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Subject[PATCH 09/21] Unionfs: Bulk of branch-management remount code
Date
From: Erez Zadok <ezk@cs.sunysb.edu>

Signed-off-by: Erez Zadok <ezk@cs.sunysb.edu>
Signed-off-by: Josef 'Jeff' Sipek <jsipek@cs.sunysb.edu>
---
fs/unionfs/main.c | 52 +++--
fs/unionfs/super.c | 612 +++++++++++++++++++++++++++++++++++++++++++++++++++-
fs/unionfs/union.h | 6 +
3 files changed, 646 insertions(+), 24 deletions(-)
diff --git a/fs/unionfs/main.c b/fs/unionfs/main.c
index ed264c7..1c93b13 100644
--- a/fs/unionfs/main.c
+++ b/fs/unionfs/main.c
@@ -181,7 +181,7 @@ void unionfs_reinterpose(struct dentry *dentry)
* 2) it exists
* 3) is a directory
*/
-static int check_branch(struct nameidata *nd)
+int check_branch(struct nameidata *nd)
{
if (!strcmp(nd->dentry->d_sb->s_type->name, "unionfs"))
return -EINVAL;
@@ -211,20 +211,29 @@ static int is_branch_overlap(struct dentry *dent1, struct dentry *dent2)
return (dent == dent1);
}

-/* parse branch mode */
-static int parse_branch_mode(char *name)
+/*
+ * Parse branch mode helper function
+ */
+int __parse_branch_mode(const char *name)
{
- int perms;
- int l = strlen(name);
- if (!strcmp(name + l - 3, "=ro")) {
- perms = MAY_READ;
- name[l - 3] = '\0';
- } else if (!strcmp(name + l - 3, "=rw")) {
- perms = MAY_READ | MAY_WRITE;
- name[l - 3] = '\0';
- } else
- perms = MAY_READ | MAY_WRITE;
+ if (!name)
+ return 0;
+ if (!strcmp(name, "ro"))
+ return MAY_READ;
+ if (!strcmp(name, "rw"))
+ return (MAY_READ | MAY_WRITE);
+ return 0;
+}

+/*
+ * Parse "ro" or "rw" options, but default to "rw" of no mode options
+ * was specified.
+ */
+int parse_branch_mode(const char *name)
+{
+ int perms = __parse_branch_mode(name);
+ if (perms == 0)
+ perms = MAY_READ | MAY_WRITE;
return perms;
}

@@ -271,18 +280,22 @@ static int parse_dirs_option(struct super_block *sb, struct unionfs_dentry_info
goto out;
}

- /* now parsing the string b1:b2=rw:b3=ro:b4 */
+ /* now parsing a string such as "b1:b2=rw:b3=ro:b4" */
branches = 0;
while ((name = strsep(&options, ":")) != NULL) {
int perms;
+ char *mode = strchr(name, '=');

- if (!*name)
+ if (!name || !*name)
continue;

branches++;

- /* strip off =rw or =ro if it is specified. */
- perms = parse_branch_mode(name);
+ /* strip off '=' if any */
+ if (mode)
+ *mode++ = '\0';
+
+ perms = parse_branch_mode(mode);
if (!bindex && !(perms & MAY_WRITE)) {
err = -EINVAL;
goto out;
@@ -305,8 +318,11 @@ static int parse_dirs_option(struct super_block *sb, struct unionfs_dentry_info
hidden_root_info->lower_paths[bindex].dentry = nd.dentry;
hidden_root_info->lower_paths[bindex].mnt = nd.mnt;

+ unionfs_write_lock(sb);
set_branchperms(sb, bindex, perms);
set_branch_count(sb, bindex, 0);
+ new_branch_id(sb, bindex);
+ unionfs_write_unlock(sb);

if (hidden_root_info->bstart < 0)
hidden_root_info->bstart = bindex;
@@ -387,7 +403,7 @@ static struct unionfs_dentry_info *unionfs_parse_options(struct super_block *sb,
char *endptr;
int intval;

