Date: Thu, 31 Aug 2006 21:50:16 -0400
From: Josef Sipek <jsipek@cs.sunysb.edu>
To: linux-kernel@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org, hch@infradead.org, akpm@osdl.org,
       viro@ftp.linux.org.uk
Subject: [PATCH 11/22][RFC] Unionfs: Lookup helper functions
Message-ID: <20060901015016.GL5788@fsl.cs.sunysb.edu>
References: <20060901013512.GA5788@fsl.cs.sunysb.edu>
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From: Josef "Jeff" Sipek <jsipek@cs.sunysb.edu>

This patch provides helper functions for the lookup operations in Unionfs.

Signed-off-by: Josef "Jeff" Sipek <jsipek@cs.sunysb.edu>
Signed-off-by: David Quigley <dquigley@fsl.cs.sunysb.edu>
Signed-off-by: Erez Zadok <ezk@cs.sunysb.edu>

---

 fs/unionfs/lookup.c |  477 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 477 insertions(+)

diff -Nur -x linux-2.6-git/Documentation/dontdiff linux-2.6-git/fs/unionfs/lookup.c linux-2.6-git-unionfs/fs/unionfs/lookup.c
--- linux-2.6-git/fs/unionfs/lookup.c	1969-12-31 19:00:00.000000000 -0500
+++ linux-2.6-git-unionfs/fs/unionfs/lookup.c	2006-08-31 19:04:00.000000000 -0400
@@ -0,0 +1,477 @@
+/*
+ * Copyright (c) 2003-2006 Erez Zadok
+ * Copyright (c) 2003-2006 Charles P. Wright
+ * Copyright (c) 2005-2006 Josef 'Jeff' Sipek
+ * Copyright (c) 2005-2006 Junjiro Okajima
+ * Copyright (c) 2005      Arun M. Krishnakumar
+ * Copyright (c) 2004-2006 David P. Quigley
+ * Copyright (c) 2003-2004 Mohammad Nayyer Zubair
+ * Copyright (c) 2003      Puja Gupta
+ * Copyright (c) 2003      Harikesavan Krishnan
+ * Copyright (c) 2003-2006 Stony Brook University
+ * Copyright (c) 2003-2006 The Research Foundation of State University of New York
+ *
+ * For specific licensing information, see the COPYING file distributed with
+ * this package.
+ *
+ * This Copyright notice must be kept intact and distributed with all sources.
+ */
+
+#include "union.h"
+
+static int is_opaque_dir(struct dentry *dentry, int bindex);
+static int is_validname(const char *name);
+
+struct dentry *unionfs_lookup_backend(struct dentry *dentry, int lookupmode)
+{
+	int err = 0;
+	struct dentry *hidden_dentry = NULL;
+	struct dentry *wh_hidden_dentry = NULL;
+	struct dentry *hidden_dir_dentry = NULL;
+	struct dentry *parent_dentry = NULL;
+	int bindex, bstart, bend, bopaque;
+	int dentry_count = 0;	/* Number of positive dentries. */
+	int first_dentry_offset = -1;
+	struct dentry *first_hidden_dentry = NULL;
+	int locked_parent = 0;
+	int locked_child = 0;
+
+	int opaque;
+	char *whname = NULL;
+	const char *name;
+	int namelen;
+
+	/* We should already have a lock on this dentry in the case of a
+	 * partial lookup, or a revalidation. Otherwise it is returned from
+	 * new_dentry_private_data already locked.  */
+	if (lookupmode == INTERPOSE_PARTIAL || lookupmode == INTERPOSE_REVAL
+	    || lookupmode == INTERPOSE_REVAL_NEG) {
+		verify_locked(dentry);
+	} else {
+		BUG_ON(dtopd_nocheck(dentry) != NULL);
+		locked_child = 1;
+	}
+	if (lookupmode != INTERPOSE_PARTIAL)
+		if ((err = new_dentry_private_data(dentry)))
+			goto out;
+	/* must initialize dentry operations */
+	dentry->d_op = &unionfs_dops;
+
+	parent_dentry = dget_parent(dentry);
+	/* We never partial lookup the root directory. */
+	if (parent_dentry != dentry) {
+		lock_dentry(parent_dentry);
+		locked_parent = 1;
+	} else {
+		dput(parent_dentry);
+		parent_dentry = NULL;
+		goto out;
+	}
+
+	name = dentry->d_name.name;
+	namelen = dentry->d_name.len;
+
+	/* No dentries should get created for possible whiteout names. */
