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Message-Id: <12013239032119-git-send-email-ezk@cs.sunysb.edu>
Date: Sat, 26 Jan 2008 00:04:59 -0500
From: Erez Zadok <ezk@...sunysb.edu>
To: akpm@...ux-foundation.org
Cc: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
viro@....linux.org.uk, hch@...radead.org,
Erez Zadok <ezk@...sunysb.edu>
Subject: [PATCH 1/4] Unionfs: use first writable branch (fix/cleanup)
Cleanup code in ->create, ->symlink, and ->mknod: refactor common code into
helper functions. Also, this allows writing to multiple branches again,
which was broken by an earlier patch.
Signed-off-by: Erez Zadok <ezk@...sunysb.edu>
---
fs/unionfs/inode.c | 395 +++++++++++++++++++++-------------------------------
1 files changed, 156 insertions(+), 239 deletions(-)
diff --git a/fs/unionfs/inode.c b/fs/unionfs/inode.c
index e15ddb9..0b92da2 100644
--- a/fs/unionfs/inode.c
+++ b/fs/unionfs/inode.c
@@ -18,14 +18,159 @@
#include "union.h"
+/*
+ * Helper function when creating new objects (create, symlink, and mknod).
+ * Checks to see if there's a whiteout in @lower_dentry's parent directory,
+ * whose name is taken from @dentry. Then tries to remove that whiteout, if
+ * found.
+ *
+ * Return 0 if no whiteout was found, or if one was found and successfully
+ * removed (a zero tells the caller that @lower_dentry belongs to a good
+ * branch to create the new object in). Return -ERRNO if an error occurred
+ * during whiteout lookup or in trying to unlink the whiteout.
+ */
+static int check_for_whiteout(struct dentry *dentry,
+ struct dentry *lower_dentry)
+{
+ int err = 0;
+ struct dentry *wh_dentry = NULL;
+ struct dentry *lower_dir_dentry;
+ char *name = NULL;
+
+ /*
+ * check if whiteout exists in this branch, i.e. lookup .wh.foo
+ * first.
+ */
+ name = alloc_whname(dentry->d_name.name, dentry->d_name.len);
+ if (unlikely(IS_ERR(name))) {
+ err = PTR_ERR(name);
+ goto out;
+ }
+
+ wh_dentry = lookup_one_len(name, lower_dentry->d_parent,
+ dentry->d_name.len + UNIONFS_WHLEN);
+ if (IS_ERR(wh_dentry)) {
+ err = PTR_ERR(wh_dentry);
+ wh_dentry = NULL;
+ goto out;
+ }
+
+ if (!wh_dentry->d_inode) /* no whiteout exists */
+ goto out;
+
+ /* .wh.foo has been found, so let's unlink it */
+ lower_dir_dentry = lock_parent_wh(wh_dentry);
+ /* see Documentation/filesystems/unionfs/issues.txt */
+ lockdep_off();
+ err = vfs_unlink(lower_dir_dentry->d_inode, wh_dentry);
+ lockdep_on();
+ unlock_dir(lower_dir_dentry);
+
+ /*
+ * Whiteouts are special files and should be deleted no matter what
+ * (as if they never existed), in order to allow this create
+ * operation to succeed. This is especially important in sticky
+ * directories: a whiteout may have been created by one user, but
+ * the newly created file may be created by another user.
+ * Therefore, in order to maintain Unix semantics, if the vfs_unlink
+ * above failed, then we have to try to directly unlink the
+ * whiteout. Note: in the ODF version of unionfs, whiteout are
+ * handled much more cleanly.
+ */
+ if (err == -EPERM) {
+ struct inode *inode = lower_dir_dentry->d_inode;
+ err = inode->i_op->unlink(inode, wh_dentry);
+ }
+ if (err)
+ printk(KERN_ERR "unionfs: could not "
+ "unlink whiteout, err = %d\n", err);
+
+out:
+ dput(wh_dentry);
+ kfree(name);
+ return err;
+}
+
+/*
+ * Find a writeable branch to create new object in. Checks all writeble
+ * branches of the parent inode, from istart to iend order; if none are
+ * suitable, also tries branch 0 (which may require a copyup).