- if (!*optname)
+ if (!optname || !*optname)
continue;

optarg = strchr(optname, '=');
diff --git a/fs/unionfs/super.c b/fs/unionfs/super.c
index 037c47d..7f0d174 100644
--- a/fs/unionfs/super.c
+++ b/fs/unionfs/super.c
@@ -143,14 +143,614 @@ static int unionfs_statfs(struct dentry *dentry, struct kstatfs *buf)
return err;
}

-/* We don't support a standard text remount. Eventually it would be nice to
- * support a full-on remount, so that you can have all of the directories
- * change at once, but that would require some pretty complicated matching
- * code.
+/* handle mode changing during remount */
+static int do_remount_mode_option(char *optarg, int cur_branches,
+ struct unionfs_data *new_data,
+ struct path *new_lower_paths)
+{
+ int err = -EINVAL;
+ int perms, idx;
+ char *modename = strchr(optarg, '=');
+ struct nameidata nd;
+
+ /* by now, optarg contains the branch name */
+ if (!*optarg) {
+ printk("unionfs: no branch specified for mode change.\n");
+ goto out;
+ }
+ if (!modename) {
+ printk("unionfs: branch \"%s\" requires a mode.\n", optarg);
+ goto out;
+ }
+ *modename++ = '\0';
+ perms = __parse_branch_mode(modename);
+ if (perms == 0) {
+ printk("unionfs: invalid mode \"%s\" for \"%s\".\n",
+ modename, optarg);
+ goto out;
+ }
+
+ /*
+ * Find matching branch index. For now, this assumes that nothing
+ * has been mounted on top of this Unionfs stack. Once we have /odf
+ * and cache-coherency resolved, we'll address the branch-path
+ * uniqueness.
+ */
+ err = path_lookup(optarg, LOOKUP_FOLLOW, &nd);
+ if (err) {
+ printk(KERN_WARNING "unionfs: error accessing "
+ "hidden directory \"%s\" (error %d)\n",
+ optarg, err);
+ goto out;
+ }
+ for (idx=0; idx<cur_branches; idx++)
+ if (nd.mnt == new_lower_paths[idx].mnt &&
+ nd.dentry == new_lower_paths[idx].dentry)
+ break;
+ path_release(&nd); /* no longer needed */
+ if (idx == cur_branches) {
+ err = -ENOENT; /* err may have been reset above */
+ printk(KERN_WARNING "unionfs: branch \"%s\" "
+ "not found\n", optarg);
+ goto out;
+ }
+ /* check/change mode for existing branch */
+ /* we don't warn if perms==branchperms */
+ new_data[idx].branchperms = perms;
+ err = 0;
+out:
+ return err;
+}
+
+/* handle branch deletion during remount */
+static int do_remount_del_option(char *optarg, int cur_branches,
+ struct unionfs_data *new_data,
+ struct path *new_lower_paths)
+{
+ int err = -EINVAL;
+ int idx;
+ struct nameidata nd;
+ /* optarg contains the branch name to delete */
+
+ /*
+ * Find matching branch index. For now, this assumes that nothing
+ * has been mounted on top of this Unionfs stack. Once we have /odf
+ * and cache-coherency resolved, we'll address the branch-path
+ * uniqueness.
+ */
+ err = path_lookup(optarg, LOOKUP_FOLLOW, &nd);
+ if (err) {
+ printk(KERN_WARNING "unionfs: error accessing "
+ "hidden directory \"%s\" (error %d)\n",
+ optarg, err);
+ goto out;
+ }
+ for (idx=0; idx < cur_branches; idx++)
+ if (nd.mnt == new_lower_paths[idx].mnt &&
+ nd.dentry == new_lower_paths[idx].dentry)
+ break;
+ path_release(&nd); /* no longer needed */
+ if (idx == cur_branches) {
+ printk(KERN_WARNING "unionfs: branch \"%s\" "
+ "not found\n", optarg);
+ err = -ENOENT;
+ goto out;
+ }
+ /* check if there are any open files on the branch to be deleted */
+ if (atomic_read(&new_data[idx].open_files) > 0) {
+ err = -EBUSY;
+ goto out;
+ }
+
+ /*
+ * Now we have to delete the branch. First, release any handles it
+ * has. Then, move the remaining array indexes past "idx" in
+ * new_data and new_lower_paths one to the left. Finally, adjust