+	if (!is_validname(name)) {
+		err = -EPERM;
+		goto out_free;
+	}
+
+	/* Now start the actual lookup procedure. */
+	bstart = dbstart(parent_dentry);
+	bend = dbend(parent_dentry);
+	bopaque = dbopaque(parent_dentry);
+	BUG_ON(bstart < 0);
+
+	/* It would be ideal if we could convert partial lookups to only have
+	 * to do this work when they really need to.  It could probably improve
+	 * performance quite a bit, and maybe simplify the rest of the code. */
+	if (lookupmode == INTERPOSE_PARTIAL) {
+		bstart++;
+		if ((bopaque != -1) && (bopaque < bend))
+			bend = bopaque;
+	}
+
+	for (bindex = bstart; bindex <= bend; bindex++) {
+		hidden_dentry = dtohd_index(dentry, bindex);
+		if (lookupmode == INTERPOSE_PARTIAL && hidden_dentry)
+			continue;
+		BUG_ON(hidden_dentry != NULL);
+
+		hidden_dir_dentry = dtohd_index(parent_dentry, bindex);
+
+		/* if the parent hidden dentry does not exist skip this */
+		if (!(hidden_dir_dentry && hidden_dir_dentry->d_inode))
+			continue;
+
+		/* also skip it if the parent isn't a directory. */
+		if (!S_ISDIR(hidden_dir_dentry->d_inode->i_mode))
+			continue;
+
+		/* Reuse the whiteout name because its value doesn't change. */
+		if (!whname) {
+			whname = alloc_whname(name, namelen);
+			if (IS_ERR(whname)) {
+				err = PTR_ERR(whname);
+				goto out_free;
+			}
+		}
+
+		/* check if whiteout exists in this branch: lookup .wh.foo */
+		wh_hidden_dentry = lookup_one_len(whname, hidden_dir_dentry,
+						  namelen + UNIONFS_WHLEN);
+		if (IS_ERR(wh_hidden_dentry)) {
+			dput(first_hidden_dentry);
+			err = PTR_ERR(wh_hidden_dentry);
+			goto out_free;
+		}
+
+		if (wh_hidden_dentry->d_inode) {
+			/* We found a whiteout so lets give up. */
+			if (S_ISREG(wh_hidden_dentry->d_inode->i_mode)) {
+				set_dbend(dentry, bindex);
+				set_dbopaque(dentry, bindex);
+				dput(wh_hidden_dentry);
+				break;
+			}
+			err = -EIO;
+			printk(KERN_NOTICE "EIO: Invalid whiteout entry type"
+			       " %d.\n", wh_hidden_dentry->d_inode->i_mode);
+			dput(wh_hidden_dentry);
+			dput(first_hidden_dentry);
+			goto out_free;
+		}
+
+		dput(wh_hidden_dentry);
+		wh_hidden_dentry = NULL;
+
+		/* Now do regular lookup; lookup foo */
+		hidden_dentry = lookup_one_len(name, hidden_dir_dentry,
+					       namelen);
+		if (IS_ERR(hidden_dentry)) {
+			dput(first_hidden_dentry);
+			err = PTR_ERR(hidden_dentry);
+			goto out_free;
+		}
+
+		/* Store the first negative dentry specially, because if they
+		 * are all negative we need this for future creates. */
+		if (!hidden_dentry->d_inode) {
+			if (!first_hidden_dentry && (dbstart(dentry) == -1)) {
+				first_hidden_dentry = hidden_dentry;
+				first_dentry_offset = bindex;
+			} else {
+				dput(hidden_dentry);
+			}
+			continue;
+		}
+
+		/* number of positive dentries */
+		dentry_count++;
+
+		/* store underlying dentry */
+		if (dbstart(dentry) == -1)
+			set_dbstart(dentry, bindex);
+		set_dtohd_index(dentry, bindex, hidden_dentry);
+		set_dbend(dentry, bindex);
+
+		/* update parent directory's atime with the bindex */
+		fist_copy_attr_atime(parent_dentry->d_inode,
+				     hidden_dir_dentry->d_inode);
+
+		/* We terminate file lookups here. */
+		if (!S_ISDIR(hidden_dentry->d_inode->i_mode)) {
+			if (lookupmode == INTERPOSE_PARTIAL)
+				continue;
+			if (dentry_count == 1)
+				goto out_positive;
+			/* This can only happen with mixed D-*-F-* */
+			BUG_ON(!S_ISDIR(dtohd(dentry)->d_inode->i_mode));
+			continue;
+		}
+
+		opaque = is_opaque_dir(dentry, bindex);
+		if (opaque < 0) {
