need inode for hardlink */
+ if (!hardlink) {
+ inode = ovl_new_inode(dentry->d_sb, mode, dentry->d_fsdata);
+ if (!inode)
+ goto out;
+ }
err = ovl_copy_up(dentry->d_parent);
if (err)
@@ -498,6 +507,10 @@ static int ovl_link(struct dentry *old, struct inode *newdir,
upper = ovl_dentry_upper(old);
err = ovl_create_or_link(new, upper->d_inode->i_mode, 0, NULL, upper);
+ if (!err) {
+ ihold(old->d_inode);
+ d_instantiate(new, old->d_inode);
+ }
out_drop_write:
ovl_drop_write(old);
--
2.6.1
--
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