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List: linux-btrfs
Subject: [PATCH 4/5] btrfs: Add readonly snapshots support
From: Li Zefan <lizf () cn ! fujitsu ! com>
Date: 2010-11-29 8:03:38
Message-ID: 4CF35E5A.6080208 () cn ! fujitsu ! com
[Download RAW message or body]
Usage:
Set BTRFS_SNAPSHOT_CREATE_RDONLY of btrfs_ioctl_vol_arg_v2->flags,
and call ioctl(BTRFS_I0CTL_SNAP_CREATE_V2).
Implementation:
- In disk set readonly bit of btrfs_root_item->flags, and in memory
set btrfs_root->readonly.
- Add readonly checks in btrfs_permission (inode_permission),
btrfs_setattr, btrfs_set/remove_xattr and some ioctls.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
---
fs/btrfs/ctree.h | 3 +++
fs/btrfs/disk-io.c | 5 +++++
fs/btrfs/inode.c | 8 ++++++++
fs/btrfs/ioctl.c | 33 +++++++++++++++++++++++++--------
fs/btrfs/ioctl.h | 1 +
fs/btrfs/transaction.c | 8 ++++++++
fs/btrfs/transaction.h | 1 +
fs/btrfs/xattr.c | 18 ++++++++++++++++++
8 files changed, 69 insertions(+), 8 deletions(-)
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 8db9234..4b263ed 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -597,6 +597,8 @@ struct btrfs_dir_item {
u8 type;
} __attribute__ ((__packed__));
+#define BTRFS_ROOT_SNAP_RDONLY (1ULL << 0)
+
struct btrfs_root_item {
struct btrfs_inode_item inode;
__le64 generation;
@@ -1116,6 +1118,7 @@ struct btrfs_root {
int defrag_running;
char *name;
int in_sysfs;
+ bool readonly;
/* the dirty list is only used by non-reference counted roots */
struct list_head dirty_list;
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index fb650e0..5b88712 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -963,6 +963,7 @@ static void __setup_root_post(struct btrfs_root *root)
{
u32 blocksize;
u64 generation;
+ u64 flags;
generation = btrfs_root_generation(&root->root_item);
blocksize = btrfs_level_size(root, btrfs_root_level(&root->root_item));
@@ -970,6 +971,10 @@ static void __setup_root_post(struct btrfs_root *root)
blocksize, generation);
BUG_ON(!root->node);
root->commit_root = btrfs_root_node(root);
+
+ flags = btrfs_root_flags(&root->root_item);
+ if (flags & BTRFS_ROOT_SNAP_RDONLY)
+ root->readonly = true;
}
static int find_and_setup_root(struct btrfs_root *tree_root,
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 5132c9a..08c3075 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -3671,8 +3671,12 @@ static int btrfs_setattr_size(struct inode *inode, struct iattr *attr)
static int btrfs_setattr(struct dentry *dentry, struct iattr *attr)
{
struct inode *inode = dentry->d_inode;
+ struct btrfs_root *root = BTRFS_I(inode)->root;
int err;
+ if (root->readonly)
+ return -EROFS;
+
err = inode_change_ok(inode, attr);
if (err)
return err;
@@ -7028,6 +7032,10 @@ static int btrfs_set_page_dirty(struct page *page)
static int btrfs_permission(struct inode *inode, int mask)
{
+ struct btrfs_root *root = BTRFS_I(inode)->root;
+
+ if (root->readonly && (mask & MAY_WRITE))
+ return -EROFS;
if ((BTRFS_I(inode)->flags & BTRFS_INODE_READONLY) && (mask & MAY_WRITE))
return -EACCES;
return generic_permission(inode, mask, btrfs_check_acl);
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index ba437ad..7f9c571 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -147,6 +147,9 @@ static int btrfs_ioctl_setflags(struct file *file, void __user *arg)