+			dput(first_hidden_dentry);
+			err = opaque;
+			goto out_free;
+		}
+		if (opaque) {
+			set_dbend(dentry, bindex);
+			set_dbopaque(dentry, bindex);
+			break;
+		}
+	}
+
+	if (dentry_count)
+		goto out_positive;
+	else
+		goto out_negative;
+
+out_negative:
+	if (lookupmode == INTERPOSE_PARTIAL)
+		goto out;
+
+	/* If we've only got negative dentries, then use the leftmost one. */
+	if (lookupmode == INTERPOSE_REVAL) {
+		if (dentry->d_inode) {
+			itopd(dentry->d_inode)->uii_stale = 1;
+		}
+		goto out;
+	}
+	/* This should only happen if we found a whiteout. */
+	if (first_dentry_offset == -1) {
+		first_hidden_dentry = lookup_one_len(name, hidden_dir_dentry,
+						     namelen);
+		first_dentry_offset = bindex;
+		if (IS_ERR(first_hidden_dentry)) {
+			err = PTR_ERR(first_hidden_dentry);
+			goto out;
+		}
+	}
+	set_dtohd_index(dentry, first_dentry_offset, first_hidden_dentry);
+	set_dbstart(dentry, first_dentry_offset);
+	set_dbend(dentry, first_dentry_offset);
+
+	if (lookupmode == INTERPOSE_REVAL_NEG)
+		BUG_ON(dentry->d_inode != NULL);
+	else
+		d_add(dentry, NULL);
+	goto out;
+
+/* This part of the code is for positive dentries. */
+out_positive:
+	BUG_ON(dentry_count <= 0);
+
+	/* If we're holding onto the first negative dentry throw it out. */
+	dput(first_hidden_dentry);
+
+	/* Partial lookups need to reinterpose, or throw away older negs. */
+	if (lookupmode == INTERPOSE_PARTIAL) {
+		if (dentry->d_inode) {
+			unionfs_reinterpose(dentry);
+			goto out;
+		}
+
+		/* This somehow turned positive, so it is as if we had a
+		 * negative revalidation.  */
+		lookupmode = INTERPOSE_REVAL_NEG;
+
+		update_bstart(dentry);
+		bstart = dbstart(dentry);
+		bend = dbend(dentry);
+	}
+
+	err = unionfs_interpose(dentry, dentry->d_sb, lookupmode);
+	if (err)
+		goto out_drop;
+
+	goto out;
+
+out_drop:
+	d_drop(dentry);
+
+out_free:
+	/* should dput all the underlying dentries on error condition */
+	bstart = dbstart(dentry);
+	if (bstart >= 0) {
+		bend = dbend(dentry);
+		for (bindex = bstart; bindex <= bend; bindex++)
+			dput(dtohd_index(dentry, bindex));
+	}
+	kfree(dtohd_ptr(dentry));
+	dtohd_ptr(dentry) = NULL;
+	set_dbstart(dentry, -1);
+	set_dbend(dentry, -1);
+
+out:
+	if (!err && dtopd(dentry)) {
+		BUG_ON(dbend(dentry) > dtopd(dentry)->udi_bcount);
+		BUG_ON(dbend(dentry) > sbmax(dentry->d_sb));
+		BUG_ON(dbstart(dentry) < 0);
+	}
+	kfree(whname);
+	if (locked_parent)
+		unlock_dentry(parent_dentry);
+	dput(parent_dentry);
+	if (locked_child)
+		unlock_dentry(dentry);
+	return ERR_PTR(err);
+}
+
+/* This is a utility function that fills in a unionfs dentry.*/
+int unionfs_partial_lookup(struct dentry *dentry)
+{
+	struct dentry *tmp;
+
+	tmp = unionfs_lookup_backend(dentry, INTERPOSE_PARTIAL);
+	if (!tmp)
+		return 0;
+	if (IS_ERR(tmp))
+		return PTR_ERR(tmp);
+	/* need to change the interface */
+	BUG_ON(tmp != dentry);
+	return -ENOSYS;
+}
+
+/* The rest of these are utility functions for lookup. */
+static int is_opaque_dir(struct dentry *dentry, int bindex)
+{
+	int err = 0;
+	struct dentry *hidden_dentry;
+	struct dentry *wh_hidden_dentry;
+	struct inode *hidden_inode;
+	struct sioq_args args;
+
+	hidden_dentry = dtohd_index(dentry, bindex);
+	hidden_inode = hidden_dentry->d_inode;
+
+	BUG_ON(!S_ISDIR(hidden_inode->i_mode));
+
+	mutex_lock(&hidden_inode->i_mutex);
+
+	if (!permission(hidden_inode, MAY_EXEC, NULL))
+		wh_hidden_dentry = lookup_one_len(UNIONFS_DIR_OPAQUE, hidden_dentry,
+					sizeof(UNIONFS_DIR_OPAQUE) - 1);
+	else {
+		args.u.isopaque.dentry = hidden_dentry;
