Re: [PATCH 04/22][RFC] Unionfs: Common file operations

Trond Myklebust
2006-09-01T22:20:21Z

On Thu, 2006-08-31 at 21:41 -0400, Josef Sipek wrote:
> From: David Quigley <dquigley@fsl.cs.sunysb.edu>
>
> This patch contains helper functions used through the rest of the code which
> pertains to files.
>
> Signed-off-by: David Quigley <dquigley@fsl.cs.sunysb.edu>
> Signed-off-by: Josef "Jeff" Sipek <jsipek@cs.sunysb.edu>
> Signed-off-by: Erez Zadok <ezk@cs.sunysb.edu>
>
> ---
>
> fs/unionfs/commonfops.c | 575 ++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 575 insertions(+)
>
> diff -Nur -x linux-2.6-git/Documentation/dontdiff linux-2.6-git/fs/unionfs/commonfops.c linux-2.6-git-unionfs/fs/unionfs/commonfops.c
> --- linux-2.6-git/fs/unionfs/commonfops.c 1969-12-31 19:00:00.000000000 -0500
> +++ linux-2.6-git-unionfs/fs/unionfs/commonfops.c 2006-08-31 19:04:00.000000000 -0400
> @@ -0,0 +1,575 @@
> +/*
> + * 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"
> +
> +/* 1) Copyup the file
> + * 2) Rename the file to '.unionfs<original inode#><counter>' - obviously
> + * stolen from NFS's silly rename
> + */
> +static int copyup_deleted_file(struct file *file, struct dentry *dentry,
> + int bstart, int bindex)
> +{
> + static unsigned int counter;
> + const int i_inosize = sizeof(dentry->d_inode->i_ino) * 2;
> + const int countersize = sizeof(counter) * 2;
> + const int nlen = sizeof(".unionfs") + i_inosize + countersize - 1;
> + char name[nlen + 1];
> +
> + int err;
> + struct dentry *tmp_dentry = NULL;
> + struct dentry *hidden_dentry = NULL;
> + struct dentry *hidden_dir_dentry = NULL;
> +
> + hidden_dentry = dtohd_index(dentry, bstart);
> +
> + sprintf(name, ".unionfs%*.*lx",
> + i_inosize, i_inosize, hidden_dentry->d_inode->i_ino);
> +
> + tmp_dentry = NULL;
> + do {
> + char *suffix = name + nlen - countersize;
> +
> + dput(tmp_dentry);
> + counter++;
> + sprintf(suffix, "%*.*x", countersize, countersize, counter);
> +
> + printk(KERN_DEBUG "unionfs: trying to rename %s to %s\n",
> + dentry->d_name.name, name);
> +
> + tmp_dentry = lookup_one_len(name, hidden_dentry->d_parent,
> + UNIONFS_TMPNAM_LEN);
> + if (IS_ERR(tmp_dentry)) {
> + err = PTR_ERR(tmp_dentry);
> + goto out;
> + }
> + } while (tmp_dentry->d_inode != NULL); /* need negative dentry */
> +
> + err = copyup_named_file(dentry->d_parent->d_inode, file, name, bstart,
> + bindex, file->f_dentry->d_inode->i_size);
> + if (err)
> + goto out;
> +
> + /* bring it to the same state as an unlinked file */
> + hidden_dentry = dtohd_index(dentry, dbstart(dentry));
> + hidden_dir_dentry = lock_parent(hidden_dentry);
> + err = vfs_unlink(hidden_dir_dentry->d_inode, hidden_dentry);
> + unlock_dir(hidden_dir_dentry);
> +
> +out:
> + return err;
> +}
> +
> +static void cleanup_file(struct file *file, struct dentry *dentry)
> +{
> + int bindex, bstart, bend;
> +
> + bstart = fbstart(file);
> + bend = fbend(file);
> + for (bindex = bstart; bindex <= bend; bindex++) {
> + if (ftohf_index(file, bindex)) {
> + branchput(dentry->d_sb, bindex);
> + fput(ftohf_index(file, bindex));
> + }
> + }
> +
> + if (ftohf_ptr(file)) {
> + kfree(ftohf_ptr(file));
> + ftohf_ptr(file) = NULL;
> + }
> +}
> +
> +static int open_all_files(struct file *file, struct dentry *dentry)
> +{
> + int bindex, bstart, bend, err = 0;
> + struct file *hidden_file;
> + struct dentry *hidden_dentry;
