[RFC PATCH v2] fuse: add new function to invalidate cache for all inodes

[RFC PATCH v2] fuse: add new function to invalidate cache for all inodes

[Luis Henriques]

Currently userspace is able to notify the kernel to invalidate the cache for
an inode.  This means that, if all the inodes in a filesystem need to be
invalidated, then userspace needs to iterate through all of them and do this
kernel notification separately.

This patch adds a new option that allows userspace to invalidate all the
inodes with a single notification operation.  In addition to invalidate all
the inodes, it also shrinks the sb dcache.

Signed-off-by: Luis Henriques <luis@igalia.com>
---
Hi!

As suggested by Bernd, this patch v2 simply adds an helper function that
will make it easier to replace most of it's code by a call to function
super_iter_inodes() when Dave Chinner's patch[1] eventually gets merged.

[1] https://lore.kernel.org/r/20241002014017.3801899-3-david@fromorbit.com

 fs/fuse/inode.c           | 59 +++++++++++++++++++++++++++++++++++++++
 include/uapi/linux/fuse.h |  3 ++
 2 files changed, 62 insertions(+)

diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index e9db2cb8c150..be51b53006d8 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -547,6 +547,62 @@ struct inode *fuse_ilookup(struct fuse_conn *fc, u64 nodeid,
 	return NULL;
 }
 
+static void inval_single_inode(struct inode *inode, struct fuse_conn *fc)
+{
+	struct fuse_inode *fi;
+
+	fi = get_fuse_inode(inode);
+	spin_lock(&fi->lock);
+	fi->attr_version = atomic64_inc_return(&fc->attr_version);
+	spin_unlock(&fi->lock);
+	fuse_invalidate_attr(inode);
+	forget_all_cached_acls(inode);
+}
+
+static int fuse_reverse_inval_all(struct fuse_conn *fc)
+{
+	struct fuse_mount *fm;
+	struct super_block *sb;
+	struct inode *inode, *old_inode = NULL;
+
+	inode = fuse_ilookup(fc, FUSE_ROOT_ID, NULL);
+	if (!inode)
+		return -ENOENT;
+
+	fm = get_fuse_mount(inode);
+	iput(inode);
+	if (!fm)
+		return -ENOENT;
+	sb = fm->sb;
+
+	spin_lock(&sb->s_inode_list_lock);
+	list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
+		spin_lock(&inode->i_lock);
+		if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
+		    !atomic_read(&inode->i_count)) {
+			spin_unlock(&inode->i_lock);
+			continue;
+		}
+
+		__iget(inode);
+		spin_unlock(&inode->i_lock);
+		spin_unlock(&sb->s_inode_list_lock);
+		iput(old_inode);
+
+		inval_single_inode(inode, fc);
+
+		old_inode = inode;
+		cond_resched();
+		spin_lock(&sb->s_inode_list_lock);
+	}
+	spin_unlock(&sb->s_inode_list_lock);
+	iput(old_inode);
+
+	shrink_dcache_sb(sb);
+
+	return 0;
+}
+
 int fuse_reverse_inval_inode(struct fuse_conn *fc, u64 nodeid,
 			     loff_t offset, loff_t len)
 {
@@ -555,6 +611,9 @@ int fuse_reverse_inval_inode(struct fuse_conn *fc, u64 nodeid,
 	pgoff_t pg_start;
 	pgoff_t pg_end;
 
+	if (nodeid == FUSE_INVAL_ALL_INODES)
+		return fuse_reverse_inval_all(fc);
+
 	inode = fuse_ilookup(fc, nodeid, NULL);
 	if (!inode)
 		return -ENOENT;
diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h
index 5e0eb41d967e..e5852b63f99f 100644
--- a/include/uapi/linux/fuse.h
+++ b/include/uapi/linux/fuse.h
@@ -669,6 +669,9 @@ enum fuse_notify_code {
 	FUSE_NOTIFY_CODE_MAX,
 };
 
+/* The nodeid to request to invalidate all inodes */
+#define FUSE_INVAL_ALL_INODES 0
+
 /* The read buffer is required to be at least 8k, but may be much larger */
 #define FUSE_MIN_READ_BUFFER 8192
 

Re: [RFC PATCH v2] fuse: add new function to invalidate cache for all inodes

[Bernd Schubert]

