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Subject[PATCH 20/29] Unionfs: super_block operations
Date
Includes read_inode, delete_inode, put_super, statfs, remount_fs (which
supports branch-management ops), clear_inode, alloc_inode, destroy_inode,
write_inode, umount_begin, and show_options.

Signed-off-by: Erez Zadok <ezk@cs.sunysb.edu>
---
fs/unionfs/super.c | 1025 ++++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 1025 insertions(+), 0 deletions(-)
create mode 100644 fs/unionfs/super.c
diff --git a/fs/unionfs/super.c b/fs/unionfs/super.c
new file mode 100644
index 0000000..986c980
--- /dev/null
+++ b/fs/unionfs/super.c
@@ -0,0 +1,1025 @@
+/*
+ * Copyright (c) 2003-2007 Erez Zadok
+ * Copyright (c) 2003-2006 Charles P. Wright
+ * Copyright (c) 2005-2007 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) 2003-2007 Stony Brook University
+ * Copyright (c) 2003-2007 The Research Foundation of SUNY
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include "union.h"
+
+/*
+ * The inode cache is used with alloc_inode for both our inode info and the
+ * vfs inode.
+ */
+static struct kmem_cache *unionfs_inode_cachep;
+
+static void unionfs_read_inode(struct inode *inode)
+{
+ int size;
+ struct unionfs_inode_info *info = UNIONFS_I(inode);
+
+ memset(info, 0, offsetof(struct unionfs_inode_info, vfs_inode));
+ info->bstart = -1;
+ info->bend = -1;
+ atomic_set(&info->generation,
+ atomic_read(&UNIONFS_SB(inode->i_sb)->generation));
+ spin_lock_init(&info->rdlock);
+ info->rdcount = 1;
+ info->hashsize = -1;
+ INIT_LIST_HEAD(&info->readdircache);
+
+ size = sbmax(inode->i_sb) * sizeof(struct inode *);
+ info->lower_inodes = kzalloc(size, GFP_KERNEL);
+ if (unlikely(!info->lower_inodes)) {
+ printk(KERN_CRIT "unionfs: no kernel memory when allocating "
+ "lower-pointer array!\n");
+ BUG();
+ }
+
+ inode->i_version++;
+ inode->i_op = &unionfs_main_iops;
+ inode->i_fop = &unionfs_main_fops;
+
+ inode->i_mapping->a_ops = &unionfs_aops;
+
+ /*
+ * reset times so unionfs_copy_attr_all can keep out time invariants
+ * right (upper inode time being the max of all lower ones).
+ */
+ inode->i_atime.tv_sec = inode->i_atime.tv_nsec = 0;
+ inode->i_mtime.tv_sec = inode->i_mtime.tv_nsec = 0;
+ inode->i_ctime.tv_sec = inode->i_ctime.tv_nsec = 0;
+
+}
+
+/*
+ * we now define delete_inode, because there are two VFS paths that may
+ * destroy an inode: one of them calls clear inode before doing everything
+ * else that's needed, and the other is fine. This way we truncate the inode
+ * size (and its pages) and then clear our own inode, which will do an iput
+ * on our and the lower inode.
+ *
+ * No need to lock sb info's rwsem.
+ */
+static void unionfs_delete_inode(struct inode *inode)
+{
+#if BITS_PER_LONG == 32 && defined(CONFIG_SMP)
+ spin_lock(&inode->i_lock);
+#endif
+ i_size_write(inode, 0); /* every f/s seems to do that */
+#if BITS_PER_LONG == 32 && defined(CONFIG_SMP)
+ spin_unlock(&inode->i_lock);
+#endif
+
+ if (inode->i_data.nrpages)
+ truncate_inode_pages(&inode->i_data, 0);
+
+ clear_inode(inode);
+}
+
+/*
+ * final actions when unmounting a file system
+ *
+ * No need to lock rwsem.