> + struct super_block *sb = dentry->d_sb;
> +
> + bstart = dbstart(dentry);
> + bend = dbend(dentry);
> +
> + for (bindex = bstart; bindex <= bend; bindex++) {
> + hidden_dentry = dtohd_index(dentry, bindex);
> + if (!hidden_dentry)
> + continue;
> +
> + dget(hidden_dentry);
> + mntget(stohiddenmnt_index(sb, bindex));
> + branchget(sb, bindex);
> +
> + hidden_file = dentry_open(hidden_dentry,
> + stohiddenmnt_index(sb, bindex), file->f_flags);
> + if (IS_ERR(hidden_file)) {
> + err = PTR_ERR(hidden_file);
> + goto out;
> + } else
> + set_ftohf_index(file, bindex, hidden_file);
> + }
> +out:
> + return err;
> +}
> +
> +static int open_highest_file(struct file *file, struct dentry *dentry,
> + int willwrite)
> +{
> + int bindex, bstart, bend, err = 0;
> + struct file *hidden_file;
> + struct dentry *hidden_dentry;
> + struct inode *parent_inode = dentry->d_parent->d_inode;
> + size_t inode_size = file->f_dentry->d_inode->i_size;
> + struct super_block *sb = dentry->d_sb;
> +
> + bstart = dbstart(dentry);
> + bend = dbend(dentry);
> +
> + hidden_dentry = dtohd(dentry);
> + if (willwrite && IS_WRITE_FLAG(file->f_flags)
> + && is_robranch(dentry)) {
> + for (bindex = bstart - 1; bindex >= 0; bindex--) {
> + err = copyup_file(parent_inode, file, bstart, bindex,
> + inode_size);
> + if (!err)
> + break;
> +
> + }
> + atomic_set(&ftopd(file)->ufi_generation,
> + atomic_read(&itopd(dentry->d_inode)->uii_generation));
> + goto out;
> + }
> +
> + dget(hidden_dentry);
> + mntget(stohiddenmnt_index(sb, bstart));
> + branchget(sb, bstart);
> + hidden_file = dentry_open(hidden_dentry,
> + stohiddenmnt_index(sb, bstart), file->f_flags);
> + if (IS_ERR(hidden_file)) {
> + err = PTR_ERR(hidden_file);
> + goto out;
> + }
> + set_ftohf(file, hidden_file);
> + /* Fix up the position. */
> + hidden_file->f_pos = file->f_pos;
> +
> + memcpy(&(hidden_file->f_ra), &(file->f_ra),
> + sizeof(struct file_ra_state));
> +out:
> + return err;
> +}
> +
> +static int do_delayed_copyup(struct file *file, struct dentry *dentry)
> +{
> + int bindex, bstart, bend, err = 0;
> + struct inode *parent_inode = dentry->d_parent->d_inode;
> + size_t inode_size = file->f_dentry->d_inode->i_size;
> +
> + bstart = fbstart(file);
> + bend = fbend(file);
> +
> + BUG_ON(!S_ISREG(file->f_dentry->d_inode->i_mode));
> +
> + for (bindex = bstart - 1; bindex >= 0; bindex--) {
> + if (!d_deleted(file->f_dentry))
> + err = copyup_file(parent_inode, file, bstart,
> + bindex, inode_size);
> + else
> + err = copyup_deleted_file(file, dentry, bstart, bindex);
> +
> + if (!err)
> + break;
> + }
> + if (!err && (bstart > fbstart(file))) {
> + bend = fbend(file);
> + for (bindex = bstart; bindex <= bend; bindex++) {
> + if (ftohf_index(file, bindex)) {
> + branchput(dentry->d_sb, bindex);
> + fput(ftohf_index(file, bindex));
> + set_ftohf_index(file, bindex, NULL);
> + }
> + }
> + fbend(file) = bend;
> + }
> + return err;
> +}
> +
> +int unionfs_file_revalidate(struct file *file, int willwrite)
> +{
> + struct super_block *sb;
> + struct dentry *dentry;
> + int sbgen, fgen, dgen;
> + int bstart, bend;
> + int size;
> +
> + int err = 0;
> +
> + dentry = file->f_dentry;
> + lock_dentry(dentry);
> + sb = dentry->d_sb;
> + unionfs_read_lock(sb);
> + if (!unionfs_d_revalidate(dentry, NULL) && !d_deleted(dentry)) {
> + err = -ESTALE;
> + goto out;
> + }
> +
> + sbgen = atomic_read(&stopd(sb)->usi_generation);