+ * cur_branches.
+ */
+ pathput(&new_lower_paths[idx]);
+
+ if (idx < cur_branches - 1) {
+ /* if idx==cur_branches-1, we delete last branch: easy */
+ memmove(&new_data[idx], &new_data[idx+1],
+ (cur_branches - 1 - idx) * sizeof(struct unionfs_data));
+ memmove(&new_lower_paths[idx], &new_lower_paths[idx+1],
+ (cur_branches - 1 - idx) * sizeof(struct path));
+ }
+
+ err = 0;
+out:
+ return err;
+}
+
+/* handle branch insertion during remount */
+static int do_remount_add_option(char *optarg, int cur_branches,
+ struct unionfs_data *new_data,
+ struct path *new_lower_paths,
+ int *high_branch_id)
+{
+ int err = -EINVAL;
+ int perms;
+ int idx = 0; /* default: insert at beginning */
+ char *new_branch , *modename = NULL;
+ struct nameidata nd;
+
+ /*
+ * optarg can be of several forms:
+ *
+ * /bar:/foo insert /foo before /bar
+ * /bar:/foo=ro insert /foo in ro mode before /bar
+ * /foo insert /foo in the beginning (prepend)
+ * :/foo insert /foo at the end (append)
+ */
+ if (*optarg == ':') { /* append? */
+ new_branch = optarg + 1; /* skip ':' */
+ idx = cur_branches;
+ goto found_insertion_point;
+ }
+ new_branch = strchr(optarg, ':');
+ if (!new_branch) { /* prepend? */
+ new_branch = optarg;
+ goto found_insertion_point;
+ }
+ *new_branch++ = '\0'; /* holds path+mode of new branch */
+
+ /*
+ * Find matching branch index. For now, this assumes that nothing
+ * has been mounted on top of this Unionfs stack. Once we have /odf
+ * and cache-coherency resolved, we'll address the branch-path
+ * uniqueness.
+ */
+ err = path_lookup(optarg, LOOKUP_FOLLOW, &nd);
+ if (err) {
+ printk(KERN_WARNING "unionfs: error accessing "
+ "hidden directory \"%s\" (error %d)\n",
+ optarg, err);
+ goto out;
+ }
+ for (idx=0; idx < cur_branches; idx++)
+ if (nd.mnt == new_lower_paths[idx].mnt &&
+ nd.dentry == new_lower_paths[idx].dentry)
+ break;
+ path_release(&nd); /* no longer needed */
+ if (idx == cur_branches) {
+ printk(KERN_WARNING "unionfs: branch \"%s\" "
+ "not found\n", optarg);
+ err = -ENOENT;
+ goto out;
+ }
+
+ /*
+ * At this point idx will hold the index where the new branch should
+ * be inserted before.
+ */
+found_insertion_point:
+ /* find the mode for the new branch */
+ if (new_branch)
+ modename = strchr(new_branch, '=');
+ if (modename)
+ *modename++ = '\0';
+ perms = parse_branch_mode(modename);
+
+ if (!new_branch || !*new_branch) {
+ printk(KERN_WARNING "unionfs: null new branch\n");
+ err = -EINVAL;
+ goto out;
+ }
+ err = path_lookup(new_branch, LOOKUP_FOLLOW, &nd);
+ if (err) {
+ printk(KERN_WARNING "unionfs: error accessing "
+ "hidden directory \"%s\" (error %d)\n",
+ new_branch, err);
+ goto out;
+ }
+ /* it's probably safe to check_mode the new branch to insert */
+ if ((err = check_branch(&nd))) {
+ printk(KERN_WARNING "unionfs: hidden directory "
+ "\"%s\" is not a valid branch\n", optarg);
+ path_release(&nd);
+ goto out;
+ }
+
+ /*
+ * Now we have to insert the new branch. But first, move the bits
+ * to make space for the new branch, if needed. Finally, adjust
+ * cur_branches.
+ * We don't release nd here; it's kept until umount/remount.
+ */
+ if (idx < cur_branches) {
+ /* if idx==cur_branches, we append: easy */
+ memmove(&new_data[idx+1], &new_data[idx],
+ (cur_branches - idx) * sizeof(struct unionfs_data));
+ memmove(&new_lower_paths[idx+1], &new_lower_paths[idx],
+ (cur_branches - idx) * sizeof(struct path));
+ }
+ new_lower_paths[idx].dentry = nd.dentry;
+ new_lower_paths[idx].mnt = nd.mnt;
+
+ new_data[idx].sb = nd.dentry->d_sb;
+ atomic_set(&new_data[idx].open_files, 0);