+ *
+ * Return a lower_dentry we can use to create object in, or ERR_PTR.
+ */
+static struct dentry *find_writeable_branch(struct inode *parent,
+ struct dentry *dentry)
+{
+ int err = -EINVAL;
+ int bindex, istart, iend;
+ struct dentry *lower_dentry = NULL;
+
+ istart = ibstart(parent);
+ iend = ibend(parent);
+ if (istart < 0)
+ goto out;
+
+begin:
+ for (bindex = istart; bindex <= iend; bindex++) {
+ /* skip non-writeable branches */
+ err = is_robranch_super(dentry->d_sb, bindex);
+ if (err) {
+ err = -EROFS;
+ continue;
+ }
+ lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
+ if (!lower_dentry)
+ continue;
+ /*
+ * check for whiteouts in writeable branch, and remove them
+ * if necessary.
+ */
+ err = check_for_whiteout(dentry, lower_dentry);
+ if (err)
+ continue;
+ }
+ /*
+ * If istart wasn't already branch 0, and we got any error, then try
+ * branch 0 (which may require copyup)
+ */
+ if (err && istart > 0) {
+ istart = iend = 0;
+ goto begin;
+ }
+
+ /*
+ * If we tried even branch 0, and still got an error, abort. But if
+ * the error was an EROFS, then we should try to copyup.
+ */
+ if (err && err != -EROFS)
+ goto out;
+
+ /*
+ * If we get here, then check if copyup needed. If lower_dentry is
+ * NULL, create the entire dentry directory structure in branch 0.
+ */
+ if (!lower_dentry) {
+ bindex = 0;
+ lower_dentry = create_parents(parent, dentry,
+ dentry->d_name.name, bindex);
+ if (IS_ERR(lower_dentry)) {
+ err = PTR_ERR(lower_dentry);
+ goto out;
+ }
+ }
+ err = 0; /* all's well */
+out:
+ if (err)
+ return ERR_PTR(err);
+ return lower_dentry;
+}
+
static int unionfs_create(struct inode *parent, struct dentry *dentry,
int mode, struct nameidata *nd)
{
int err = 0;
struct dentry *lower_dentry = NULL;
- struct dentry *wh_dentry = NULL;
struct dentry *lower_parent_dentry = NULL;
- char *name = NULL;
int valid = 0;
struct nameidata lower_nd;
@@ -46,89 +191,12 @@ static int unionfs_create(struct inode *parent, struct dentry *dentry,
*/
BUG_ON(!valid && dentry->d_inode);
- /*
- * We shouldn't create things in a read-only branch; this check is a
- * bit redundant as we don't allow branch 0 to be read-only at the
- * moment
- */
- err = is_robranch_super(dentry->d_sb, 0);
- if (err) {
- err = -EROFS;
+ lower_dentry = find_writeable_branch(parent, dentry);
+ if (IS_ERR(lower_dentry)) {
+ err = PTR_ERR(lower_dentry);
goto out;
}
- /*
- * We _always_ create on branch 0
- */
- lower_dentry = unionfs_lower_dentry_idx(dentry, 0);
- if (lower_dentry) {
- /*
- * check if whiteout exists in this branch, i.e. lookup .wh.foo
- * first.
- */
- name = alloc_whname(dentry->d_name.name, dentry->d_name.len);
- if (unlikely(IS_ERR(name))) {
- err = PTR_ERR(name);
- goto out;
- }
-
- wh_dentry = lookup_one_len(name, lower_dentry->d_parent,
- dentry->d_name.len + UNIONFS_WHLEN);
- if (IS_ERR(wh_dentry)) {
- err = PTR_ERR(wh_dentry);
- wh_dentry = NULL;
- goto out;
- }
-
- if (wh_dentry->d_inode) {
- /*
- * .wh.foo has been found, so let's unlink it
- */
- struct dentry *lower_dir_dentry;
-
- lower_dir_dentry = lock_parent_wh(wh_dentry);
- /* see Documentation/filesystems/unionfs/issues.txt */
- lockdep_off();
- err = vfs_unlink(lower_dir_dentry->d_inode, wh_dentry);
- lockdep_on();
- unlock_dir(lower_dir_dentry);
-
- /*
- * Whiteouts are special files and should be deleted
- * no matter what (as if they never existed), in
- * order to allow this create operation to succeed.