unsigned int flags, oldflags;
int ret;
+ if (root->readonly)
+ return -EROFS;
+
if (copy_from_user(&flags, arg, sizeof(flags)))
return -EFAULT;
@@ -351,7 +354,8 @@ fail:
}
static int create_snapshot(struct btrfs_root *root, struct dentry *dentry,
- char *name, int namelen, u64 *async_transid)
+ char *name, int namelen, u64 *async_transid,
+ bool readonly)
{
struct inode *inode;
struct btrfs_pending_snapshot *pending_snapshot;
@@ -368,6 +372,7 @@ static int create_snapshot(struct btrfs_root *root, struct dentry *dentry,
btrfs_init_block_rsv(&pending_snapshot->block_rsv);
pending_snapshot->dentry = dentry;
pending_snapshot->root = root;
+ pending_snapshot->readonly = readonly;
trans = btrfs_start_transaction(root->fs_info->extent_root, 5);
if (IS_ERR(trans)) {
@@ -497,7 +502,7 @@ static inline int btrfs_may_create(struct inode *dir, struct dentry *child)
static noinline int btrfs_mksubvol(struct path *parent,
char *name, int namelen,
struct btrfs_root *snap_src,
- u64 *async_transid)
+ u64 *async_transid, bool readonly)
{
struct inode *dir = parent->dentry->d_inode;
struct dentry *dentry;
@@ -529,7 +534,7 @@ static noinline int btrfs_mksubvol(struct path *parent,
if (snap_src) {
error = create_snapshot(snap_src, dentry,
- name, namelen, async_transid);
+ name, namelen, async_transid, readonly);
} else {
error = create_subvol(BTRFS_I(dir)->root, dentry,
name, namelen, async_transid);
@@ -889,7 +894,8 @@ static noinline int btrfs_ioctl_snap_create_transid(struct file *file,
char *name,
unsigned long fd,
int subvol,
- u64 *transid)
+ u64 *transid,
+ bool readonly)
{
struct btrfs_root *root = BTRFS_I(fdentry(file)->d_inode)->root;
struct file *src_file;
@@ -907,7 +913,7 @@ static noinline int btrfs_ioctl_snap_create_transid(struct file *file,
if (subvol) {
ret = btrfs_mksubvol(&file->f_path, name, namelen,
- NULL, transid);
+ NULL, transid, readonly);
} else {
struct inode *src_inode;
src_file = fget(fd);
@@ -926,7 +932,7 @@ static noinline int btrfs_ioctl_snap_create_transid(struct file *file,
}
ret = btrfs_mksubvol(&file->f_path, name, namelen,
BTRFS_I(src_inode)->root,
- transid);
+ transid, readonly);
fput(src_file);
}
out:
@@ -943,6 +949,7 @@ static noinline int btrfs_ioctl_snap_create(struct file *file,
u64 fd;
u64 transid = 0;
bool async = false;
+ bool readonly = false;
int ret;
if (v2) {
@@ -950,7 +957,8 @@ static noinline int btrfs_ioctl_snap_create(struct file *file,
if (IS_ERR(vol_args_v2))
return PTR_ERR(vol_args_v2);
- if (vol_args_v2->flags & ~BTRFS_SNAPSHOT_CREATE_ASYNC) {
+ if (vol_args_v2->flags &
+ ~(BTRFS_SNAPSHOT_CREATE_ASYNC | BTRFS_SNAPSHOT_RDONLY)) {
ret = -EINVAL;
goto out;
}
@@ -960,6 +968,8 @@ static noinline int btrfs_ioctl_snap_create(struct file *file,
vol_args_v2->name[BTRFS_SNAPSHOT_NAME_MAX] = '\0';
if (vol_args_v2->flags & BTRFS_SNAPSHOT_CREATE_ASYNC)
async = true;
+ if (vol_args_v2->flags & BTRFS_SNAPSHOT_RDONLY)
+ readonly = true;
} else {
vol_args = memdup_user(arg, sizeof(*vol_args));
if (IS_ERR(vol_args))
@@ -970,7 +980,7 @@ static noinline int btrfs_ioctl_snap_create(struct file *file,
}
ret = btrfs_ioctl_snap_create_transid(file, name, fd,
- subvol, &transid);
+ subvol, &transid, readonly);
if (!ret && async) {
