knfsd: exportfs: split out reconnecting a dentry from find_exported_dentry
There's a clear subfunctionality of reconnecting a given dentry to the main dentry tree in find_exported_dentry, that can be called both for the dentry we're looking for or it's parent directory. This patch splits the subfunctionality out into a separate helper to make the code more readable and document it's intent. As a nice side-optimization we can avoid getting a superfluous dentry reference count in the case we need to reconnect a directory on it's own. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Neil Brown <neilb@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Christoph Hellwig
Linus Torvalds
parent
dd90b50906
commit
019ab801cf
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@ -91,6 +91,129 @@ find_disconnected_root(struct dentry *dentry)
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return dentry;
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}
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/*
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* Make sure target_dir is fully connected to the dentry tree.
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*
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* It may already be, as the flag isn't always updated when connection happens.
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*/
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static int
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reconnect_path(struct super_block *sb, struct dentry *target_dir)
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{
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char nbuf[NAME_MAX+1];
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int noprogress = 0;
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int err = -ESTALE;
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/*
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* It is possible that a confused file system might not let us complete
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* the path to the root. For example, if get_parent returns a directory
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* in which we cannot find a name for the child. While this implies a
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* very sick filesystem we don't want it to cause knfsd to spin. Hence
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* the noprogress counter. If we go through the loop 10 times (2 is
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* probably enough) without getting anywhere, we just give up
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*/
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while (target_dir->d_flags & DCACHE_DISCONNECTED && noprogress++ < 10) {
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struct dentry *pd = find_disconnected_root(target_dir);
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if (!IS_ROOT(pd)) {
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/* must have found a connected parent - great */
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spin_lock(&pd->d_lock);
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pd->d_flags &= ~DCACHE_DISCONNECTED;
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spin_unlock(&pd->d_lock);
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noprogress = 0;
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} else if (pd == sb->s_root) {
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printk(KERN_ERR "export: Eeek filesystem root is not connected, impossible\n");
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spin_lock(&pd->d_lock);
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pd->d_flags &= ~DCACHE_DISCONNECTED;
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spin_unlock(&pd->d_lock);
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noprogress = 0;
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} else {
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/*
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* We have hit the top of a disconnected path, try to
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* find parent and connect.
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*
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* Racing with some other process renaming a directory
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* isn't much of a problem here. If someone renames
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* the directory, it will end up properly connected,
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* which is what we want
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*
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* Getting the parent can't be supported generically,
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* the locking is too icky.
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*
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* Instead we just return EACCES. If server reboots
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* or inodes get flushed, you lose
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*/
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struct dentry *ppd = ERR_PTR(-EACCES);
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struct dentry *npd;
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mutex_lock(&pd->d_inode->i_mutex);
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if (sb->s_export_op->get_parent)
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ppd = sb->s_export_op->get_parent(pd);
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mutex_unlock(&pd->d_inode->i_mutex);
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if (IS_ERR(ppd)) {
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err = PTR_ERR(ppd);
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dprintk("%s: get_parent of %ld failed, err %d\n",
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__FUNCTION__, pd->d_inode->i_ino, err);
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dput(pd);
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break;
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}
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dprintk("%s: find name of %lu in %lu\n", __FUNCTION__,
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pd->d_inode->i_ino, ppd->d_inode->i_ino);
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err = exportfs_get_name(ppd, nbuf, pd);
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if (err) {
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dput(ppd);
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dput(pd);
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if (err == -ENOENT)
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/* some race between get_parent and
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* get_name? just try again
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*/
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continue;
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break;
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}
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dprintk("%s: found name: %s\n", __FUNCTION__, nbuf);
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mutex_lock(&ppd->d_inode->i_mutex);
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npd = lookup_one_len(nbuf, ppd, strlen(nbuf));
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mutex_unlock(&ppd->d_inode->i_mutex);
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if (IS_ERR(npd)) {
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err = PTR_ERR(npd);
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dprintk("%s: lookup failed: %d\n",
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__FUNCTION__, err);
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dput(ppd);
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dput(pd);
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break;
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}
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/* we didn't really want npd, we really wanted
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* a side-effect of the lookup.
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* hopefully, npd == pd, though it isn't really
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* a problem if it isn't
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*/
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if (npd == pd)
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noprogress = 0;
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else
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printk("%s: npd != pd\n", __FUNCTION__);
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dput(npd);
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dput(ppd);
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if (IS_ROOT(pd)) {
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/* something went wrong, we have to give up */
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dput(pd);
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break;
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}
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}
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dput(pd);
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}
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if (target_dir->d_flags & DCACHE_DISCONNECTED) {
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/* something went wrong - oh-well */
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if (!err)
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err = -ESTALE;
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return err;
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}
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return 0;
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}
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/**
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* find_exported_dentry - helper routine to implement export_operations->decode_fh
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* @sb: The &super_block identifying the filesystem
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@ -128,13 +251,8 @@ find_exported_dentry(struct super_block *sb, void *obj, void *parent,
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int (*acceptable)(void *context, struct dentry *de),
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void *context)
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{
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struct dentry *result = NULL;
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struct dentry *target_dir;
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struct dentry *result, *alias;
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int err = -ESTALE;
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struct export_operations *nops = sb->s_export_op;
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struct dentry *alias;
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int noprogress;
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char nbuf[NAME_MAX+1];
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/*
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* Attempt to find the inode.
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@ -151,8 +269,13 @@ find_exported_dentry(struct super_block *sb, void *obj, void *parent,
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goto err_result;
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}
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target_dir = dget(result);
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err = reconnect_path(sb, result);
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if (err)
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goto err_result;
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} else {
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struct dentry *target_dir, *nresult;
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char nbuf[NAME_MAX+1];
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alias = find_acceptable_alias(result, acceptable, context);
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if (alias)
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return alias;
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@ -165,129 +288,21 @@ find_exported_dentry(struct super_block *sb, void *obj, void *parent,
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err = PTR_ERR(target_dir);
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goto err_result;
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}
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}
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/*
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* Now we need to make sure that target_dir is properly connected.