+ */
+static void unionfs_put_super(struct super_block *sb)
+{
+ int bindex, bstart, bend;
+ struct unionfs_sb_info *spd;
+ int leaks = 0;
+
+ spd = UNIONFS_SB(sb);
+ if (!spd)
+ return;
+
+ bstart = sbstart(sb);
+ bend = sbend(sb);
+
+ /* Make sure we have no leaks of branchget/branchput. */
+ for (bindex = bstart; bindex <= bend; bindex++)
+ if (unlikely(branch_count(sb, bindex) != 0)) {
+ printk(KERN_CRIT
+ "unionfs: branch %d has %d references left!\n",
+ bindex, branch_count(sb, bindex));
+ leaks = 1;
+ }
+ BUG_ON(leaks != 0);
+
+ kfree(spd->data);
+ kfree(spd);
+ sb->s_fs_info = NULL;
+}
+
+/*
+ * Since people use this to answer the "How big of a file can I write?"
+ * question, we report the size of the highest priority branch as the size of
+ * the union.
+ */
+static int unionfs_statfs(struct dentry *dentry, struct kstatfs *buf)
+{
+ int err = 0;
+ struct super_block *sb;
+ struct dentry *lower_dentry;
+
+ sb = dentry->d_sb;
+
+ unionfs_read_lock(sb, UNIONFS_SMUTEX_CHILD);
+ unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);
+
+ if (unlikely(!__unionfs_d_revalidate_chain(dentry, NULL, false))) {
+ err = -ESTALE;
+ goto out;
+ }
+ unionfs_check_dentry(dentry);
+
+ lower_dentry = unionfs_lower_dentry(sb->s_root);
+ err = vfs_statfs(lower_dentry, buf);
+
+ /* set return buf to our f/s to avoid confusing user-level utils */
+ buf->f_type = UNIONFS_SUPER_MAGIC;
+ /*
+ * Our maximum file name can is shorter by a few bytes because every
+ * file name could potentially be whited-out.
+ *
+ * XXX: this restriction goes away with ODF.
+ */
+ buf->f_namelen -= UNIONFS_WHLEN;
+
+ /*
+ * reset two fields to avoid confusing user-land.
+ * XXX: is this still necessary?
+ */
+ memset(&buf->f_fsid, 0, sizeof(__kernel_fsid_t));
+ memset(&buf->f_spare, 0, sizeof(buf->f_spare));
+
+out:
+ unionfs_check_dentry(dentry);
+ unionfs_unlock_dentry(dentry);
+ unionfs_read_unlock(sb);
+ return err;
+}
+
+/* handle mode changing during remount */
+static noinline 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(KERN_ERR
+ "unionfs: no branch specified for mode change\n");
+ goto out;
+ }
+ if (!modename) {
+ printk(KERN_ERR "unionfs: branch \"%s\" requires a mode\n",
+ optarg);
+ goto out;
+ }
+ *modename++ = '\0';
+ err = parse_branch_mode(modename, &perms);
+ if (err) {
+ printk(KERN_ERR "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_ERR "unionfs: error accessing "
+ "lower 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_ERR "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 noinline 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_ERR "unionfs: error accessing "
+ "lower 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_ERR "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 noinline 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_ERR "unionfs: error accessing "
+ "lower 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_ERR "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';
+ if (!new_branch || !*new_branch) {
+ printk(KERN_ERR "unionfs: null new branch\n");
+ err = -EINVAL;
+ goto out;
+ }
+ err = parse_branch_mode(modename, &perms);
+ if (err) {
+ printk(KERN_ERR "unionfs: invalid mode \"%s\" for "
+ "branch \"%s\"\n", modename, new_branch);
+ goto out;
+ }
+ err = path_lookup(new_branch, LOOKUP_FOLLOW, &nd);
+ if (err) {
+ printk(KERN_ERR "unionfs: error accessing "
+ "lower directory \"%s\" (error %d)\n",
+ new_branch, err);
+ goto out;
+ }
+ /*
+ * It's probably safe to check_mode the new branch to insert. Note:
+ * we don't allow inserting branches which are unionfs's by
+ * themselves (check_branch returns EINVAL in that case). This is
+ * because this code base doesn't support stacking unionfs: the ODF
+ * code base supports that correctly.
