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ovl: multi-layer lookup

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Look up dentry in all relevant layers.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
This commit is contained in:
Miklos Szeredi 2014-12-13 00:59:44 +01:00
parent 9d7459d834
commit 3d3c6b8939
1 changed files with 94 additions and 49 deletions
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143
fs/overlayfs/super.c
View file

@ -333,82 +333,127 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
unsigned int flags)
{
struct ovl_entry *oe;
struct dentry *upperdir;
struct path lowerdir;
struct dentry *upperdentry = NULL;
struct dentry *lowerdentry = NULL;
struct ovl_entry *poe = dentry->d_parent->d_fsdata;
struct path *stack = NULL;
struct dentry *upperdir, *upperdentry = NULL;
unsigned int ctr = 0;
struct inode *inode = NULL;
bool upperopaque = false;
struct dentry *this, *prev = NULL;
unsigned int i;
int err;
err = -ENOMEM;
oe = ovl_alloc_entry(1);
if (!oe)
goto out;
upperdir = ovl_dentry_upper(dentry->d_parent);
ovl_path_lower(dentry->d_parent, &lowerdir);
upperdir = ovl_upperdentry_dereference(poe);
if (upperdir) {
upperdentry = ovl_lookup_real(upperdir, &dentry->d_name);
err = PTR_ERR(upperdentry);
if (IS_ERR(upperdentry))
goto out_put_dir;
this = ovl_lookup_real(upperdir, &dentry->d_name);
err = PTR_ERR(this);
if (IS_ERR(this))
goto out;
if (lowerdir.dentry && upperdentry) {
if (ovl_is_whiteout(upperdentry)) {
dput(upperdentry);
upperdentry = NULL;
oe->opaque = true;
} else if (ovl_is_opaquedir(upperdentry)) {
oe->opaque = true;
/*
* If this is not the lowermost layer, check whiteout and opaque
* directory.
*/
if (poe->numlower && this) {
if (ovl_is_whiteout(this)) {
dput(this);
this = NULL;
upperopaque = true;
} else if (ovl_is_opaquedir(this)) {
upperopaque = true;
}
}
}
if (lowerdir.dentry && !oe->opaque) {
lowerdentry = ovl_lookup_real(lowerdir.dentry, &dentry->d_name);
err = PTR_ERR(lowerdentry);
if (IS_ERR(lowerdentry))
goto out_dput_upper;
upperdentry = prev = this;
}
if (lowerdentry && upperdentry &&
(!S_ISDIR(upperdentry->d_inode->i_mode) ||
!S_ISDIR(lowerdentry->d_inode->i_mode))) {
dput(lowerdentry);
lowerdentry = NULL;
oe->opaque = true;
if (!upperopaque && poe->numlower) {
err = -ENOMEM;
stack = kcalloc(poe->numlower, sizeof(struct path), GFP_KERNEL);
if (!stack)
goto out_put_upper;
}
if (lowerdentry || upperdentry) {
for (i = 0; !upperopaque && i < poe->numlower; i++) {
bool opaque = false;
struct path lowerpath = poe->lowerstack[i];
opaque = false;
this = ovl_lookup_real(lowerpath.dentry, &dentry->d_name);
err = PTR_ERR(this);
if (IS_ERR(this))
goto out_put;
if (!this)
continue;
/*
* If this is not the lowermost layer, check whiteout and opaque
* directory.
*/
if (i < poe->numlower - 1) {
if (ovl_is_whiteout(this)) {
dput(this);
break;
} else if (ovl_is_opaquedir(this)) {
opaque = true;
}
}
/*
* If this is a non-directory then stop here.
*
* FIXME: check for opaqueness maybe better done in remove code.
*/
if (!S_ISDIR(this->d_inode->i_mode)) {
opaque = true;
} else if (prev && (!S_ISDIR(prev->d_inode->i_mode) ||
!S_ISDIR(this->d_inode->i_mode))) {
if (prev == upperdentry)
upperopaque = true;
dput(this);
break;
}
stack[ctr].dentry = this;
stack[ctr].mnt = lowerpath.mnt;
ctr++;
prev = this;
if (opaque)
break;
}
oe = ovl_alloc_entry(ctr);
err = -ENOMEM;
if (!oe)
goto out_put;
if (upperdentry || ctr) {
struct dentry *realdentry;
realdentry = upperdentry ? upperdentry : lowerdentry;
realdentry = upperdentry ? upperdentry : stack[0].dentry;
err = -ENOMEM;
inode = ovl_new_inode(dentry->d_sb, realdentry->d_inode->i_mode,
oe);
if (!inode)
goto out_dput;
goto out_free_oe;
ovl_copyattr(realdentry->d_inode, inode);
}
oe->opaque = upperopaque;
oe->__upperdentry = upperdentry;
if (lowerdentry) {
oe->lowerstack[0].dentry = lowerdentry;
oe->lowerstack[0].mnt = lowerdir.mnt;
} else {
oe->numlower = 0;
}
memcpy(oe->lowerstack, stack, sizeof(struct path) * ctr);
kfree(stack);
dentry->d_fsdata = oe;
d_add(dentry, inode);
return NULL;
out_dput:
dput(lowerdentry);
out_dput_upper:
dput(upperdentry);
out_put_dir:
out_free_oe:
kfree(oe);
out_put:
for (i = 0; i < ctr; i++)
dput(stack[i].dentry);
kfree(stack);
out_put_upper:
dput(upperdentry);
out:
return ERR_PTR(err);
}