+ new_data[idx].branchperms = perms;
+ new_data[idx].branch_id = ++*high_branch_id; /* assign new branch ID */
+
+ err = 0;
+out:
+ return err;
+}
+
+
+/*
+ * Support branch management options on remount.
+ *
+ * See Documentation/filesystems/unionfs/ for details.
+ *
+ * @flags: numeric mount options
+ * @options: mount options string
+ *
+ * This function can rearrange a mounted union dynamically, adding and
+ * removing branches, including changing branch modes. Clearly this has to
+ * be done safely and atomically. Luckily, the VFS already calls this
+ * function with lock_super(sb) and lock_kernel() held, preventing
+ * concurrent mixing of new mounts, remounts, and unmounts. Moreover,
+ * do_remount_sb(), our caller function, already called shrink_dcache_sb(sb)
+ * to purge dentries/inodes from our superblock, and also called
+ * fsync_super(sb) to purge any dirty pages. So we're good.
+ *
+ * XXX: however, our remount code may also need to invalidate mapped pages
+ * so as to force them to be re-gotten from the (newly reconfigured) lower
+ * branches. This has to wait for proper mmap and cache coherency support
+ * in the VFS.
+ *
*/
-static int unionfs_remount_fs(struct super_block *sb, int *flags, char *data)
+static int unionfs_remount_fs(struct super_block *sb, int *flags,
+ char *options)
{
- return -ENOSYS;
+ int err = 0;
+ int i;
+ char *optionstmp, *tmp_to_free; /* kstrdup'ed of "options" */
+ char *optname;
+ int cur_branches; /* no. of current branches */
+ int new_branches; /* no. of branches actually left in the end */
+ int add_branches; /* est. no. of branches to add */
+ int del_branches; /* est. no. of branches to del */
+ int max_branches; /* max possible no. of branches */
+ struct unionfs_data *new_data = NULL, *tmp_data = NULL;
+ struct path *new_lower_paths = NULL, *tmp_lower_paths = NULL;
+ int new_high_branch_id; /* new high branch ID */
+
+ unionfs_write_lock(sb);
+
+ /*
+ * The VFS will take care of "ro" and "rw" flags, so anything else
+ * is an error. So we need to check if any other flags may have
+ * been passed (none are allowed/supported as of now).
+ */
+ if ((*flags & ~MS_RDONLY) != 0) {
+ printk(KERN_WARNING
+ "unionfs: remount flags 0x%x unsupported\n", *flags);
+ err = -EINVAL;
+ goto out_error;
+ }
+
+ /*
+ * If 'options' is NULL, it's probably because the user just changed
+ * the union to a "ro" or "rw" and the VFS took care of it. So
+ * nothing to do and we're done.
+ */
+ if (options[0] == '\0')
+ goto out_error;
+
+ /*
+ * Find out how many branches we will have in the end, counting
+ * "add" and "del" commands. Copy the "options" string because
+ * strsep modifies the string and we need it later.
+ */
+ optionstmp = tmp_to_free = kstrdup(options, GFP_KERNEL);
+ if (!optionstmp) {
+ err = -ENOMEM;
+ goto out_free;
+ }
+ new_branches = cur_branches = sbmax(sb); /* current no. branches */
+ add_branches = del_branches = 0;
+ new_high_branch_id = sbhbid(sb); /* save current high_branch_id */
+ while ((optname = strsep(&optionstmp, ",")) != NULL) {
+ char *optarg;
+
+ if (!optname || !*optname)
+ continue;
+
+ optarg = strchr(optname, '=');
+ if (optarg)
+ *optarg++ = '\0';
+
+ if (!strcmp("add", optname))
+ add_branches++;
+ else if (!strcmp("del", optname))
+ del_branches++;
+ }
+ kfree(tmp_to_free);
+ /* after all changes, will we have at least one branch left? */
+ if ((new_branches + add_branches - del_branches) < 1) {
+ printk(KERN_WARNING
+ "unionfs: no branches left after remount\n");
+ err = -EINVAL;
+ goto out_free;
+ }
+
+ /*