> + dgen = atomic_read(&dtopd(dentry)->udi_generation);
> + fgen = atomic_read(&ftopd(file)->ufi_generation);
> +
> + BUG_ON(sbgen > dgen);
> +
> + /* There are two cases we are interested in. The first is if the
> + * generation is lower than the super-block. The second is if someone
> + * has copied up this file from underneath us, we also need to refresh
> + * things. */
> + if (!d_deleted(dentry) &&
> + ((sbgen > fgen) || (dbstart(dentry) != fbstart(file)))) {
> + /* First we throw out the existing files. */
> + cleanup_file(file, dentry);
> +
> + /* Now we reopen the file(s) as in unionfs_open. */
> + bstart = fbstart(file) = dbstart(dentry);
> + bend = fbend(file) = dbend(dentry);
> +
> + size = sizeof(struct file *) * sbmax(sb);
> + ftohf_ptr(file) = kzalloc(size, GFP_KERNEL);
> + if (!ftohf_ptr(file)) {
> + err = -ENOMEM;
> + goto out;
> + }
> +
> + if (S_ISDIR(dentry->d_inode->i_mode)) {
> + /* We need to open all the files. */
> + err = open_all_files(file, dentry);
> + if (err)
> + goto out;
> + } else {
> + /* We only open the highest priority branch. */
> + err = open_highest_file(file, dentry, willwrite);
> + if (err)
> + goto out;
> + }
> + atomic_set(&ftopd(file)->ufi_generation,
> + atomic_read(&itopd(dentry->d_inode)->
> + uii_generation));
> + }
> +
> + /* Copyup on the first write to a file on a readonly branch. */
> + if (willwrite && IS_WRITE_FLAG(file->f_flags)
> + && !IS_WRITE_FLAG(ftohf(file)->f_flags) && is_robranch(dentry)) {
> + printk(KERN_DEBUG
> + "Doing delayed copyup of a read-write file on a read-only branch.\n");
> + err = do_delayed_copyup(file, dentry);
> + }
> +
> +out:
> + unlock_dentry(dentry);
> + unionfs_read_unlock(dentry->d_sb);
> + return err;
> +}
> +
> +/* unionfs_open helper function: open a directory */
> +static inline int __open_dir(struct inode *inode, struct file *file)
> +{
> + struct dentry *hidden_dentry;
> + struct file *hidden_file;
> + int bindex, bstart, bend;
> +
> + bstart = fbstart(file) = dbstart(file->f_dentry);
> + bend = fbend(file) = dbend(file->f_dentry);
> +
> + for (bindex = bstart; bindex <= bend; bindex++) {
> + hidden_dentry = dtohd_index(file->f_dentry, bindex);
> + if (!hidden_dentry)
> + continue;
> +
> + dget(hidden_dentry);
> + mntget(stohiddenmnt_index(inode->i_sb, bindex));
> + hidden_file = dentry_open(hidden_dentry,
> + stohiddenmnt_index(inode->i_sb, bindex),
> + file->f_flags);

Race! You cannot open an underlying NFS file by name after it has been
looked up: you have no guarantee that it hasn't been renamed.

> + if (IS_ERR(hidden_file))
> + return PTR_ERR(hidden_file);
> +
> + set_ftohf_index(file, bindex, hidden_file);
> +
> + /* The branchget goes after the open, because otherwise
> + * we would miss the reference on release. */
> + branchget(inode->i_sb, bindex);
> + }
> +
> + return 0;
> +}
> +
> +/* unionfs_open helper function: open a file */
> +static inline int __open_file(struct inode *inode, struct file *file)
> +{
> + struct dentry *hidden_dentry;
> + struct file *hidden_file;
> + int hidden_flags;
> + int bindex, bstart, bend;
> +
> + hidden_dentry = dtohd(file->f_dentry);
> + hidden_flags = file->f_flags;
> +
> + bstart = fbstart(file) = dbstart(file->f_dentry);
> + bend = fbend(file) = dbend(file->f_dentry);
> +
> + /* check for the permission for hidden file. If the error is COPYUP_ERR,
> + * copyup the file.