+ */
+ err = check_branch(&nd);
+ if (err) {
+ printk(KERN_ERR "unionfs: lower 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 *options)
+{
+ int err = 0;
+ int i;
+ char *optionstmp, *tmp_to_free; /* kstrdup'ed of "options" */
+ char *optname;
+ int cur_branches = 0; /* no. of current branches */
+ int new_branches = 0; /* 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;
+ struct inode **new_lower_inodes = NULL;
+ int new_high_branch_id; /* new high branch ID */
+ int size; /* memory allocation size, temp var */
+ int old_ibstart, old_ibend;
+
+ unionfs_write_lock(sb);
+
+ /*
+ * The VFS will take care of "ro" and "rw" flags, and we can safely
+ * ignore MS_SILENT, but anything else left over 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 | MS_SILENT)) != 0) {
+ printk(KERN_ERR
+ "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 || 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.
+ */
+ tmp_to_free = kstrdup(options, GFP_KERNEL);
+ optionstmp = tmp_to_free;
+ if (unlikely(!optionstmp)) {
+ err = -ENOMEM;
+ goto out_free;
+ }
+ cur_branches = sbmax(sb); /* current no. branches */
+ new_branches = sbmax(sb);
+ del_branches = 0;
+ add_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_ERR
+ "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 lower dentry */
+ tmp_data = kcalloc(max_branches,
+ sizeof(struct unionfs_data), GFP_KERNEL);
+ if (unlikely(!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 (unlikely(!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(KERN_ERR "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(KERN_ERR "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_ERR
+ "unionfs: unrecognized option \"%s\"\n", optname);
+ goto out_release;
+ }
+
+out_no_change:
+
+ /******************************************************************
+ * WE'RE ALMOST DONE: check if leftmost branch might be read-only,
+ * 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 pages that will
+ * have to be re-read.
+ *******************************************************************/
+
+ if (!(tmp_data[0].branchperms & MAY_WRITE)) {
+ printk(KERN_ERR "unionfs: leftmost branch cannot be read-only "
+ "(use \"remount,ro\" to create a read-only union)\n");
+ err = -EINVAL;
+ goto out_release;
+ }
+
+ /* (re)allocate space for new pointers to lower dentry */
+ size = new_branches * sizeof(struct unionfs_data);
+ new_data = krealloc(tmp_data, size, GFP_KERNEL);
+ if (unlikely(!new_data)) {
+ err = -ENOMEM;
+ goto out_release;
+ }
+
+ /* allocate space for new pointers to lower paths */
+ size = new_branches * sizeof(struct path);
+ new_lower_paths = krealloc(tmp_lower_paths, size, GFP_KERNEL);
+ if (unlikely(!new_lower_paths)) {
+ err = -ENOMEM;
+ goto out_release;
+ }
+
+ /* allocate space for new pointers to lower inodes */
+ new_lower_inodes = kcalloc(new_branches,
+ sizeof(struct inode *), GFP_KERNEL);
+ if (unlikely(!new_lower_inodes)) {
+ err = -ENOMEM;
+ goto out_release;
+ }
+
+ /*
+ * 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).
+ */
+
+ /*
+ * Once we finish the remounting successfully, our superblock
+ * generation number will have increased. This will be detected by
+ * our dentry-revalidation code upon subsequent f/s operations
+ * through unionfs. The revalidation code will rebuild the union of
+ * lower inodes for a given unionfs inode and invalidate any pages
+ * of such "stale" inodes (by calling our purge_inode_data
+ * function). This revalidation will happen lazily and
+ * incrementally, as users perform operations on cached inodes. We
+ * would like to encourage this revalidation to happen sooner if
+ * possible, so we try to invalidate as many other pages in our
+ * superblock as we can.