On 2/10/25 10:48, Luis Henriques wrote:
> Currently userspace is able to notify the kernel to invalidate the cache for
> an inode.  This means that, if all the inodes in a filesystem need to be
> invalidated, then userspace needs to iterate through all of them and do this
> kernel notification separately.
> 
> This patch adds a new option that allows userspace to invalidate all the
> inodes with a single notification operation.  In addition to invalidate all
> the inodes, it also shrinks the sb dcache.
> 
> Signed-off-by: Luis Henriques <luis@igalia.com>
> ---
> Hi!
> 
> As suggested by Bernd, this patch v2 simply adds an helper function that
> will make it easier to replace most of it's code by a call to function
> super_iter_inodes() when Dave Chinner's patch[1] eventually gets merged.
> 
> [1] https://lore.kernel.org/r/20241002014017.3801899-3-david@fromorbit.com
> 
>  fs/fuse/inode.c           | 59 +++++++++++++++++++++++++++++++++++++++
>  include/uapi/linux/fuse.h |  3 ++
>  2 files changed, 62 insertions(+)
> 
> diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
> index e9db2cb8c150..be51b53006d8 100644
> --- a/fs/fuse/inode.c
> +++ b/fs/fuse/inode.c
> @@ -547,6 +547,62 @@ struct inode *fuse_ilookup(struct fuse_conn *fc, u64 nodeid,
>  	return NULL;
>  }
>  
> +static void inval_single_inode(struct inode *inode, struct fuse_conn *fc)
> +{
> +	struct fuse_inode *fi;
> +
> +	fi = get_fuse_inode(inode);
> +	spin_lock(&fi->lock);
> +	fi->attr_version = atomic64_inc_return(&fc->attr_version);
> +	spin_unlock(&fi->lock);
> +	fuse_invalidate_attr(inode);
> +	forget_all_cached_acls(inode);


Thank you, much easier to read.

Could fuse_reverse_inval_inode() call into this? What are the semantics 
for  invalidate_inode_pages2_range() in this case? Totally invalidate?
No page cache invalidation at all as right now? If so, why?



Thanks,
Bernd

Re: [RFC PATCH v2] fuse: add new function to invalidate cache for all inodes

[Luis Henriques]

[re-sending -- for some reason I did a simple 'reply', not a 'reply-all'.]

On Mon, Feb 10 2025, Bernd Schubert wrote:

> On 2/10/25 10:48, Luis Henriques wrote:
>> Currently userspace is able to notify the kernel to invalidate the cache for
>> an inode.  This means that, if all the inodes in a filesystem need to be
>> invalidated, then userspace needs to iterate through all of them and do this
>> kernel notification separately.
>> 
>> This patch adds a new option that allows userspace to invalidate all the
>> inodes with a single notification operation.  In addition to invalidate all
>> the inodes, it also shrinks the sb dcache.
>> 
>> Signed-off-by: Luis Henriques <luis@igalia.com>
>> ---
>> Hi!
>> 
>> As suggested by Bernd, this patch v2 simply adds an helper function that
>> will make it easier to replace most of it's code by a call to function
>> super_iter_inodes() when Dave Chinner's patch[1] eventually gets merged.
>> 
>> [1] https://lore.kernel.org/r/20241002014017.3801899-3-david@fromorbit.com
>> 
>>  fs/fuse/inode.c           | 59 +++++++++++++++++++++++++++++++++++++++
>>  include/uapi/linux/fuse.h |  3 ++
>>  2 files changed, 62 insertions(+)
>> 
>> diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
>> index e9db2cb8c150..be51b53006d8 100644
>> --- a/fs/fuse/inode.c
>> +++ b/fs/fuse/inode.c
>> @@ -547,6 +547,62 @@ struct inode *fuse_ilookup(struct fuse_conn *fc, u64 nodeid,
>>  	return NULL;
>>  }
>>  
>> +static void inval_single_inode(struct inode *inode, struct fuse_conn *fc)
>> +{
>> +	struct fuse_inode *fi;
>> +
>> +	fi = get_fuse_inode(inode);
>> +	spin_lock(&fi->lock);
>> +	fi->attr_version = atomic64_inc_return(&fc->attr_version);
>> +	spin_unlock(&fi->lock);
>> +	fuse_invalidate_attr(inode);
>> +	forget_all_cached_acls(inode);
>
>
> Thank you, much easier to read.
>
> Could fuse_reverse_inval_inode() call into this?

