On Tue, May 12, 2020 at 10:50:31AM +0300, Amir Goldstein wrote:
> This helper should be in vfs code, not duplicating vfs code
> and please don't duplicate code in vfs either.
>
> I think you can use a lookup flag (LOOKUP_POSITIVE_CACHE???)
> to describe the desired behavior and implement it inside
> lookup_slow(). Document the semantics as well as explain
> in the context of the helper the cases where modules might
> find this useful (because they have higher level caches).
>
> Besides the fact that this helper really needs review by Al
> and that duplicating subtle code is wrong in so many levels,
> I suppose the functionality could prove useful to other subsystems
> as well.
Something like this (untested). Needs splitup and changelogs.
Thanks,
Miklos
---
diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index c31f362fa098..e52a3b35ebac 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -752,7 +752,7 @@ cifs_get_root(struct smb_vol *vol, struct super_block *sb)
while (*s && *s != sep)
s++;
- child = lookup_positive_unlocked(p, dentry, s - p);
+ child = lookup_positive_unlocked(p, dentry, s - p, 0);
dput(dentry);
dentry = child;
} while (!IS_ERR(dentry));
diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index b7f2e971ecbc..df4f37a6a9ab 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -299,7 +299,7 @@ struct dentry *debugfs_lookup(const char *name, struct dentry *parent)
if (!parent)
parent = debugfs_mount->mnt_root;
- dentry = lookup_positive_unlocked(name, parent, strlen(name));
+ dentry = lookup_positive_unlocked(name, parent, strlen(name), 0);
if (IS_ERR(dentry))
return NULL;
return dentry;
diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
index e23752d9a79f..e39af6313ad9 100644
--- a/fs/ecryptfs/inode.c
+++ b/fs/ecryptfs/inode.c
@@ -407,7 +407,7 @@ static struct dentry *ecryptfs_lookup(struct inode *ecryptfs_dir_inode,
name = encrypted_and_encoded_name;
}
- lower_dentry = lookup_one_len_unlocked(name, lower_dir_dentry, len);
+ lower_dentry = lookup_one_len_unlocked(name, lower_dir_dentry, len, 0);
if (IS_ERR(lower_dentry)) {
ecryptfs_printk(KERN_DEBUG, "%s: lookup_one_len() returned "
"[%ld] on lower_dentry = [%s]\n", __func__,
diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
index 2dd55b172d57..a4276d14aebb 100644
--- a/fs/exportfs/expfs.c
+++ b/fs/exportfs/expfs.c
@@ -145,7 +145,7 @@ static struct dentry *reconnect_one(struct vfsmount *mnt,
if (err)
goto out_err;
dprintk("%s: found name: %s\n", __func__, nbuf);
- tmp = lookup_one_len_unlocked(nbuf, parent, strlen(nbuf));
+ tmp = lookup_one_len_unlocked(nbuf, parent, strlen(nbuf), 0);
if (IS_ERR(tmp)) {
dprintk("%s: lookup failed: %d\n", __func__, PTR_ERR(tmp));
err = PTR_ERR(tmp);
diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c
index 9dc7e7a64e10..92e7f264baa1 100644
--- a/fs/kernfs/mount.c
+++ b/fs/kernfs/mount.c
@@ -224,7 +224,7 @@ struct dentry *kernfs_node_dentry(struct kernfs_node *kn,
return ERR_PTR(-EINVAL);
}
dtmp = lookup_positive_unlocked(kntmp->name, dentry,
- strlen(kntmp->name));
+ strlen(kntmp->name), 0);
dput(dentry);
if (IS_ERR(dtmp))
return dtmp;
diff --git a/fs/namei.c b/fs/namei.c
index a320371899cf..e70b7a14bdcc 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1532,6 +1532,9 @@ static struct dentry *__lookup_slow(const struct qstr *name,
if (unlikely(old)) {
dput(dentry);
dentry = old;
+ } else if ((flags & LOOKUP_NO_NEGATIVE) &&
+ d_is_negative(dentry)) {
+ d_drop(dentry);
}
}
return dentry;
@@ -2562,7 +2565,8 @@ EXPORT_SYMBOL(lookup_one_len);
* i_mutex held, and will take the i_mutex itself if necessary.
*/
struct dentry *lookup_one_len_unlocked(const char *name,
- struct dentry *base, int len)
+ struct dentry *base, int len,
+ unsigned int flags)
{
struct qstr this;
int err;
@@ -2572,9 +2576,9 @@ struct dentry *lookup_one_len_unlocked(const char *name,
if (err)
return ERR_PTR(err);
- ret = lookup_dcache(&this, base, 0);
+ ret = lookup_dcache(&this, base, flags);
if (!ret)
- ret = lookup_slow(&this, base, 0);
+ ret = lookup_slow(&this, base, flags);
return ret;
}
EXPORT_SYMBOL(lookup_one_len_unlocked);
@@ -2588,9 +2592,10 @@ EXPORT_SYMBOL(lookup_one_len_unlocked);
* this one avoids such problems.
