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Subject[PATCH 71/73] jffs2: Add whiteout support [ver #2]
Date
From: Felix Fietkau <nbd@openwrt.org>

Add support for whiteout dentries to jffs2.

XXX - David Woodhouse suggests several changes and provides an untested patch.
See:

http://patchwork.ozlabs.org/patch/50466/

XXX - Backward compatibility? Creating a whiteout on a JFFS2 file system can
only happen if it is deliberately mounted "-o union" so there is some way to
prevent creation of whiteouts on a file system you want to later mount with an
earlier (no support for whiteout) file system. However, ext2/3 has much more
robust methods (explicit fs feature flag) to prevent such an occurance.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: Valerie Aurora <vaurora@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: linux-mtd@lists.infradead.org
---
fs/jffs2/dir.c | 72 ++++++++++++++++++++++++++++++++++++++++++++++++-
fs/jffs2/fs.c | 4 +++
fs/jffs2/super.c | 2 +
include/linux/jffs2.h | 2 +
4 files changed, 77 insertions(+), 3 deletions(-)
diff --git a/fs/jffs2/dir.c b/fs/jffs2/dir.c
index 973ac58..fe7468d 100644
--- a/fs/jffs2/dir.c
+++ b/fs/jffs2/dir.c
@@ -35,6 +35,8 @@ static int jffs2_mknod (struct inode *,struct dentry *,umode_t,dev_t);
static int jffs2_rename (struct inode *, struct dentry *,
struct inode *, struct dentry *);

+static int jffs2_whiteout (struct inode *, struct dentry *, struct dentry *);
+
const struct file_operations jffs2_dir_operations =
{
.read = generic_read_dir,
@@ -57,6 +59,7 @@ const struct inode_operations jffs2_dir_inode_operations =
.mknod = jffs2_mknod,
.rename = jffs2_rename,
.get_acl = jffs2_get_acl,
+ .whiteout = jffs2_whiteout,
.setattr = jffs2_setattr,
.setxattr = jffs2_setxattr,
.getxattr = jffs2_getxattr,
@@ -97,8 +100,14 @@ static struct dentry *jffs2_lookup(struct inode *dir_i, struct dentry *target,
fd = fd_list;
}
}
- if (fd)
- ino = fd->ino;
+ if (fd) {
+ spin_lock(&target->d_lock);
+ if (fd->type == DT_WHT)
+ target->d_flags |= DCACHE_WHITEOUT;
+ else
+ ino = fd->ino;
+ spin_unlock(&target->d_lock);
+ }
mutex_unlock(&dir_f->sem);
if (ino) {
inode = jffs2_iget(dir_i->i_sb, ino);
@@ -491,6 +500,11 @@ static int jffs2_mkdir (struct inode *dir_i, struct dentry *dentry, umode_t mode
return PTR_ERR(inode);
}

+ if (dentry->d_flags & DCACHE_WHITEOUT) {
+ inode->i_flags |= S_OPAQUE;
+ ri->flags = cpu_to_je16(JFFS2_INO_FLAG_OPAQUE);
+ }
+
inode->i_op = &jffs2_dir_inode_operations;
inode->i_fop = &jffs2_dir_operations;

@@ -769,6 +783,60 @@ static int jffs2_mknod (struct inode *dir_i, struct dentry *dentry, umode_t mode
return ret;
}

+static int jffs2_whiteout (struct inode *dir, struct dentry *old_dentry,
+ struct dentry *new_dentry)
+{
+ struct jffs2_sb_info *c = JFFS2_SB_INFO(dir->i_sb);
+ struct jffs2_inode_info *victim_f = NULL;
+ uint32_t now;
+ int ret;
+
+ /* If it's a directory, then check whether it is really empty */
+ if (new_dentry->d_inode) {
+ victim_f = JFFS2_INODE_INFO(old_dentry->d_inode);
+ if (S_ISDIR(old_dentry->d_inode->i_mode)) {
+ struct jffs2_full_dirent *fd;
+
+ mutex_lock(&victim_f->sem);
+ for (fd = victim_f->dents; fd; fd = fd->next) {
+ if (fd->ino) {
+ mutex_unlock(&victim_f->sem);
+ return -ENOTEMPTY;
+ }
+ }
+ mutex_unlock(&victim_f->sem);
+ }
+ }
+
+ now = get_seconds();
+ ret = jffs2_do_link(c, JFFS2_INODE_INFO(dir), 0, DT_WHT,
+ new_dentry->d_name.name, new_dentry->d_name.len, now);
+ if (ret)
+ return ret;
+
+ spin_lock(&new_dentry->d_lock);
+ new_dentry->d_flags |= DCACHE_WHITEOUT;
+ spin_unlock(&new_dentry->d_lock);
+ d_add(new_dentry, NULL);
+
+ if (victim_f) {
+ /* There was a victim. Kill it off nicely */
+ drop_nlink(old_dentry->d_inode);
+ /* Don't oops if the victim was a dirent pointing to an
+ inode which didn't exist. */
+ if (victim_f->inocache) {
+ mutex_lock(&victim_f->sem);
+ if (S_ISDIR(old_dentry->d_inode->i_mode))
+ victim_f->inocache->pino_nlink = 0;
+ else
+ victim_f->inocache->pino_nlink--;
+ mutex_unlock(&victim_f->sem);
+ }
+ }
+
+ return 0;
+}
+
static int jffs2_rename (struct inode *old_dir_i, struct dentry *old_dentry,
struct inode *new_dir_i, struct dentry *new_dentry)
{
diff --git a/fs/jffs2/fs.c b/fs/jffs2/fs.c
index 2e01238..b286ce5 100644
--- a/fs/jffs2/fs.c
+++ b/fs/jffs2/fs.c
@@ -303,6 +303,10 @@ struct inode *jffs2_iget(struct super_block *sb, unsigned long ino)

inode->i_op = &jffs2_dir_inode_operations;
inode->i_fop = &jffs2_dir_operations;
+
+ if (je16_to_cpu(latest_node.flags) & JFFS2_INO_FLAG_OPAQUE)
+ inode->i_flags |= S_OPAQUE;
+
break;
}
case S_IFREG:
diff --git a/fs/jffs2/super.c b/fs/jffs2/super.c
index f2d96b5..9fb059a 100644
--- a/fs/jffs2/super.c
+++ b/fs/jffs2/super.c
@@ -295,7 +295,7 @@ static int jffs2_fill_super(struct super_block *sb, void *data, int silent)

sb->s_op = &jffs2_super_operations;
sb->s_export_op = &jffs2_export_ops;
- sb->s_flags = sb->s_flags | MS_NOATIME;
+ sb->s_flags = sb->s_flags | MS_NOATIME | MS_WHITEOUT;
sb->s_xattr = jffs2_xattr_handlers;
#ifdef CONFIG_JFFS2_FS_POSIX_ACL
sb->s_flags |= MS_POSIXACL;
diff --git a/include/linux/jffs2.h b/include/linux/jffs2.h
index a18b719..6404e01 100644
--- a/include/linux/jffs2.h
+++ b/include/linux/jffs2.h
@@ -88,6 +88,8 @@
#define JFFS2_INO_FLAG_USERCOMPR 2 /* User has requested a specific
compression type */

+#define JFFS2_INO_FLAG_OPAQUE 4 /* Directory is opaque (for union mounts) */
+

/* These can go once we've made sure we've caught all uses without
byteswapping */


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