> + */
> + if (hidden_dentry->d_inode && is_robranch(file->f_dentry)) {
> + /* if the open will change the file, copy it up otherwise defer it. */
> + if (hidden_flags & O_TRUNC) {
> + int size = 0;
> + int err = -EROFS;
> +
> + /* copyup the file */
> + for (bindex = bstart - 1; bindex >= 0; bindex--) {
> + err = copyup_file(file->f_dentry->d_parent->d_inode,
> + file, bstart, bindex, size);
> + if (!err)
> + break;
> + }
> + return err;
> + } else
> + hidden_flags &= ~(OPEN_WRITE_FLAGS);
> + }
> +
> + dget(hidden_dentry);
> +
> + /* dentry_open will decrement mnt refcnt if err.
> + * otherwise fput() will do an mntput() for us upon file close.
> + */
> + mntget(stohiddenmnt_index(inode->i_sb, bstart));
> + hidden_file = dentry_open(hidden_dentry,
> + stohiddenmnt_index(inode->i_sb, bstart),
> + hidden_flags);

Race: see above. Besides, calling dentry_open() directly on an NFS file
is a bug!

> + if (IS_ERR(hidden_file))
> + return PTR_ERR(hidden_file);
> +
> + set_ftohf(file, hidden_file);
> + branchget(inode->i_sb, bstart);
> +
> + return 0;
> +}
> +
> +int unionfs_open(struct inode *inode, struct file *file)
> +{
> + int err = 0;
> + struct file *hidden_file = NULL;
> + struct dentry *dentry = NULL;
> + int bindex = 0, bstart = 0, bend = 0;
> + int size;
> +
> + ftopd_lhs(file) = kzalloc(sizeof(struct unionfs_file_info), GFP_KERNEL);
> + if (!ftopd(file)) {
> + err = -ENOMEM;
> + goto out;
> + }
> + fbstart(file) = -1;
> + fbend(file) = -1;
> + atomic_set(&ftopd(file)->ufi_generation,
> + atomic_read(&itopd(inode)->uii_generation));
> +
> + size = sizeof(struct file *) * sbmax(inode->i_sb);
> + ftohf_ptr(file) = kzalloc(size, GFP_KERNEL);
> + if (!ftohf_ptr(file)) {
> + err = -ENOMEM;
> + goto out;
> + }
> +
> + dentry = file->f_dentry;
> + lock_dentry(dentry);
> + unionfs_read_lock(inode->i_sb);
> +
> + bstart = fbstart(file) = dbstart(dentry);
> + bend = fbend(file) = dbend(dentry);
> +
> + /* increment, so that we can flush appropriately */
> + atomic_inc(&itopd(dentry->d_inode)->uii_totalopens);
> +
> + /* open all directories and make the unionfs file struct point to these hidden file structs */
> + if (S_ISDIR(inode->i_mode))
> + err = __open_dir(inode, file); /* open a dir */
> + else
> + err = __open_file(inode, file); /* open a file */
> +
> + /* freeing the allocated resources, and fput the opened files */
> + if (err) {
> + for (bindex = bstart; bindex <= bend; bindex++) {
> + hidden_file = ftohf_index(file, bindex);
> + if (!hidden_file)
> + continue;
> +
> + branchput(file->f_dentry->d_sb, bindex);
> + /* fput calls dput for hidden_dentry */
> + fput(hidden_file);
> + }
> + }
> +
> + unlock_dentry(dentry);
> + unionfs_read_unlock(inode->i_sb);
> +
> +out:
> + if (err) {
> + kfree(ftohf_ptr(file));
> + kfree(ftopd(file));
> + }
> +
> + return err;
> +}
> +
> +int unionfs_file_release(struct inode *inode, struct file *file)
> +{
> + int err = 0;
> + struct file *hidden_file = NULL;
> + int bindex, bstart, bend;
> + int fgen;
> +
> + /* fput all the hidden files */
> + fgen = atomic_read(&ftopd(file)->ufi_generation);
> + bstart = fbstart(file);
> + bend = fbend(file);
> +
> + for (bindex = bstart; bindex <= bend; bindex++) {