Yep, it could indeed.  I'll do that in the next iteration, thanks!

> What are the semantics 
> for  invalidate_inode_pages2_range() in this case? Totally invalidate?
> No page cache invalidation at all as right now? If so, why?

So, if I change fuse_reverse_inval_inode() to use this help, it will still
need to keep the call to invalidate_inode_pages2_range().  But in the new
function fuse_reverse_inval_all(), I'm not doing it explicitly.  Instead,
that function calls into shrink_dcache_sb().  I *think* that by doing so
the invalidation will eventually happen.  Or am I wrong assuming that?

Cheers,
-- 
Luís

Re: [RFC PATCH v2] fuse: add new function to invalidate cache for all inodes

[Bernd Schubert]

On 2/10/25 11:48, Luis Henriques wrote:
> [re-sending -- for some reason I did a simple 'reply', not a 'reply-all'.]
> 
> On Mon, Feb 10 2025, Bernd Schubert wrote:
> 
>> On 2/10/25 10:48, Luis Henriques wrote:
>>> Currently userspace is able to notify the kernel to invalidate the cache for
>>> an inode.  This means that, if all the inodes in a filesystem need to be
>>> invalidated, then userspace needs to iterate through all of them and do this
>>> kernel notification separately.
>>>
>>> This patch adds a new option that allows userspace to invalidate all the
>>> inodes with a single notification operation.  In addition to invalidate all
>>> the inodes, it also shrinks the sb dcache.
>>>
>>> Signed-off-by: Luis Henriques <luis@igalia.com>
>>> ---
>>> Hi!
>>>
>>> As suggested by Bernd, this patch v2 simply adds an helper function that
>>> will make it easier to replace most of it's code by a call to function
>>> super_iter_inodes() when Dave Chinner's patch[1] eventually gets merged.
>>>
>>> [1] https://lore.kernel.org/r/20241002014017.3801899-3-david@fromorbit.com
>>>
>>>  fs/fuse/inode.c           | 59 +++++++++++++++++++++++++++++++++++++++
>>>  include/uapi/linux/fuse.h |  3 ++
>>>  2 files changed, 62 insertions(+)
>>>
>>> diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
>>> index e9db2cb8c150..be51b53006d8 100644
>>> --- a/fs/fuse/inode.c
>>> +++ b/fs/fuse/inode.c
>>> @@ -547,6 +547,62 @@ struct inode *fuse_ilookup(struct fuse_conn *fc, u64 nodeid,
>>>  	return NULL;
>>>  }
>>>  
>>> +static void inval_single_inode(struct inode *inode, struct fuse_conn *fc)
>>> +{
>>> +	struct fuse_inode *fi;
>>> +
>>> +	fi = get_fuse_inode(inode);
>>> +	spin_lock(&fi->lock);
>>> +	fi->attr_version = atomic64_inc_return(&fc->attr_version);
>>> +	spin_unlock(&fi->lock);
>>> +	fuse_invalidate_attr(inode);
>>> +	forget_all_cached_acls(inode);
>>
>>
>> Thank you, much easier to read.
>>
>> Could fuse_reverse_inval_inode() call into this?
> 
> Yep, it could indeed.  I'll do that in the next iteration, thanks!
> 
>> What are the semantics 
>> for  invalidate_inode_pages2_range() in this case? Totally invalidate?
>> No page cache invalidation at all as right now? If so, why?
> 
> So, if I change fuse_reverse_inval_inode() to use this help, it will still
> need to keep the call to invalidate_inode_pages2_range().  But in the new
> function fuse_reverse_inval_all(), I'm not doing it explicitly.  Instead,
> that function calls into shrink_dcache_sb().  I *think* that by doing so
> the invalidation will eventually happen.  Or am I wrong assuming that?

I think it will drop it, if the dentry cache is the last user/reference
of the inode. My issue is that it changes semantics a bit - without
FUSE_INVAL_ALL_INODES the page cache is invalidated based on the given
offset. Obviously we cannot give the offset for all inodes, but we
at least document the different semantics in a comment above
FUSE_INVAL_ALL_INODES? Sorry, should have asked earlier for it, just
busy with multiple things in parallel...