- * This is especially important in sticky
- * directories: a whiteout may have been created by
- * one user, but the newly created file may be
- * created by another user. Therefore, in order to
- * maintain Unix semantics, if the vfs_unlink above
- * ailed, then we have to try to directly unlink the
- * whiteout. Note: in the ODF version of unionfs,
- * whiteout are handled much more cleanly.
- */
- if (err == -EPERM) {
- struct inode *inode = lower_dir_dentry->d_inode;
- err = inode->i_op->unlink(inode, wh_dentry);
- }
- if (err) {
- printk(KERN_ERR "unionfs: create: could not "
- "unlink whiteout, err = %d\n", err);
- goto out;
- }
- }
- } else {
- /*
- * if lower_dentry is NULL, create the entire
- * dentry directory structure in branch 0.
- */
- lower_dentry = create_parents(parent, dentry,
- dentry->d_name.name, 0);
- if (IS_ERR(lower_dentry)) {
- err = PTR_ERR(lower_dentry);
- goto out;
- }
- }
-
lower_parent_dentry = lock_parent(lower_dentry);
if (IS_ERR(lower_parent_dentry)) {
err = PTR_ERR(lower_parent_dentry);
@@ -156,9 +224,6 @@ static int unionfs_create(struct inode *parent, struct dentry *dentry,
unlock_dir(lower_parent_dentry);
out:
- dput(wh_dentry);
- kfree(name);
-
if (!err)
unionfs_postcopyup_setmnt(dentry);
@@ -417,86 +482,12 @@ static int unionfs_symlink(struct inode *parent, struct dentry *dentry,
*/
BUG_ON(!valid && dentry->d_inode);
- /*
- * We shouldn't create things in a read-only branch; this check is a
- * bit redundant as we don't allow branch 0 to be read-only at the
- * moment
- */
- err = is_robranch_super(dentry->d_sb, 0);
- if (err) {
- err = -EROFS;
+ lower_dentry = find_writeable_branch(parent, dentry);
+ if (IS_ERR(lower_dentry)) {
+ err = PTR_ERR(lower_dentry);
goto out;
}
- /*
- * We _always_ create on branch 0
- */
- lower_dentry = unionfs_lower_dentry_idx(dentry, 0);
- if (lower_dentry) {
- /*
- * check if whiteout exists in this branch, i.e. lookup .wh.foo
- * first.
- */
- name = alloc_whname(dentry->d_name.name, dentry->d_name.len);
- if (unlikely(IS_ERR(name))) {
- err = PTR_ERR(name);
- goto out;
- }
-
- wh_dentry = lookup_one_len(name, lower_dentry->d_parent,
- dentry->d_name.len + UNIONFS_WHLEN);
- if (IS_ERR(wh_dentry)) {
- err = PTR_ERR(wh_dentry);
- wh_dentry = NULL;
- goto out;
- }
-
- if (wh_dentry->d_inode) {
- /*
- * .wh.foo has been found, so let's unlink it
- */
- struct dentry *lower_dir_dentry;
-
- lower_dir_dentry = lock_parent_wh(wh_dentry);
- err = vfs_unlink(lower_dir_dentry->d_inode, wh_dentry);
- unlock_dir(lower_dir_dentry);
-
- /*
- * Whiteouts are special files and should be deleted
- * no matter what (as if they never existed), in
- * order to allow this create operation to succeed.
- * This is especially important in sticky
- * directories: a whiteout may have been created by
- * one user, but the newly created file may be
- * created by another user. Therefore, in order to
- * maintain Unix semantics, if the vfs_unlink above
- * ailed, then we have to try to directly unlink the
- * whiteout. Note: in the ODF version of unionfs,
- * whiteout are handled much more cleanly.
