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ovl: store real inode pointer in ->i_private

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To get from overlay inode to real inode we currently use 'struct
ovl_entry', which has lifetime connected to overlay dentry.  This is okay,
since each overlay dentry had a new overlay inode allocated.

Following patch will break that assumption, so need to leave out ovl_entry.
This patch stores the real inode directly in i_private, with the lowest bit
used to indicate whether the inode is upper or lower.

Lifetime rules remain, using ovl_inode_real() must only be done while
caller holds ref on overlay dentry (and hence on real dentry), or within
RCU protected regions.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
Miklos Szeredi
2016-07-29 12:05:24 +02:00
parent a999d7e161
commit 39b681f802
5 changed files with 40 additions and 37 deletions
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11
fs/overlayfs/inode.c
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@@ -117,15 +117,12 @@ static int ovl_getattr(struct vfsmount *mnt, struct dentry *dentry,
int ovl_permission(struct inode *inode, int mask)
{
struct ovl_entry *oe = inode->i_private;
bool is_upper;
struct dentry *realdentry = ovl_entry_real(oe, &is_upper);
struct inode *realinode;
struct inode *realinode = ovl_inode_real(inode, &is_upper);
const struct cred *old_cred;
int err;
/* Careful in RCU walk mode */
realinode = d_inode_rcu(realdentry);
if (!realinode) {
WARN_ON(!(mask & MAY_NOT_BLOCK));
return -ECHILD;
@@ -312,7 +309,7 @@ out:
struct posix_acl *ovl_get_acl(struct inode *inode, int type)
{
struct inode *realinode = ovl_inode_real(inode);
struct inode *realinode = ovl_inode_real(inode, NULL);
const struct cred *old_cred;
struct posix_acl *acl;
@@ -412,8 +409,7 @@ static const struct inode_operations ovl_symlink_inode_operations = {
.update_time = ovl_update_time,
};
struct inode *ovl_new_inode(struct super_block *sb, umode_t mode,
struct ovl_entry *oe)
struct inode *ovl_new_inode(struct super_block *sb, umode_t mode)
{
struct inode *inode;
@@ -424,7 +420,6 @@ struct inode *ovl_new_inode(struct super_block *sb, umode_t mode,
inode->i_ino = get_next_ino();
inode->i_mode = mode;
inode->i_flags |= S_NOCMTIME;
inode->i_private = oe;
mode &= S_IFMT;
switch (mode) {