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nilfs2: deny write access to inodes in snapshots

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Snapshots of nilfs are read-only.

After super block instances (sb) will be unified, nilfs will need to
check write access by a way other than implicit test with
IS_RDONLY(inode).  This is because IS_RDONLY() refers to MS_RDONLY bit
of inode->i_sb->s_flags and it will become inaccurate after the
unification of sb.

To prepare for the issue, this uses i_op->permission to deny write
access to inodes in snapshots.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
This commit is contained in:
Ryusuke Konishi 2010-08-15 23:33:57 +09:00
parent fd52202930
commit dc3d3b810a
3 changed files with 13 additions and 3 deletions
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11
fs/nilfs2/inode.c
View File

@ -764,6 +764,17 @@ out_err:
return err;
}
int nilfs_permission(struct inode *inode, int mask)
{
struct nilfs_root *root = NILFS_I(inode)->i_root;
if ((mask & MAY_WRITE) && root &&
root->cno != NILFS_CPTREE_CURRENT_CNO)
return -EROFS; /* snapshot is not writable */
return generic_permission(inode, mask, NULL);
}
int nilfs_load_inode_block(struct nilfs_sb_info *sbi, struct inode *inode,
struct buffer_head **pbh)
{

1
fs/nilfs2/namei.c
View File

@ -588,6 +588,7 @@ const struct inode_operations nilfs_symlink_inode_operations = {
.readlink = generic_readlink,
.follow_link = page_follow_link_light,
.put_link = page_put_link,
.permission = nilfs_permission,
};
const struct export_operations nilfs_export_ops = {

4
fs/nilfs2/nilfs.h
View File

@ -201,12 +201,9 @@ static inline struct inode *nilfs_dat_inode(const struct the_nilfs *nilfs)
*/
#ifdef CONFIG_NILFS_POSIX_ACL
#error "NILFS: not yet supported POSIX ACL"
extern int nilfs_permission(struct inode *, int, struct nameidata *);
extern int nilfs_acl_chmod(struct inode *);
extern int nilfs_init_acl(struct inode *, struct inode *);
#else
#define nilfs_permission NULL
static inline int nilfs_acl_chmod(struct inode *inode)
{
return 0;
@ -256,6 +253,7 @@ extern void nilfs_update_inode(struct inode *, struct buffer_head *);
extern void nilfs_truncate(struct inode *);
extern void nilfs_evict_inode(struct inode *);
extern int nilfs_setattr(struct dentry *, struct iattr *);
int nilfs_permission(struct inode *inode, int mask);
extern int nilfs_load_inode_block(struct nilfs_sb_info *, struct inode *,
struct buffer_head **);
extern int nilfs_inode_dirty(struct inode *);