*/
struct dentry *lookup_positive_unlocked(const char *name,
- struct dentry *base, int len)
+ struct dentry *base, int len,
+ unsigned int flags)
{
- struct dentry *ret = lookup_one_len_unlocked(name, base, len);
+ struct dentry *ret = lookup_one_len_unlocked(name, base, len, flags);
if (!IS_ERR(ret) && d_flags_negative(smp_load_acquire(&ret->d_flags))) {
dput(ret);
ret = ERR_PTR(-ENOENT);
diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
index aae514d40b64..19628922969c 100644
--- a/fs/nfsd/nfs3xdr.c
+++ b/fs/nfsd/nfs3xdr.c
@@ -855,7 +855,7 @@ compose_entry_fh(struct nfsd3_readdirres *cd, struct svc_fh *fhp,
} else
dchild = dget(dparent);
} else
- dchild = lookup_positive_unlocked(name, dparent, namlen);
+ dchild = lookup_positive_unlocked(name, dparent, namlen, 0);
if (IS_ERR(dchild))
return rv;
if (d_mountpoint(dchild))
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 996ac01ee977..0c3c7928a319 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -3066,7 +3066,7 @@ nfsd4_encode_dirent_fattr(struct xdr_stream *xdr, struct nfsd4_readdir *cd,
__be32 nfserr;
int ignore_crossmnt = 0;
- dentry = lookup_positive_unlocked(name, cd->rd_fhp->fh_dentry, namlen);
+ dentry = lookup_positive_unlocked(name, cd->rd_fhp->fh_dentry, namlen, 0);
if (IS_ERR(dentry))
return nfserrno(PTR_ERR(dentry));
diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index 0db23baf98e7..193857487060 100644
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -200,7 +200,8 @@ static int ovl_lookup_single(struct dentry *base, struct ovl_lookup_data *d,
int err;
bool last_element = !post[0];
- this = lookup_positive_unlocked(name, base, namelen);
+ this = lookup_positive_unlocked(name, base, namelen,
+ LOOKUP_NO_NEGATIVE);
if (IS_ERR(this)) {
err = PTR_ERR(this);
this = NULL;
@@ -657,7 +658,7 @@ struct dentry *ovl_get_index_fh(struct ovl_fs *ofs, struct ovl_fh *fh)
if (err)
return ERR_PTR(err);
- index = lookup_positive_unlocked(name.name, ofs->indexdir, name.len);
+ index = lookup_positive_unlocked(name.name, ofs->indexdir, name.len, 0);
kfree(name.name);
if (IS_ERR(index)) {
if (PTR_ERR(index) == -ENOENT)
@@ -689,7 +690,7 @@ struct dentry *ovl_lookup_index(struct ovl_fs *ofs, struct dentry *upper,
if (err)
return ERR_PTR(err);
- index = lookup_positive_unlocked(name.name, ofs->indexdir, name.len);
+ index = lookup_positive_unlocked(name.name, ofs->indexdir, name.len, 0);
if (IS_ERR(index)) {
err = PTR_ERR(index);
if (err == -ENOENT) {
@@ -1137,7 +1138,7 @@ bool ovl_lower_positive(struct dentry *dentry)
struct dentry *lowerdir = poe->lowerstack[i].dentry;
this = lookup_positive_unlocked(name->name, lowerdir,
- name->len);
+ name->len, 0);
if (IS_ERR(this)) {
switch (PTR_ERR(this)) {
case -ENOENT:
diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index b6a4f692d345..f588839ebe2e 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -2488,7 +2488,7 @@ int dquot_quota_on_mount(struct super_block *sb, char *qf_name,
struct dentry *dentry;
int error;
- dentry = lookup_positive_unlocked(qf_name, sb->s_root, strlen(qf_name));
+ dentry = lookup_positive_unlocked(qf_name, sb->s_root, strlen(qf_name), 0);
if (IS_ERR(dentry))
return PTR_ERR(dentry);
diff --git a/include/linux/namei.h b/include/linux/namei.h
index a4bb992623c4..4896eeeeea46 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -49,6 +49,8 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT};
/* LOOKUP_* flags which do scope-related checks based on the dirfd. */
#define LOOKUP_IS_SCOPED (LOOKUP_BENEATH | LOOKUP_IN_ROOT)
+#define LOOKUP_NO_NEGATIVE 0x200000 /* Hint: don't cache negative */
+
extern int path_pts(struct path *path);
extern int user_path_at_empty(int, const char __user *, unsigned, struct path *, int *empty);
@@ -68,8 +70,8 @@ extern struct dentry *kern_path_locked(const char *, struct path *);
extern struct dentry *try_lookup_one_len(const char *, struct dentry *, int);
extern struct dentry *lookup_one_len(const char *, struct dentry *, int);
-extern struct dentry *lookup_one_len_unlocked(const char *, struct dentry *, int);
-extern struct dentry *lookup_positive_unlocked(const char *, struct dentry *, int);
+extern struct dentry *lookup_one_len_unlocked(const char *, struct dentry *, int, unsigned int);
+extern struct dentry *lookup_positive_unlocked(const char *, struct dentry *, int, unsigned int);
extern int follow_down_one(struct path *);
extern int follow_down(struct path *);