+ */
+ purge_sb_data(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);
+ old_ibstart = ibstart(sb->s_root->d_inode);
+ old_ibend = ibend(sb->s_root->d_inode);
+ ibend(sb->s_root->d_inode) = new_branches - 1;
+ UNIONFS_D(sb->s_root)->bcount = new_branches;
+ new_branches = i; /* no. of branches to release below */
+
+ /*
+ * Update lower inodes: 3 steps
+ * 1. grab ref on all new lower inodes
+ */
+ for (i = dbstart(sb->s_root); i <= dbend(sb->s_root); i++) {
+ struct dentry *lower_dentry =
+ unionfs_lower_dentry_idx(sb->s_root, i);
+ igrab(lower_dentry->d_inode);
+ new_lower_inodes[i] = lower_dentry->d_inode;
+ }
+ /* 2. release reference on all older lower inodes */
+ for (i = old_ibstart; i <= old_ibend; i++) {
+ iput(unionfs_lower_inode_idx(sb->s_root->d_inode, i));
+ unionfs_set_lower_inode_idx(sb->s_root->d_inode, i, NULL);
+ }
+ kfree(UNIONFS_I(sb->s_root->d_inode)->lower_inodes);
+ /* 3. update root dentry's inode to new lower_inodes array */
+ UNIONFS_I(sb->s_root->d_inode)->lower_inodes = new_lower_inodes;
+ new_lower_inodes = NULL;
+
+ /* 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);
+ if (!(*flags & MS_SILENT))
+ pr_info("unionfs: new generation number %d\n", i);
+ /* finally, update the root dentry's times */
+ unionfs_copy_attr_times(sb->s_root->d_inode);
+ 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);
+ kfree(new_lower_inodes);
+out_error:
+ unionfs_check_dentry(sb->s_root);
+ unionfs_write_unlock(sb);
+ return err;
+}
+
+/*
+ * Called by iput() when the inode reference count reached zero
+ * and the inode is not hashed anywhere. Used to clear anything
+ * that needs to be, before the inode is completely destroyed and put
+ * on the inode free list.
+ *
+ * No need to lock sb info's rwsem.
+ */
+static void unionfs_clear_inode(struct inode *inode)
+{
+ int bindex, bstart, bend;
+ struct inode *lower_inode;
+ struct list_head *pos, *n;
+ struct unionfs_dir_state *rdstate;
+
+ list_for_each_safe(pos, n, &UNIONFS_I(inode)->readdircache) {
+ rdstate = list_entry(pos, struct unionfs_dir_state, cache);
+ list_del(&rdstate->cache);
+ free_rdstate(rdstate);
+ }
+
+ /*
+ * Decrement a reference to a lower_inode, which was incremented
+ * by our read_inode when it was created initially.
+ */
+ bstart = ibstart(inode);
+ bend = ibend(inode);
+ if (bstart >= 0) {
+ for (bindex = bstart; bindex <= bend; bindex++) {
+ lower_inode = unionfs_lower_inode_idx(inode, bindex);
+ if (!lower_inode)
+ continue;
+ unionfs_set_lower_inode_idx(inode, bindex, NULL);
+ /* see Documentation/filesystems/unionfs/issues.txt */
+ lockdep_off();
+ iput(lower_inode);
+ lockdep_on();
+ }
+ }
+
+ kfree(UNIONFS_I(inode)->lower_inodes);
+ UNIONFS_I(inode)->lower_inodes = NULL;
+}
+
+static struct inode *unionfs_alloc_inode(struct super_block *sb)
+{
+ struct unionfs_inode_info *i;
+
+ i = kmem_cache_alloc(unionfs_inode_cachep, GFP_KERNEL);
+ if (unlikely(!i))
+ return NULL;
+
+ /* memset everything up to the inode to 0 */
+ memset(i, 0, offsetof(struct unionfs_inode_info, vfs_inode));
+
+ i->vfs_inode.i_version = 1;
+ return &i->vfs_inode;
+}
+
+static void unionfs_destroy_inode(struct inode *inode)
+{
+ kmem_cache_free(unionfs_inode_cachep, UNIONFS_I(inode));
+}
+
+/* unionfs inode cache constructor */
+static void init_once(struct kmem_cache *cachep, void *obj)
+{
+ struct unionfs_inode_info *i = obj;
+
+ inode_init_once(&i->vfs_inode);
+}
+
+int unionfs_init_inode_cache(void)
+{
+ int err = 0;
+
+ unionfs_inode_cachep =
+ kmem_cache_create("unionfs_inode_cache",
+ sizeof(struct unionfs_inode_info), 0,
+ SLAB_RECLAIM_ACCOUNT, init_once);
+ if (unlikely(!unionfs_inode_cachep))
+ err = -ENOMEM;
+ return err;
+}
+
+/* unionfs inode cache destructor */
+void unionfs_destroy_inode_cache(void)
+{
+ if (unionfs_inode_cachep)
+ kmem_cache_destroy(unionfs_inode_cachep);
+}
+
+/*
+ * Called when we have a dirty inode, right here we only throw out
+ * parts of our readdir list that are too old.
+ *
+ * No need to grab sb info's rwsem.