+ * Since we haven't actually parsed all the add/del options, nor
+ * have we checked them for errors, we don't know for sure how many
+ * branches we will have after all changes have taken place. In
+ * fact, the total number of branches left could be less than what
+ * we have now. So we need to allocate space for a temporary
+ * placeholder that is at least as large as the maximum number of
+ * branches we *could* have, which is the current number plus all
+ * the additions. Once we're done with these temp placeholders, we
+ * may have to re-allocate the final size, copy over from the temp,
+ * and then free the temps (done near the end of this function).
+ */
+ max_branches = cur_branches + add_branches;
+ /* allocate space for new pointers to hidden dentry */
+ tmp_data = kcalloc(max_branches,
+ sizeof(struct unionfs_data), GFP_KERNEL);
+ if (!tmp_data) {
+ err = -ENOMEM;
+ goto out_free;
+ }
+ /* allocate space for new pointers to lower paths */
+ tmp_lower_paths = kcalloc(max_branches,
+ sizeof(struct path), GFP_KERNEL);
+ if (!tmp_lower_paths) {
+ err = -ENOMEM;
+ goto out_free;
+ }
+ /* copy current info into new placeholders, incrementing refcnts */
+ memcpy(tmp_data, UNIONFS_SB(sb)->data,
+ cur_branches * sizeof(struct unionfs_data));
+ memcpy(tmp_lower_paths, UNIONFS_D(sb->s_root)->lower_paths,
+ cur_branches * sizeof(struct path));
+ for (i=0; i<cur_branches; i++)
+ pathget(&tmp_lower_paths[i]); /* drop refs at end of fxn */
+
+ /*******************************************************************
+ * For each branch command, do path_lookup on the requested branch,
+ * and apply the change to a temp branch list. To handle errors, we
+ * already dup'ed the old arrays (above), and increased the refcnts
+ * on various f/s objects. So now we can do all the path_lookups
+ * and branch-management commands on the new arrays. If it fail mid
+ * way, we free the tmp arrays and *put all objects. If we succeed,
+ * then we free old arrays and *put its objects, and then replace
+ * the arrays with the new tmp list (we may have to re-allocate the
+ * memory because the temp lists could have been larger than what we
+ * actually needed).
+ *******************************************************************/
+
+ while ((optname = strsep(&options, ",")) != NULL) {
+ char *optarg;
+
+ if (!optname || !*optname)
+ continue;
+ /*
+ * At this stage optname holds a comma-delimited option, but
+ * without the commas. Next, we need to break the string on
+ * the '=' symbol to separate CMD=ARG, where ARG itself can
+ * be KEY=VAL. For example, in mode=/foo=rw, CMD is "mode",
+ * KEY is "/foo", and VAL is "rw".
+ */
+ optarg = strchr(optname, '=');
+ if (optarg)
+ *optarg++ = '\0';
+ /* incgen remount option (instead of old ioctl) */
+ if (!strcmp("incgen", optname)) {
+ err = 0;
+ goto out_no_change;
+ }
+
+ /*
+ * All of our options take an argument now. (Insert ones
+ * that don't above this check.) So at this stage optname
+ * contains the CMD part and optarg contains the ARG part.
+ */
+ if (!optarg || !*optarg) {
+ printk("unionfs: all remount options require "
+ "an argument (%s).\n", optname);
+ err = -EINVAL;
+ goto out_release;
+ }
+
+ if (!strcmp("add", optname)) {
+ err = do_remount_add_option(optarg, new_branches,
+ tmp_data,
+ tmp_lower_paths,
+ &new_high_branch_id);
+ if (err)
+ goto out_release;
+ new_branches++;
+ if (new_branches > UNIONFS_MAX_BRANCHES) {
+ printk("unionfs: command exceeds %d branches\n",
+ UNIONFS_MAX_BRANCHES);
+ err = -E2BIG;
+ goto out_release;
+ }
+ continue;
+ }
+ if (!strcmp("del", optname)) {