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* It may already be, as the flag isn't always updated when connection
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* happens.
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* So, we walk up parent links until we find a connected directory,
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* or we run out of directories. Then we find the parent, find
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* the name of the child in that parent, and do a lookup.
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* This should connect the child into the parent
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* We then repeat.
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*/
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/* it is possible that a confused file system might not let us complete
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* the path to the root. For example, if get_parent returns a directory
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* in which we cannot find a name for the child. While this implies a
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* very sick filesystem we don't want it to cause knfsd to spin. Hence
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* the noprogress counter. If we go through the loop 10 times (2 is
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* probably enough) without getting anywhere, we just give up
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*/
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noprogress = 0;
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while (target_dir->d_flags & DCACHE_DISCONNECTED && noprogress++ < 10) {
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struct dentry *pd = find_disconnected_root(target_dir);
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if (!IS_ROOT(pd)) {
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/* must have found a connected parent - great */
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spin_lock(&pd->d_lock);
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pd->d_flags &= ~DCACHE_DISCONNECTED;
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spin_unlock(&pd->d_lock);
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noprogress = 0;
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} else if (pd == sb->s_root) {
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printk(KERN_ERR "export: Eeek filesystem root is not connected, impossible\n");
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spin_lock(&pd->d_lock);
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pd->d_flags &= ~DCACHE_DISCONNECTED;
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spin_unlock(&pd->d_lock);
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noprogress = 0;
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} else {
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/*
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* We have hit the top of a disconnected path, try to
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* find parent and connect.
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*
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* Racing with some other process renaming a directory
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* isn't much of a problem here. If someone renames
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* the directory, it will end up properly connected,
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* which is what we want
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*
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* Getting the parent can't be supported generically,
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* the locking is too icky.
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*
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* Instead we just return EACCES. If server reboots
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* or inodes get flushed, you lose
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*/
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struct dentry *ppd = ERR_PTR(-EACCES);
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struct dentry *npd;
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mutex_lock(&pd->d_inode->i_mutex);
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if (nops->get_parent)
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ppd = nops->get_parent(pd);
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mutex_unlock(&pd->d_inode->i_mutex);
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if (IS_ERR(ppd)) {
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err = PTR_ERR(ppd);
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dprintk("find_exported_dentry: get_parent of %ld failed, err %d\n",
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pd->d_inode->i_ino, err);
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dput(pd);
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break;
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}
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dprintk("find_exported_dentry: find name of %lu in %lu\n", pd->d_inode->i_ino, ppd->d_inode->i_ino);
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err = exportfs_get_name(ppd, nbuf, pd);
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if (err) {
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dput(ppd);
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dput(pd);
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if (err == -ENOENT)
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/* some race between get_parent and
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* get_name? just try again
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*/
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continue;
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break;
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}
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dprintk("find_exported_dentry: found name: %s\n", nbuf);
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mutex_lock(&ppd->d_inode->i_mutex);
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npd = lookup_one_len(nbuf, ppd, strlen(nbuf));
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mutex_unlock(&ppd->d_inode->i_mutex);
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if (IS_ERR(npd)) {
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err = PTR_ERR(npd);
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dprintk("find_exported_dentry: lookup failed: %d\n", err);
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dput(ppd);
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dput(pd);
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break;
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}
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/* we didn't really want npd, we really wanted
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* a side-effect of the lookup.
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* hopefully, npd == pd, though it isn't really
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* a problem if it isn't
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*/
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if (npd == pd)
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noprogress = 0;
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else
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printk("find_exported_dentry: npd != pd\n");
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dput(npd);
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dput(ppd);
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if (IS_ROOT(pd)) {
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/* something went wrong, we have to give up */
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dput(pd);
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break;
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}
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err = reconnect_path(sb, target_dir);
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if (err) {
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dput(target_dir);
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goto err_result;
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}
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dput(pd);
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}
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if (target_dir->d_flags & DCACHE_DISCONNECTED) {
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/* something went wrong - oh-well */
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if (!err)
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err = -ESTALE;
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goto err_target;
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}
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/* if we weren't after a directory, have one more step to go */
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if (result != target_dir) {
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struct dentry *nresult;
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/*
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* As we weren't after a directory, have one more step to go.
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*/
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err = exportfs_get_name(target_dir, nbuf, result);
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if (!err) {
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mutex_lock(&target_dir->d_inode->i_mutex);
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nresult = lookup_one_len(nbuf, target_dir, strlen(nbuf));
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nresult = lookup_one_len(nbuf, target_dir,
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strlen(nbuf));
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mutex_unlock(&target_dir->d_inode->i_mutex);
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if (!IS_ERR(nresult)) {
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if (nresult->d_inode) {
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@ -297,8 +312,8 @@ find_exported_dentry(struct super_block *sb, void *obj, void *parent,
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dput(nresult);
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}
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}
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dput(target_dir);
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}
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dput(target_dir);
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alias = find_acceptable_alias(result, acceptable, context);
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if (alias)
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@ -308,13 +323,11 @@ find_exported_dentry(struct super_block *sb, void *obj, void *parent,
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dput(result);
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/* It might be justifiable to return ESTALE here,
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* but the filehandle at-least looks reasonable good
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* and it just be a permission problem, so returning
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* and it may just be a permission problem, so returning
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* -EACCESS is safer
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*/
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return ERR_PTR(-EACCES);
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err_target:
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dput(target_dir);
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err_result:
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dput(result);
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return ERR_PTR(err);
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