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Message-Id: <1198874589904-git-send-email-ezk@cs.sunysb.edu>
Date: Fri, 28 Dec 2007 15:42:42 -0500
From: Erez Zadok <ezk@...sunysb.edu>
To: akpm@...ux-foundation.org
Cc: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
viro@....linux.org.uk, hch@...radead.org,
Erez Zadok <ezk@...sunysb.edu>
Subject: [PATCH 08/30] Unionfs: create new symlinks only in first branch
When creating a new symlink, always create it in the first branch, which is
always writeable, not in the branch which may have a whiteout in it. This
makes the policy for the creation of new symlinks consistent with that of
new files/directories, as well as improves efficiency a bit.
Signed-off-by: Erez Zadok <ezk@...sunysb.edu>
---
fs/unionfs/inode.c | 210 +++++++++++++++++++++++----------------------------
1 files changed, 95 insertions(+), 115 deletions(-)
diff --git a/fs/unionfs/inode.c b/fs/unionfs/inode.c
index 8076d0b..78cdfa2 100644
--- a/fs/unionfs/inode.c
+++ b/fs/unionfs/inode.c
@@ -368,16 +368,16 @@ out:
return err;
}
-static int unionfs_symlink(struct inode *dir, struct dentry *dentry,
+static int unionfs_symlink(struct inode *parent, struct dentry *dentry,
const char *symname)
{
int err = 0;
struct dentry *lower_dentry = NULL;
- struct dentry *whiteout_dentry = NULL;
- struct dentry *lower_dir_dentry = NULL;
- umode_t mode;
- int bindex = 0, bstart;
+ struct dentry *wh_dentry = NULL;
+ struct dentry *lower_parent_dentry = NULL;
char *name = NULL;
+ int valid = 0;
+ umode_t mode;
unionfs_read_lock(dentry->d_sb);
unionfs_lock_dentry(dentry);
@@ -388,147 +388,127 @@ static int unionfs_symlink(struct inode *dir, struct dentry *dentry,
goto out;
}
- /* We start out in the leftmost branch. */
- bstart = dbstart(dentry);
-
- lower_dentry = unionfs_lower_dentry(dentry);
-
/*
- * check if whiteout exists in this branch, i.e. lookup .wh.foo
- * first. If present, delete it
+ * It's only a bug if this dentry was not negative and couldn't be
+ * revalidated (shouldn't happen).
*/
- name = alloc_whname(dentry->d_name.name, dentry->d_name.len);
- if (unlikely(IS_ERR(name))) {
- err = PTR_ERR(name);
- goto out;
- }
+ BUG_ON(!valid && dentry->d_inode);
- whiteout_dentry =
- lookup_one_len(name, lower_dentry->d_parent,
- dentry->d_name.len + UNIONFS_WHLEN);
- if (IS_ERR(whiteout_dentry)) {
- err = PTR_ERR(whiteout_dentry);
+ /*
+ * We shouldn't create things in a read-only branch; this check is a
+ * bit redundant as we don't allow branch 0 to be read-only at the
+ * moment
+ */
+ err = is_robranch_super(dentry->d_sb, 0);
+ if (err) {
+ err = -EROFS;
goto out;
}
- if (!whiteout_dentry->d_inode) {
- dput(whiteout_dentry);
- whiteout_dentry = NULL;
- } else {
+ /*
+ * We _always_ create on branch 0
+ */
+ lower_dentry = unionfs_lower_dentry_idx(dentry, 0);
+ if (lower_dentry) {
/*
- * found a .wh.foo entry, unlink it and then call
- * vfs_symlink().
+ * check if whiteout exists in this branch, i.e. lookup .wh.foo
+ * first.
*/
- lower_dir_dentry = lock_parent(whiteout_dentry);
-
- err = is_robranch_super(dentry->d_sb, bstart);
- if (!err)
- err = vfs_unlink(lower_dir_dentry->d_inode,
- whiteout_dentry);
- dput(whiteout_dentry);
-
- fsstack_copy_attr_times(dir, lower_dir_dentry->d_inode);
- /* propagate number of hard-links */
- dir->i_nlink = unionfs_get_nlinks(dir);
+ name = alloc_whname(dentry->d_name.name, dentry->d_name.len);
+ if (unlikely(IS_ERR(name))) {
+ err = PTR_ERR(name);
+ goto out;
+ }
- unlock_dir(lower_dir_dentry);
+ wh_dentry = lookup_one_len(name, lower_dentry->d_parent,
+ dentry->d_name.len + UNIONFS_WHLEN);
+ if (IS_ERR(wh_dentry)) {
+ err = PTR_ERR(wh_dentry);
+ wh_dentry = NULL;
+ goto out;
+ }
- if (err) {
- /* exit if the error returned was NOT -EROFS */
- if (!IS_COPYUP_ERR(err))
- goto out;
+ if (wh_dentry->d_inode) {
/*
- * should now try to create symlink in the another
- * branch.