+ err = do_remount_del_option(optarg, new_branches,
+ tmp_data,
+ tmp_lower_paths);
+ if (err)
+ goto out_release;
+ new_branches--;
+ continue;
+ }
+ if (!strcmp("mode", optname)) {
+ err = do_remount_mode_option(optarg, new_branches,
+ tmp_data,
+ tmp_lower_paths);
+ if (err)
+ goto out_release;
+ continue;
+ }
+
+ /*
+ * When you use "mount -o remount,ro", mount(8) will
+ * reportedly pass the original dirs= string from
+ * /proc/mounts. So for now, we have to ignore dirs= and
+ * not consider it an error, unless we want to allow users
+ * to pass dirs= in remount. Note that to allow the VFS to
+ * actually process the ro/rw remount options, we have to
+ * return 0 from this function.
+ */
+ if (!strcmp("dirs", optname)) {
+ printk(KERN_WARNING
+ "unionfs: remount ignoring option \"%s\".\n",
+ optname);
+ continue;
+ }
+
+ err = -EINVAL;
+ printk(KERN_WARNING
+ "unionfs: unrecognized option \"%s\"\n", optname);
+ goto out_release;
+ }
+
+out_no_change:
+
+ /******************************************************************
+ * WE'RE ALMOST DONE: see if we need to allocate a small-sized new
+ * vector, copy the vectors to their correct place, release the
+ * refcnt of the older ones, and return.
+ * Also handle invalidating any pgaes that will have to be re-read.
+ *******************************************************************/
+
+ /*
+ * Allocate space for actual pointers, if needed. By the time we
+ * finish this block of code, new_branches and new_lower_paths will
+ * have the correct size. None of this code below would be needed
+ * if the kernel had a realloc() function, at least one capable of
+ * shrinking/truncating an allocation's size (hint, hint).
+ */
+ if (new_branches < max_branches) {
+
+ /* allocate space for new pointers to hidden dentry */
+ new_data = kcalloc(new_branches,
+ sizeof(struct unionfs_data), GFP_KERNEL);
+ if (!new_data) {
+ err = -ENOMEM;
+ goto out_release;
+ }
+ /* allocate space for new pointers to lower paths */
+ new_lower_paths = kcalloc(new_branches,
+ sizeof(struct path), GFP_KERNEL);
+ if (!new_lower_paths) {
+ err = -ENOMEM;
+ goto out_release;
+ }
+ /*
+ * copy current info into new placeholders, incrementing
+ * refcounts.
+ */
+ memcpy(new_data, tmp_data,
+ new_branches * sizeof(struct unionfs_data));
+ memcpy(new_lower_paths, tmp_lower_paths,
+ new_branches * sizeof(struct path));
+ /*
+ * Since we already hold various refcnts on the objects, we
+ * don't need to redo it here. Just free the older memory
+ * and re-point the pointers.
+ */
+ kfree(tmp_data);
+ kfree(tmp_lower_paths);
+ /* no need to nullify pointers here */
+ } else {
+ /* number of branches didn't change, no need to re-alloc */
+ new_data = tmp_data;
+ new_lower_paths = tmp_lower_paths;
+ }
+
+ /*
+ * OK, just before we actually put the new set of branches in place,
+ * we need to ensure that our own f/s has no dirty objects left.
+ * Luckily, do_remount_sb() already calls shrink_dcache_sb(sb) and
+ * fsync_super(sb), taking care of dentries, inodes, and dirty
+ * pages. So all that's left is for us to invalidate any leftover
+ * (non-dirty) pages to ensure that they will be re-read from the
+ * new lower branches (and to support mmap).
+ */
+
+ /*
+ * No we call drop_pagecache_sb() to invalidate all pages in this
+ * super. This function calls invalidate_inode_pages(mapping),
+ * which calls invalidate_mapping_pages(): the latter, however, will
+ * not invalidate pages which are dirty, locked, under writeback, or
+ * mapped into pagetables. We shouldn't have to worry about dirty