+		run_sioq(__is_opaque_dir, &args);
+		wh_hidden_dentry = args.ret;
+	}
+
+	mutex_unlock(&hidden_inode->i_mutex);
+
+	if (IS_ERR(wh_hidden_dentry)) {
+		err = PTR_ERR(wh_hidden_dentry);
+		goto out;
+	}
+
+	/* This is an opaque dir iff wh_hidden_dentry is positive */
+	err = !!wh_hidden_dentry->d_inode;
+
+	dput(wh_hidden_dentry);
+out:
+	return err;
+}
+
+static int is_validname(const char *name)
+{
+	if (!strncmp(name, UNIONFS_WHPFX, UNIONFS_WHLEN))
+		return 0;
+	if (!strncmp(name, UNIONFS_DIR_OPAQUE_NAME,
+		     sizeof(UNIONFS_DIR_OPAQUE_NAME) - 1))
+		return 0;
+	return 1;
+}
+
+/* The dentry cache is just so we have properly sized dentries. */
+static kmem_cache_t *unionfs_dentry_cachep;
+int init_dentry_cache(void)
+{
+	unionfs_dentry_cachep =
+	    kmem_cache_create("unionfs_dentry",
+			      sizeof(struct unionfs_dentry_info), 0,
+			      SLAB_RECLAIM_ACCOUNT, NULL, NULL);
+
+	if (!unionfs_dentry_cachep)
+		return -ENOMEM;
+	return 0;
+}
+
+void destroy_dentry_cache(void)
+{
+	if (!unionfs_dentry_cachep)
+		return;
+	if (kmem_cache_destroy(unionfs_dentry_cachep))
+		printk(KERN_ERR
+		       "unionfs_dentry_cache: not all structures were freed\n");
+	return;
+}
+
+void free_dentry_private_data(struct unionfs_dentry_info *udi)
+{
+	if (!udi)
+		return;
+	kmem_cache_free(unionfs_dentry_cachep, udi);
+}
+
+int new_dentry_private_data(struct dentry *dentry)
+{
+	int newsize;
+	int oldsize = 0;
+
+	spin_lock(&dentry->d_lock);
+	if (!dtopd_nocheck(dentry)) {
+		dtopd_lhs(dentry) = (struct unionfs_dentry_info *)
+		    kmem_cache_alloc(unionfs_dentry_cachep, SLAB_ATOMIC);
+		if (!dtopd_nocheck(dentry))
+			goto out;
+		init_MUTEX_LOCKED(&dtopd_nocheck(dentry)->udi_sem);
+
+		dtohd_ptr(dentry) = NULL;
+	} else {
+		oldsize = sizeof(struct dentry *) * dtopd(dentry)->udi_bcount;
+	}
+
+	dtopd_nocheck(dentry)->udi_bstart = -1;
+	dtopd_nocheck(dentry)->udi_bend = -1;
+	dtopd_nocheck(dentry)->udi_bopaque = -1;
+	dtopd_nocheck(dentry)->udi_bcount = sbmax(dentry->d_sb);
+	atomic_set(&dtopd_nocheck(dentry)->udi_generation,
+		   atomic_read(&stopd(dentry->d_sb)->usi_generation));
+	newsize = sizeof(struct dentry *) * sbmax(dentry->d_sb);
+
+	/* Don't reallocate when we already have enough space. */
+	/* It would be ideal if we could actually use the slab macros to
+	 * determine what our object sizes is, but those are not exported.
+	 */
+	if (oldsize) {
+		int minsize = malloc_sizes[0].cs_size;
+
+		if (!newsize || ((oldsize < newsize) && (newsize > minsize))) {
+			kfree(dtohd_ptr(dentry));
+			dtohd_ptr(dentry) = NULL;
+		}
+	}
+
+	if (!dtohd_ptr(dentry) && newsize) {
+		dtohd_ptr(dentry) = kmalloc(newsize, GFP_ATOMIC);
+		if (!dtohd_ptr(dentry))
+			goto out;
+	}
+
+	if (oldsize > newsize)
+		memset(dtohd_ptr(dentry), 0, oldsize);
+	else
+		memset(dtohd_ptr(dentry), 0, newsize);
+
+	spin_unlock(&dentry->d_lock);
+	return 0;
+
+out:
+	free_dentry_private_data(dtopd_nocheck(dentry));
+	dtopd_lhs(dentry) = NULL;
+	spin_unlock(&dentry->d_lock);
+	return -ENOMEM;
+}
+
+void update_bstart(struct dentry *dentry)
+{
+	int bindex;
+	int bstart = dbstart(dentry);
+	int bend = dbend(dentry);
+	struct dentry *hidden_dentry;
+
+	for (bindex = bstart; bindex <= bend; bindex++) {
+		hidden_dentry = dtohd_index(dentry, bindex);
+		if (!hidden_dentry)
+			continue;
+		if (hidden_dentry->d_inode) {
+			set_dbstart(dentry, bindex);
+			break;
+		}
+		dput(hidden_dentry);
+		set_dtohd_index(dentry, bindex, NULL);
+	}
+}
+
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