+ * .wh.foo has been found, so let's unlink it
*/
- bstart--;
- }
- }
+ struct dentry *lower_dir_dentry;
+
+ lower_dir_dentry = lock_parent(wh_dentry);
+ err = vfs_unlink(lower_dir_dentry->d_inode, wh_dentry);
+ unlock_dir(lower_dir_dentry);
- /*
- * deleted whiteout if it was present, now do a normal vfs_symlink()
- * with possible recursive directory creation
- */
- for (bindex = bstart; bindex >= 0; bindex--) {
- lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
- if (!lower_dentry) {
/*
- * if lower_dentry is NULL, create the entire
- * dentry directory structure in branch 'bindex'.
- * lower_dentry will NOT be null when bindex ==
- * bstart because lookup passed as a negative
- * unionfs dentry pointing to a lone negative
- * underlying dentry
+ * Whiteouts are special files and should be deleted
+ * no matter what (as if they never existed), in
+ * order to allow this create operation to succeed.
+ * This is especially important in sticky
+ * directories: a whiteout may have been created by
+ * one user, but the newly created file may be
+ * created by another user. Therefore, in order to
+ * maintain Unix semantics, if the vfs_unlink above
+ * ailed, then we have to try to directly unlink the
+ * whiteout. Note: in the ODF version of unionfs,
+ * whiteout are handled much more cleanly.
*/
- lower_dentry = create_parents(dir, dentry,
- dentry->d_name.name,
- bindex);
- if (!lower_dentry || IS_ERR(lower_dentry)) {
- if (IS_ERR(lower_dentry))
- err = PTR_ERR(lower_dentry);
- if (!IS_COPYUP_ERR(err))
- printk(KERN_ERR
- "unionfs: create_parents for "
- "symlink failed: bindex=%d "
- "err=%d\n", bindex, err);
- continue;
+ if (err == -EPERM) {
+ struct inode *inode = lower_dir_dentry->d_inode;
+ err = inode->i_op->unlink(inode, wh_dentry);
+ }
+ if (err) {
+ printk(KERN_ERR "unionfs: symlink: could not "
+ "unlink whiteout, err = %d\n", err);
+ goto out;
}
}
+ } else {
+ /*
+ * if lower_dentry is NULL, create the entire
+ * dentry directory structure in branch 0.
+ */
+ lower_dentry = create_parents(parent, dentry,
+ dentry->d_name.name, 0);
+ if (IS_ERR(lower_dentry)) {
+ err = PTR_ERR(lower_dentry);
+ goto out;
+ }
+ }
- lower_dir_dentry = lock_parent(lower_dentry);
+ lower_parent_dentry = lock_parent(lower_dentry);
+ if (IS_ERR(lower_parent_dentry)) {
+ err = PTR_ERR(lower_parent_dentry);
+ goto out;
+ }
- err = is_robranch_super(dentry->d_sb, bindex);
+ mode = S_IALLUGO;
+ err = vfs_symlink(lower_parent_dentry->d_inode, lower_dentry,
+ symname, mode);
+ if (!err) {
+ err = PTR_ERR(unionfs_interpose(dentry, parent->i_sb, 0));
if (!err) {
- mode = S_IALLUGO;
- err = vfs_symlink(lower_dir_dentry->d_inode,
- lower_dentry, symname, mode);
- }
- unlock_dir(lower_dir_dentry);
-
- if (err || !lower_dentry->d_inode) {
- /*
- * break out of for loop if error returned was NOT
- * -EROFS.
- */
- if (!IS_COPYUP_ERR(err))
- break;
- } else {
- /*
- * Only INTERPOSE_LOOKUP can return a value other
- * than 0 on err.
- */
- err = PTR_ERR(unionfs_interpose(dentry,
- dir->i_sb, 0));
- if (!err) {
- fsstack_copy_attr_times(dir,
- lower_dir_dentry->
- d_inode);
- fsstack_copy_inode_size(dir,
- lower_dir_dentry->
- d_inode);
- /*
- * update number of links on parent
- * directory.
- */
- dir->i_nlink = unionfs_get_nlinks(dir);
- }
- break;
+ unionfs_copy_attr_times(parent);
+ fsstack_copy_inode_size(parent,
+ lower_parent_dentry->d_inode);
+ /* update no. of links on parent directory */
+ parent->i_nlink = unionfs_get_nlinks(parent);
}
}
-out:
- if (!dentry->d_inode)
- d_drop(dentry);
+ unlock_dir(lower_parent_dentry);
+out:
+ dput(wh_dentry);
kfree(name);
+
if (!err)
unionfs_postcopyup_setmnt(dentry);
- unionfs_check_inode(dir);
+ unionfs_check_inode(parent);
+ if (!err)
+ unionfs_check_dentry(dentry->d_parent);
unionfs_check_dentry(dentry);
unionfs_unlock_dentry(dentry);
unionfs_read_unlock(dentry->d_sb);
-
return err;
}
--
1.5.2.2
--
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