if (copy_to_user(arg +
@@ -1621,6 +1631,9 @@ static noinline long btrfs_ioctl_clone(struct file *file, unsigned long srcfd,
if (!(file->f_mode & FMODE_WRITE) || (file->f_flags & O_APPEND))
return -EINVAL;
+ if (root->readonly)
+ return -EROFS;
+
ret = mnt_want_write(file->f_path.mnt);
if (ret)
return ret;
@@ -1943,6 +1956,10 @@ static long btrfs_ioctl_trans_start(struct file *file)
if (file->private_data)
goto out;
+ ret = -EROFS;
+ if (root->readonly)
+ goto out;
+
ret = mnt_want_write(file->f_path.mnt);
if (ret)
goto out;
diff --git a/fs/btrfs/ioctl.h b/fs/btrfs/ioctl.h
index bc70584..ff15fb2 100644
--- a/fs/btrfs/ioctl.h
+++ b/fs/btrfs/ioctl.h
@@ -31,6 +31,7 @@ struct btrfs_ioctl_vol_args {
};
#define BTRFS_SNAPSHOT_CREATE_ASYNC (1ULL << 0)
+#define BTRFS_SNAPSHOT_RDONLY (1ULL << 1)
#define BTRFS_SNAPSHOT_NAME_MAX 4039
struct btrfs_ioctl_vol_args_v2 {
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 1fffbc0..fe85149 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -909,6 +909,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
u64 to_reserve = 0;
u64 index = 0;
u64 objectid;
+ u64 root_flags;
new_root_item = kmalloc(sizeof(*new_root_item), GFP_NOFS);
if (!new_root_item) {
@@ -965,6 +966,13 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
btrfs_set_root_last_snapshot(&root->root_item, trans->transid);
memcpy(new_root_item, &root->root_item, sizeof(*new_root_item));
+ root_flags = btrfs_root_flags(new_root_item);
+ if (pending->readonly)
+ root_flags |= BTRFS_ROOT_SNAP_RDONLY;
+ else
+ root_flags &= ~BTRFS_ROOT_SNAP_RDONLY;
+ btrfs_set_root_flags(new_root_item, root_flags);
+
old = btrfs_lock_root_node(root);
btrfs_cow_block(trans, root, old, NULL, 0, &old);
btrfs_set_lock_blocking(old);
diff --git a/fs/btrfs/transaction.h b/fs/btrfs/transaction.h
index f104b57..229a594 100644
--- a/fs/btrfs/transaction.h
+++ b/fs/btrfs/transaction.h
@@ -62,6 +62,7 @@ struct btrfs_pending_snapshot {
struct btrfs_block_rsv block_rsv;
/* extra metadata reseration for relocation */
int error;
+ bool readonly;
struct list_head list;
};
diff --git a/fs/btrfs/xattr.c b/fs/btrfs/xattr.c
index 698fdd2..858ad4a 100644
--- a/fs/btrfs/xattr.c
+++ b/fs/btrfs/xattr.c
@@ -316,6 +316,15 @@ ssize_t btrfs_getxattr(struct dentry *dentry, const char *name,
int btrfs_setxattr(struct dentry *dentry, const char *name, const void *value,
size_t size, int flags)
{
+ struct btrfs_root *root = BTRFS_I(dentry->d_inode)->root;
+
+ /*
+ * The permission on security.* and system.* is not checked
+ * in permission().
+ */
+ if (root->readonly)
+ return -EROFS;
+
/*
* If this is a request for a synthetic attribute in the system.*
* namespace use the generic infrastructure to resolve a handler
@@ -336,6 +345,15 @@ int btrfs_setxattr(struct dentry *dentry, const char *name, const void *value,
int btrfs_removexattr(struct dentry *dentry, const char *name)
{
+ struct btrfs_root *root = BTRFS_I(dentry->d_inode)->root;
+
+ /*
+ * The permission on security.* and system.* is not checked
+ * in permission().
+ */
+ if (root->readonly)
+ return -EROFS;
+
/*
* If this is a request for a synthetic attribute in the system.*
* namespace use the generic infrastructure to resolve a handler
--
1.6.3
--
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