- */
- if (err == -EPERM) {
- struct inode *inode = lower_dir_dentry->d_inode;
- err = inode->i_op->unlink(inode, wh_dentry);
- }
- if (err) {
- printk(KERN_ERR "unionfs: symlink: could not "
- "unlink whiteout, err = %d\n", err);
- goto out;
- }
- }
- } else {
- /*
- * if lower_dentry is NULL, create the entire
- * dentry directory structure in branch 0.
- */
- lower_dentry = create_parents(parent, dentry,
- dentry->d_name.name, 0);
- if (IS_ERR(lower_dentry)) {
- err = PTR_ERR(lower_dentry);
- goto out;
- }
- }
-
lower_parent_dentry = lock_parent(lower_dentry);
if (IS_ERR(lower_parent_dentry)) {
err = PTR_ERR(lower_parent_dentry);
@@ -713,86 +704,12 @@ static int unionfs_mknod(struct inode *parent, struct dentry *dentry, int mode,
*/
BUG_ON(!valid && dentry->d_inode);
- /*
- * We shouldn't create things in a read-only branch; this check is a
- * bit redundant as we don't allow branch 0 to be read-only at the
- * moment
- */
- err = is_robranch_super(dentry->d_sb, 0);
- if (err) {
- err = -EROFS;
+ lower_dentry = find_writeable_branch(parent, dentry);
+ if (IS_ERR(lower_dentry)) {
+ err = PTR_ERR(lower_dentry);
goto out;
}
- /*
- * We _always_ create on branch 0
- */
- lower_dentry = unionfs_lower_dentry_idx(dentry, 0);
- if (lower_dentry) {
- /*
- * check if whiteout exists in this branch, i.e. lookup .wh.foo
- * first.
- */
- name = alloc_whname(dentry->d_name.name, dentry->d_name.len);
- if (unlikely(IS_ERR(name))) {
- err = PTR_ERR(name);
- goto out;
- }
-
- wh_dentry = lookup_one_len(name, lower_dentry->d_parent,
- dentry->d_name.len + UNIONFS_WHLEN);
- if (IS_ERR(wh_dentry)) {
- err = PTR_ERR(wh_dentry);
- wh_dentry = NULL;
- goto out;
- }
-
- if (wh_dentry->d_inode) {
- /*
- * .wh.foo has been found, so let's unlink it
- */
- struct dentry *lower_dir_dentry;
-
- lower_dir_dentry = lock_parent_wh(wh_dentry);
- err = vfs_unlink(lower_dir_dentry->d_inode, wh_dentry);
- unlock_dir(lower_dir_dentry);
-
- /*
- * Whiteouts are special files and should be deleted
- * no matter what (as if they never existed), in
- * order to allow this create operation to succeed.
- * This is especially important in sticky
- * directories: a whiteout may have been created by
- * one user, but the newly created file may be
- * created by another user. Therefore, in order to
- * maintain Unix semantics, if the vfs_unlink above
- * ailed, then we have to try to directly unlink the
- * whiteout. Note: in the ODF version of unionfs,
- * whiteout are handled much more cleanly.
- */
- if (err == -EPERM) {
- struct inode *inode = lower_dir_dentry->d_inode;
- err = inode->i_op->unlink(inode, wh_dentry);
- }
- if (err) {
- printk(KERN_ERR "unionfs: mknod: could not "
- "unlink whiteout, err = %d\n", err);
- goto out;
- }
- }
- } else {
- /*
- * if lower_dentry is NULL, create the entire
- * dentry directory structure in branch 0.
- */
- lower_dentry = create_parents(parent, dentry,
- dentry->d_name.name, 0);
- if (IS_ERR(lower_dentry)) {
- err = PTR_ERR(lower_dentry);
- goto out;
- }
- }
-
lower_parent_dentry = lock_parent(lower_dentry);
if (IS_ERR(lower_parent_dentry)) {
err = PTR_ERR(lower_parent_dentry);
--
1.5.2.2
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