> + hidden_file = ftohf_index(file, bindex);
> +
> + if (hidden_file) {
> + fput(hidden_file);
> + unionfs_read_lock(inode->i_sb);
> + branchput(inode->i_sb, bindex);
> + unionfs_read_unlock(inode->i_sb);
> + }
> + }
> + kfree(ftohf_ptr(file));
> +
> + if (ftopd(file)->rdstate) {
> + ftopd(file)->rdstate->uds_access = jiffies;
> + printk(KERN_DEBUG "Saving rdstate with cookie %u [%d.%lld]\n",
> + ftopd(file)->rdstate->uds_cookie,
> + ftopd(file)->rdstate->uds_bindex,
> + (long long)ftopd(file)->rdstate->uds_dirpos);
> + spin_lock(&itopd(inode)->uii_rdlock);
> + itopd(inode)->uii_rdcount++;
> + list_add_tail(&ftopd(file)->rdstate->uds_cache,
> + &itopd(inode)->uii_readdircache);
> + mark_inode_dirty(inode);
> + spin_unlock(&itopd(inode)->uii_rdlock);
> + ftopd(file)->rdstate = NULL;
> + }
> + kfree(ftopd(file));
> + return err;
> +}
> +
> +static inline long do_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
> +{
> + struct file *hidden_file;
> + int err;
> +
> + hidden_file = ftohf(file);
> +
> + err = security_file_ioctl(hidden_file, cmd, arg);
> + if (err)
> + goto out;
> + err = -ENOTTY;
> + if (!hidden_file || !hidden_file->f_op)
> + goto out;
> + if (hidden_file->f_op->unlocked_ioctl) {
> + err = hidden_file->f_op->unlocked_ioctl(hidden_file, cmd, arg);
> + } else if (hidden_file->f_op->ioctl) {
> + lock_kernel();
> + err = hidden_file->f_op->ioctl(hidden_file->f_dentry->d_inode,
> + hidden_file, cmd, arg);
> + unlock_kernel();
> + }
> +
> +out:
> + return err;
> +}
> +
> +long unionfs_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
> +{
> + long err = 0; /* don't fail by default */
> +
> + if ((err = unionfs_file_revalidate(file, 1)))
> + goto out;
> +
> + /* check if asked for local commands */
> + switch (cmd) {
> + case UNIONFS_IOCTL_INCGEN:
> + if (!capable(CAP_SYS_ADMIN)) {
> + err = -EACCES;
> + goto out;
> + }
> + err = unionfs_ioctl_incgen(file, cmd, arg);
> + break;
> +
> + case UNIONFS_IOCTL_QUERYFILE:
> + err = unionfs_ioctl_queryfile(file, cmd, arg);
> + break;
> +
> + default:
> + err = do_ioctl(file, cmd, arg);
> + break;
> + }
> +
> +out:
> + return err;
> +}
> +
> +int unionfs_flush(struct file *file, fl_owner_t id)
> +{
> + int err = 0; /* assume ok (see open.c:close_fp) */
> + struct file *hidden_file = NULL;
> + int bindex, bstart, bend;
> +
> + if ((err = unionfs_file_revalidate(file, 1)))
> + goto out;
> + if (!atomic_dec_and_test
> + (&itopd(file->f_dentry->d_inode)->uii_totalopens))
> + goto out;
> +
> + lock_dentry(file->f_dentry);
> +
> + bstart = fbstart(file);
> + bend = fbend(file);
> + for (bindex = bstart; bindex <= bend; bindex++) {
> + hidden_file = ftohf_index(file, bindex);
> +
> + if (hidden_file && hidden_file->f_op
> + && hidden_file->f_op->flush) {
> + err = hidden_file->f_op->flush(hidden_file, id);
> + if (err)
> + goto out_lock;
> +
> + /* if there are no more references to the dentry, dput it */
> + if (d_deleted(file->f_dentry)) {
> + dput(dtohd_index(file->f_dentry, bindex));
> + set_dtohd_index(file->f_dentry, bindex, NULL);
> + }
> + }
> +
> + }
> +
> +out_lock:
> + unlock_dentry(file->f_dentry);
> +out:
> + return err;
> +}
> +
> -
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--
VGER BF report: H 0.0108304