2023-04-22 00:04:31

by Gabriel Krisman Bertazi

Subject: [PATCH v2 1/7] fs: Expose name under lookup to d_revalidate hook

From: Gabriel Krisman Bertazi <[email protected]>

Negative dentries support on case-insensitive ext4/f2fs will require
access to the name under lookup to ensure it matches the dentry. This
adds an optional new flavor of cached dentry revalidation hook to expose
this extra parameter.

I'm fine with extending d_revalidate instead of adding a new hook, if
it is considered cleaner and the approach is accepted. I wrote a new
hook to simplify reviewing.

Reviewed-by: Theodore Ts'o <[email protected]>
Signed-off-by: Gabriel Krisman Bertazi <[email protected]>
---
fs/dcache.c | 2 +-
fs/namei.c | 23 ++++++++++++++---------
include/linux/dcache.h | 1 +
3 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index 52e6d5fdab6b..98521862e58a 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1928,7 +1928,7 @@ void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
dentry->d_flags |= DCACHE_OP_HASH;
if (op->d_compare)
dentry->d_flags |= DCACHE_OP_COMPARE;
- if (op->d_revalidate)
+ if (op->d_revalidate || op->d_revalidate_name)
dentry->d_flags |= DCACHE_OP_REVALIDATE;
if (op->d_weak_revalidate)
dentry->d_flags |= DCACHE_OP_WEAK_REVALIDATE;
diff --git a/fs/namei.c b/fs/namei.c
index edfedfbccaef..c1557b69c45e 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -851,11 +851,16 @@ static bool try_to_unlazy_next(struct nameidata *nd, struct dentry *dentry)
return false;
}

-static inline int d_revalidate(struct dentry *dentry, unsigned int flags)
+static inline int d_revalidate(struct dentry *dentry,
+ const struct qstr *name,
+ unsigned int flags)
{
- if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE))
+
+ if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) {
+ if (dentry->d_op->d_revalidate_name)
+ return dentry->d_op->d_revalidate_name(dentry, name, flags);
return dentry->d_op->d_revalidate(dentry, flags);
- else
+ } else
return 1;
}

@@ -1563,7 +1568,7 @@ static struct dentry *lookup_dcache(const struct qstr *name,
{
struct dentry *dentry = d_lookup(dir, name);
if (dentry) {
- int error = d_revalidate(dentry, flags);
+ int error = d_revalidate(dentry, name, flags);
if (unlikely(error <= 0)) {
if (!error)
d_invalidate(dentry);
@@ -1632,19 +1637,19 @@ static struct dentry *lookup_fast(struct nameidata *nd)
if (read_seqcount_retry(&parent->d_seq, nd->seq))
return ERR_PTR(-ECHILD);

- status = d_revalidate(dentry, nd->flags);
+ status = d_revalidate(dentry, &nd->last, nd->flags);
if (likely(status > 0))
return dentry;
if (!try_to_unlazy_next(nd, dentry))
return ERR_PTR(-ECHILD);
if (status == -ECHILD)
/* we'd been told to redo it in non-rcu mode */
- status = d_revalidate(dentry, nd->flags);
+ status = d_revalidate(dentry, &nd->last, nd->flags);
} else {
dentry = __d_lookup(parent, &nd->last);
if (unlikely(!dentry))
return NULL;
- status = d_revalidate(dentry, nd->flags);
+ status = d_revalidate(dentry, &nd->last, nd->flags);
}
if (unlikely(status <= 0)) {
if (!status)
@@ -1672,7 +1677,7 @@ static struct dentry *__lookup_slow(const struct qstr *name,
if (IS_ERR(dentry))
return dentry;
if (unlikely(!d_in_lookup(dentry))) {
- int error = d_revalidate(dentry, flags);
+ int error = d_revalidate(dentry, name, flags);
if (unlikely(error <= 0)) {
if (!error) {
d_invalidate(dentry);
@@ -3345,7 +3350,7 @@ static struct dentry *lookup_open(struct nameidata *nd, struct file *file,
if (d_in_lookup(dentry))
break;

- error = d_revalidate(dentry, nd->flags);
+ error = d_revalidate(dentry, &nd->last, nd->flags);
if (likely(error > 0))
break;
if (error)
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 6b351e009f59..b6188f2e8950 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -127,6 +127,7 @@ enum dentry_d_lock_class

struct dentry_operations {
int (*d_revalidate)(struct dentry *, unsigned int);
+ int (*d_revalidate_name)(struct dentry *, const struct qstr *, unsigned int);
int (*d_weak_revalidate)(struct dentry *, unsigned int);
int (*d_hash)(const struct dentry *, struct qstr *);
int (*d_compare)(const struct dentry *,
--
2.40.0

2023-07-14 04:54:41

by Eric Biggers

Subject: Re: [PATCH v2 1/7] fs: Expose name under lookup to d_revalidate hook

Hi Gabriel,

On Fri, Apr 21, 2023 at 08:03:04PM -0400, Gabriel Krisman Bertazi wrote:
> From: Gabriel Krisman Bertazi <[email protected]>
>
> Negative dentries support on case-insensitive ext4/f2fs will require
> access to the name under lookup to ensure it matches the dentry. This
> adds an optional new flavor of cached dentry revalidation hook to expose
> this extra parameter.
>
> I'm fine with extending d_revalidate instead of adding a new hook, if
> it is considered cleaner and the approach is accepted. I wrote a new
> hook to simplify reviewing.
>
> Reviewed-by: Theodore Ts'o <[email protected]>
> Signed-off-by: Gabriel Krisman Bertazi <[email protected]>
> ---
> fs/dcache.c | 2 +-
> fs/namei.c | 23 ++++++++++++++---------
> include/linux/dcache.h | 1 +
> 3 files changed, 16 insertions(+), 10 deletions(-)

Documentation/filesystems/vfs.rst and Documentation/filesystems/locking.rst need
to be updated to document d_revalidate_name.

- Eric