+ */
+static int unionfs_write_inode(struct inode *inode, int sync)
+{
+ struct list_head *pos, *n;
+ struct unionfs_dir_state *rdstate;
+
+ spin_lock(&UNIONFS_I(inode)->rdlock);
+ list_for_each_safe(pos, n, &UNIONFS_I(inode)->readdircache) {
+ rdstate = list_entry(pos, struct unionfs_dir_state, cache);
+ /* We keep this list in LRU order. */
+ if ((rdstate->access + RDCACHE_JIFFIES) > jiffies)
+ break;
+ UNIONFS_I(inode)->rdcount--;
+ list_del(&rdstate->cache);
+ free_rdstate(rdstate);
+ }
+ spin_unlock(&UNIONFS_I(inode)->rdlock);
+
+ return 0;
+}
+
+/*
+ * Used only in nfs, to kill any pending RPC tasks, so that subsequent
+ * code can actually succeed and won't leave tasks that need handling.
+ */
+static void unionfs_umount_begin(struct vfsmount *mnt, int flags)
+{
+ struct super_block *sb, *lower_sb;
+ struct vfsmount *lower_mnt;
+ int bindex, bstart, bend;
+
+ if (!(flags & MNT_FORCE))
+ /*
+ * we are not being MNT_FORCE'd, therefore we should emulate
+ * old behavior
+ */
+ return;
+
+ sb = mnt->mnt_sb;
+
+ unionfs_read_lock(sb, UNIONFS_SMUTEX_CHILD);
+
+ bstart = sbstart(sb);
+ bend = sbend(sb);
+ for (bindex = bstart; bindex <= bend; bindex++) {
+ lower_mnt = unionfs_lower_mnt_idx(sb->s_root, bindex);
+ lower_sb = unionfs_lower_super_idx(sb, bindex);
+
+ if (lower_mnt && lower_sb && lower_sb->s_op &&
+ lower_sb->s_op->umount_begin)
+ lower_sb->s_op->umount_begin(lower_mnt, flags);
+ }
+
+ unionfs_read_unlock(sb);
+}
+
+static int unionfs_show_options(struct seq_file *m, struct vfsmount *mnt)
+{
+ struct super_block *sb = mnt->mnt_sb;
+ int ret = 0;
+ char *tmp_page;
+ char *path;
+ int bindex, bstart, bend;
+ int perms;
+
+ unionfs_read_lock(sb, UNIONFS_SMUTEX_CHILD);
+
+ unionfs_lock_dentry(sb->s_root, UNIONFS_DMUTEX_CHILD);
+
+ tmp_page = (char *) __get_free_page(GFP_KERNEL);
+ if (unlikely(!tmp_page)) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ bstart = sbstart(sb);
+ bend = sbend(sb);
+
+ seq_printf(m, ",dirs=");
+ for (bindex = bstart; bindex <= bend; bindex++) {
+ path = d_path(unionfs_lower_dentry_idx(sb->s_root, bindex),
+ unionfs_lower_mnt_idx(sb->s_root, bindex),
+ tmp_page, PAGE_SIZE);
+ if (IS_ERR(path)) {
+ ret = PTR_ERR(path);
+ goto out;
+ }
+
+ perms = branchperms(sb, bindex);
+
+ seq_printf(m, "%s=%s", path,
+ perms & MAY_WRITE ? "rw" : "ro");
+ if (bindex != bend)
+ seq_printf(m, ":");
+ }
+
+out:
+ free_page((unsigned long) tmp_page);
+
+ unionfs_unlock_dentry(sb->s_root);
+
+ unionfs_read_unlock(sb);
+
+ return ret;
+}
+
+struct super_operations unionfs_sops = {
+ .read_inode = unionfs_read_inode,
+ .delete_inode = unionfs_delete_inode,
+ .put_super = unionfs_put_super,
+ .statfs = unionfs_statfs,
+ .remount_fs = unionfs_remount_fs,
+ .clear_inode = unionfs_clear_inode,
+ .umount_begin = unionfs_umount_begin,
+ .show_options = unionfs_show_options,
+ .write_inode = unionfs_write_inode,
+ .alloc_inode = unionfs_alloc_inode,
+ .destroy_inode = unionfs_destroy_inode,
+};
--
1.5.2.2


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