Thanks,
Bernd

Re: [RFC PATCH v2] fuse: add new function to invalidate cache for all inodes

[Luis Henriques]

On Mon, Feb 10 2025, Bernd Schubert wrote:

> On 2/10/25 11:48, Luis Henriques wrote:
>> [re-sending -- for some reason I did a simple 'reply', not a 'reply-all'.]
>> 
>> On Mon, Feb 10 2025, Bernd Schubert wrote:
>> 
>>> On 2/10/25 10:48, Luis Henriques wrote:
>>>> Currently userspace is able to notify the kernel to invalidate the cache for
>>>> an inode.  This means that, if all the inodes in a filesystem need to be
>>>> invalidated, then userspace needs to iterate through all of them and do this
>>>> kernel notification separately.
>>>>
>>>> This patch adds a new option that allows userspace to invalidate all the
>>>> inodes with a single notification operation.  In addition to invalidate all
>>>> the inodes, it also shrinks the sb dcache.
>>>>
>>>> Signed-off-by: Luis Henriques <luis@igalia.com>
>>>> ---
>>>> Hi!
>>>>
>>>> As suggested by Bernd, this patch v2 simply adds an helper function that
>>>> will make it easier to replace most of it's code by a call to function
>>>> super_iter_inodes() when Dave Chinner's patch[1] eventually gets merged.
>>>>
>>>> [1] https://lore.kernel.org/r/20241002014017.3801899-3-david@fromorbit.com
>>>>
>>>>  fs/fuse/inode.c           | 59 +++++++++++++++++++++++++++++++++++++++
>>>>  include/uapi/linux/fuse.h |  3 ++
>>>>  2 files changed, 62 insertions(+)
>>>>
>>>> diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
>>>> index e9db2cb8c150..be51b53006d8 100644
>>>> --- a/fs/fuse/inode.c
>>>> +++ b/fs/fuse/inode.c
>>>> @@ -547,6 +547,62 @@ struct inode *fuse_ilookup(struct fuse_conn *fc, u64 nodeid,
>>>>  	return NULL;
>>>>  }
>>>>  
>>>> +static void inval_single_inode(struct inode *inode, struct fuse_conn *fc)
>>>> +{
>>>> +	struct fuse_inode *fi;
>>>> +
>>>> +	fi = get_fuse_inode(inode);
>>>> +	spin_lock(&fi->lock);
>>>> +	fi->attr_version = atomic64_inc_return(&fc->attr_version);
>>>> +	spin_unlock(&fi->lock);
>>>> +	fuse_invalidate_attr(inode);
>>>> +	forget_all_cached_acls(inode);
>>>
>>>
>>> Thank you, much easier to read.
>>>
>>> Could fuse_reverse_inval_inode() call into this?
>> 
>> Yep, it could indeed.  I'll do that in the next iteration, thanks!
>> 
>>> What are the semantics 
>>> for  invalidate_inode_pages2_range() in this case? Totally invalidate?
>>> No page cache invalidation at all as right now? If so, why?
>> 
>> So, if I change fuse_reverse_inval_inode() to use this help, it will still
>> need to keep the call to invalidate_inode_pages2_range().  But in the new
>> function fuse_reverse_inval_all(), I'm not doing it explicitly.  Instead,
>> that function calls into shrink_dcache_sb().  I *think* that by doing so
>> the invalidation will eventually happen.  Or am I wrong assuming that?
>
> I think it will drop it, if the dentry cache is the last user/reference
> of the inode. My issue is that it changes semantics a bit - without
> FUSE_INVAL_ALL_INODES the page cache is invalidated based on the given
> offset. Obviously we cannot give the offset for all inodes, but we
> at least document the different semantics in a comment above
> FUSE_INVAL_ALL_INODES? Sorry, should have asked earlier for it, just
> busy with multiple things in parallel...

Yep, that makes sense.  In fact, my initial approach was to add a
completely different API with a FUSE_NOTIFY_INVAL_INODE_ALL operation.
But then I realized that I could simply hijack FUSE_NOTIFY_INVAL_INODE.
This would make things a lot easier, specially in the userspace side --
libfuse could even be used without *any* change at all.  (Obviously, I
expect to send a PR with the new flag and some documentation once this
patch is acceptable.)

Anyway, I'll also add some comments to this patch.  Thanks for your
feedback, Bernd.

Cheers,
-- 
Luís