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Commit dc3d3b81 authored by Ryusuke Konishi's avatar Ryusuke Konishi
Browse files

nilfs2: deny write access to inodes in snapshots 



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: default avatarRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
parent fd522029

fs/nilfs2/inode.c

+11 −0
Original line number Diff line number Diff line
@@ -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)

{

fs/nilfs2/namei.c

+1 −0
Original line number Diff line number Diff line
@@ -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 = {

fs/nilfs2/nilfs.h

+1 −3
Original line number Diff line number Diff line
@@ -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 *);