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exportfs: move most of reconnect_path to helper function

Browse source 
Also replace 3 easily-confused three-letter acronyms by more helpful
variable names.

Just cleanup, no change in functionality, with one exception: the
dentry_connected() check in the "out_reconnected" case will now only
check the ancestors of the current dentry instead of checking all the
way from target_dir.  Since we've already verified connectivity up to
this dentry, that should be sufficient.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
J. Bruce Fields 2013-10-17 11:13:00 -04:00 committed by Al Viro
parent e4b70ebeeb
commit bbf7a8a356
1 changed files with 86 additions and 78 deletions
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164
fs/exportfs/expfs.c
View file

@ -125,6 +125,86 @@ static void clear_disconnected(struct dentry *dentry)
dput(dentry);
}
/*
* Reconnect a directory dentry with its parent.
*
* This can return a dentry, or NULL, or an error.
*
* In the first case the returned dentry is the parent of the given
* dentry, and may itself need to be reconnected to its parent.
*
* In the NULL case, a concurrent VFS operation has either renamed or
* removed this directory. The concurrent operation has reconnected our
* dentry, so we no longer need to.
*/
static struct dentry *reconnect_one(struct vfsmount *mnt,
struct dentry *dentry, char *nbuf)
{
struct dentry *parent;
struct dentry *tmp;
int err;
parent = ERR_PTR(-EACCES);
mutex_lock(&dentry->d_inode->i_mutex);
if (mnt->mnt_sb->s_export_op->get_parent)
parent = mnt->mnt_sb->s_export_op->get_parent(dentry);
mutex_unlock(&dentry->d_inode->i_mutex);
if (IS_ERR(parent)) {
dprintk("%s: get_parent of %ld failed, err %d\n",
__func__, dentry->d_inode->i_ino, PTR_ERR(parent));
return parent;
}
dprintk("%s: find name of %lu in %lu\n", __func__,
dentry->d_inode->i_ino, parent->d_inode->i_ino);
err = exportfs_get_name(mnt, parent, nbuf, dentry);
if (err == -ENOENT)
goto out_reconnected;
if (err)
goto out_err;
dprintk("%s: found name: %s\n", __func__, nbuf);
mutex_lock(&parent->d_inode->i_mutex);
tmp = lookup_one_len(nbuf, parent, strlen(nbuf));
mutex_unlock(&parent->d_inode->i_mutex);
if (IS_ERR(tmp)) {
dprintk("%s: lookup failed: %d\n", __func__, PTR_ERR(tmp));
goto out_err;
}
if (tmp != dentry) {
dput(tmp);
goto out_reconnected;
}
dput(tmp);
if (IS_ROOT(dentry)) {
err = -ESTALE;
goto out_err;
}
return parent;
out_err:
dput(parent);
return ERR_PTR(err);
out_reconnected:
dput(parent);
/*
* Someone must have renamed our entry into another parent, in
* which case it has been reconnected by the rename.
*
* Or someone removed it entirely, in which case filehandle
* lookup will succeed but the directory is now IS_DEAD and
* subsequent operations on it will fail.
*
* Alternatively, maybe there was no race at all, and the
* filesystem is just corrupt and gave us a parent that doesn't
* actually contain any entry pointing to this inode. So,
* double check that this worked and return -ESTALE if not:
*/
if (!dentry_connected(dentry))
return ERR_PTR(-ESTALE);
return NULL;
}
/*
* Make sure target_dir is fully connected to the dentry tree.
*
@ -158,76 +238,19 @@ reconnect_path(struct vfsmount *mnt, struct dentry *target_dir, char *nbuf)
dput(pd);
break;
} else {
struct dentry *parent;
/*
* We have hit the top of a disconnected path, try to
* find parent and connect.
*
* Racing with some other process renaming a directory
* isn't much of a problem here. If someone renames
* the directory, it will end up properly connected,
* which is what we want
*
* Getting the parent can't be supported generically,
* the locking is too icky.
*
* Instead we just return EACCES. If server reboots
* or inodes get flushed, you lose
*/
struct dentry *ppd = ERR_PTR(-EACCES);
struct dentry *npd;
mutex_lock(&pd->d_inode->i_mutex);
if (mnt->mnt_sb->s_export_op->get_parent)
ppd = mnt->mnt_sb->s_export_op->get_parent(pd);
mutex_unlock(&pd->d_inode->i_mutex);
if (IS_ERR(ppd)) {
err = PTR_ERR(ppd);
dprintk("%s: get_parent of %ld failed, err %d\n",
__func__, pd->d_inode->i_ino, err);
dput(pd);
break;
}
dprintk("%s: find name of %lu in %lu\n", __func__,
pd->d_inode->i_ino, ppd->d_inode->i_ino);
err = exportfs_get_name(mnt, ppd, nbuf, pd);
if (err) {
dput(ppd);
dput(pd);
if (err == -ENOENT)
/* some race between get_parent and
* get_name?
*/
goto out_reconnected;
break;
}
dprintk("%s: found name: %s\n", __func__, nbuf);
mutex_lock(&ppd->d_inode->i_mutex);
npd = lookup_one_len(nbuf, ppd, strlen(nbuf));
mutex_unlock(&ppd->d_inode->i_mutex);
if (IS_ERR(npd)) {
err = PTR_ERR(npd);
dprintk("%s: lookup failed: %d\n",
__func__, err);
dput(ppd);
dput(pd);
break;
}
/* we didn't really want npd, we really wanted
* a side-effect of the lookup.
* hopefully, npd == pd, though it isn't really
* a problem if it isn't
*/
dput(npd);
dput(ppd);
if (npd != pd)
parent = reconnect_one(mnt, pd, nbuf);
if (!parent)
goto out_reconnected;
if (IS_ROOT(pd)) {
/* something went wrong, we have to give up */
dput(pd);
if (IS_ERR(parent)) {
err = PTR_ERR(parent);
break;
}
dput(parent);
}
dput(pd);
}
@ -241,21 +264,6 @@ reconnect_path(struct vfsmount *mnt, struct dentry *target_dir, char *nbuf)
return 0;
out_reconnected:
/*
* Someone must have renamed our entry into another parent, in
* which case it has been reconnected by the rename.
*
* Or someone removed it entirely, in which case filehandle
* lookup will succeed but the directory is now IS_DEAD and
* subsequent operations on it will fail.
*
* Alternatively, maybe there was no race at all, and the
* filesystem is just corrupt and gave us a parent that doesn't
* actually contain any entry pointing to this inode. So,
* double check that this worked and return -ESTALE if not:
*/
if (!dentry_connected(target_dir))
return -ESTALE;
clear_disconnected(target_dir);
return 0;
}