+ * or under-writeback pages, because do_remount_sb() called
+ * fsync_super() which would not have returned until all dirty pages
+ * were flushed.
+ *
+ * But do w have to worry about locked pages? Is there any chance
+ * that in here we'll get locked pages?
+ *
+ * XXX: what about pages mapped into pagetables? Are these pages
+ * which user processes may have mmap(2)'ed? If so, then we need to
+ * invalidate those too, no? Maybe we'll have to write our own
+ * version of invalidate_mapping_pages() which also handled mapped
+ * pages.
+ *
+ * XXX: Alternatively, maybe we should call truncate_inode_pages(),
+ * which use two passes over the pages list, and will truncate all
+ * pages.
+ */
+ drop_pagecache_sb(sb);
+
+ /* copy new vectors into their correct place */
+ tmp_data = UNIONFS_SB(sb)->data;
+ UNIONFS_SB(sb)->data = new_data;
+ new_data = NULL; /* so don't free good pointers below */
+ tmp_lower_paths = UNIONFS_D(sb->s_root)->lower_paths;
+ UNIONFS_D(sb->s_root)->lower_paths = new_lower_paths;
+ new_lower_paths = NULL; /* so don't free good pointers below */
+
+ /* update our unionfs_sb_info and root dentry index of last branch */
+ i = sbmax(sb); /* save no. of branches to release at end */
+ sbend(sb) = new_branches - 1;
+ set_dbend(sb->s_root, new_branches - 1);
+ UNIONFS_D(sb->s_root)->bcount = new_branches;
+ new_branches = i; /* no. of branches to release below */
+
+ /* maxbytes may have changed */
+ sb->s_maxbytes = unionfs_lower_super_idx(sb, 0)->s_maxbytes;
+ /* update high branch ID */
+ sbhbid(sb) = new_high_branch_id;
+
+ /* update our sb->generation for revalidating objects */
+ i = atomic_inc_return(&UNIONFS_SB(sb)->generation);
+ atomic_set(&UNIONFS_D(sb->s_root)->generation, i);
+ atomic_set(&UNIONFS_I(sb->s_root->d_inode)->generation, i);
+ printk("unionfs: new generation number %d\n", i);
+ err = 0; /* reset to success */
+
+ /*
+ * The code above falls through to the next label, and releases the
+ * refcnts of the older ones (stored in tmp_*): if we fell through
+ * here, it means success. However, if we jump directly to this
+ * label from any error above, then an error occurred after we
+ * grabbed various refcnts, and so we have to release the
+ * temporarily constructed structures.
+ */
+out_release:
+ /* no need to cleanup/release anything in tmp_data */
+ if (tmp_lower_paths)
+ for (i=0; i<new_branches; i++)
+ pathput(&tmp_lower_paths[i]);
+out_free:
+ kfree(tmp_lower_paths);
+ kfree(tmp_data);
+ kfree(new_lower_paths);
+ kfree(new_data);
+out_error:
+ unionfs_write_unlock(sb);
+ return err;
}

/*
diff --git a/fs/unionfs/union.h b/fs/unionfs/union.h
index 7bd6306..715a3ad 100644
--- a/fs/unionfs/union.h
+++ b/fs/unionfs/union.h
@@ -60,6 +60,9 @@
/* number of times we try to get a unique temporary file name */
#define GET_TMPNAM_MAX_RETRY 5

+/* maximum number of branches we support, to avoid memory blowup */
+#define UNIONFS_MAX_BRANCHES 128
+
/* Operations vectors defined in specific files. */
extern struct file_operations unionfs_main_fops;
extern struct file_operations unionfs_dir_fops;
@@ -408,6 +411,9 @@ static inline int is_robranch(const struct dentry *dentry)
* EXTERNALS:
*/
extern char *alloc_whname(const char *name, int len);
+extern int check_branch(struct nameidata *nd);
+extern int __parse_branch_mode(const char *name);
+extern int parse_branch_mode(const char *name);

/* These two functions are here because it is kind of daft to copy and paste the
* contents of the two functions to 32+ places in unionfs
--
1.5.0.3.268.g3dda
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