Re: [PATCH v2 2/4] fuse: simplify logic in fuse_notify_store() and fuse_retrieve()

["Darrick J. Wong" <djwong@kernel.org>]

On Tue, Jan 20, 2026 at 02:44:47PM -0800, Joanne Koong wrote:
> Simplify the folio parsing logic in fuse_notify_store() and
> fuse_retrieve().
> 
> In particular, calculate the index by tracking pos, which allows us to
> remove calculating nr_pages, and use "pos" in place of outarg's offset
> field.
> 
> Suggested-by: Jingbo Xu <jefflexu@linux.alibaba.com>
> Signed-off-by: Joanne Koong <joannelkoong@gmail.com>

Looks fine to me,
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

--D

> ---
>  fs/fuse/dev.c | 42 +++++++++++++++++-------------------------
>  1 file changed, 17 insertions(+), 25 deletions(-)
> 
> diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
> index 7558ff337413..9cbd5b64d9c9 100644
> --- a/fs/fuse/dev.c
> +++ b/fs/fuse/dev.c
> @@ -1765,10 +1765,9 @@ static int fuse_notify_store(struct fuse_conn *fc, unsigned int size,
>  	struct address_space *mapping;
>  	u64 nodeid;
>  	int err;
> -	pgoff_t index;
> -	unsigned int offset;
>  	unsigned int num;
>  	loff_t file_size;
> +	loff_t pos;
>  	loff_t end;
>  
>  	if (size < sizeof(outarg))
> @@ -1785,7 +1784,8 @@ static int fuse_notify_store(struct fuse_conn *fc, unsigned int size,
>  		return -EINVAL;
>  
>  	nodeid = outarg.nodeid;
> -	num = min(outarg.size, MAX_LFS_FILESIZE - outarg.offset);
> +	pos = outarg.offset;
> +	num = min(outarg.size, MAX_LFS_FILESIZE - pos);
>  
>  	down_read(&fc->killsb);
>  
> @@ -1795,10 +1795,8 @@ static int fuse_notify_store(struct fuse_conn *fc, unsigned int size,
>  		goto out_up_killsb;
>  
>  	mapping = inode->i_mapping;
> -	index = outarg.offset >> PAGE_SHIFT;
> -	offset = outarg.offset & ~PAGE_MASK;
>  	file_size = i_size_read(inode);
> -	end = outarg.offset + num;
> +	end = pos + num;
>  	if (end > file_size) {
>  		file_size = end;
>  		fuse_write_update_attr(inode, file_size, num);
> @@ -1808,19 +1806,18 @@ static int fuse_notify_store(struct fuse_conn *fc, unsigned int size,
>  		struct folio *folio;
>  		unsigned int folio_offset;
>  		unsigned int nr_bytes;
> -		unsigned int nr_pages;
> +		pgoff_t index = pos >> PAGE_SHIFT;
>  
>  		folio = filemap_grab_folio(mapping, index);
>  		err = PTR_ERR(folio);
>  		if (IS_ERR(folio))
>  			goto out_iput;
>  
> -		folio_offset = ((index - folio->index) << PAGE_SHIFT) + offset;
> -		nr_bytes = min_t(unsigned, num, folio_size(folio) - folio_offset);
> -		nr_pages = (offset + nr_bytes + PAGE_SIZE - 1) >> PAGE_SHIFT;
> +		folio_offset = offset_in_folio(folio, pos);
> +		nr_bytes = min(num, folio_size(folio) - folio_offset);
>  
>  		err = fuse_copy_folio(cs, &folio, folio_offset, nr_bytes, 0);
> -		if (!folio_test_uptodate(folio) && !err && offset == 0 &&
> +		if (!folio_test_uptodate(folio) && !err && folio_offset == 0 &&
>  		    (nr_bytes == folio_size(folio) || file_size == end)) {
>  			folio_zero_segment(folio, nr_bytes, folio_size(folio));
>  			folio_mark_uptodate(folio);
> @@ -1831,9 +1828,8 @@ static int fuse_notify_store(struct fuse_conn *fc, unsigned int size,
>  		if (err)
>  			goto out_iput;
>  
> +		pos += nr_bytes;
>  		num -= nr_bytes;
> -		offset = 0;
> -		index += nr_pages;
>  	}
>  
>  	err = 0;
> @@ -1865,7 +1861,6 @@ static int fuse_retrieve(struct fuse_mount *fm, struct inode *inode,
>  {
>  	int err;
>  	struct address_space *mapping = inode->i_mapping;
> -	pgoff_t index;
>  	loff_t file_size;
>  	unsigned int num;
>  	unsigned int offset;
> @@ -1876,15 +1871,16 @@ static int fuse_retrieve(struct fuse_mount *fm, struct inode *inode,
>  	size_t args_size = sizeof(*ra);
>  	struct fuse_args_pages *ap;
>  	struct fuse_args *args;
> +	loff_t pos = outarg->offset;
>  
> -	offset = outarg->offset & ~PAGE_MASK;
> +	offset = offset_in_page(pos);
>  	file_size = i_size_read(inode);
>  
>  	num = min(outarg->size, fc->max_write);
> -	if (outarg->offset > file_size)
> +	if (pos > file_size)
>  		num = 0;
> -	else if (num > file_size - outarg->offset)
> -		num = file_size - outarg->offset;
> +	else if (num > file_size - pos)
> +		num = file_size - pos;
>  
>  	num_pages = (num + offset + PAGE_SIZE - 1) >> PAGE_SHIFT;
>  	num_pages = min(num_pages, fc->max_pages);
> @@ -1907,31 +1903,27 @@ static int fuse_retrieve(struct fuse_mount *fm, struct inode *inode,
>  	args->in_pages = true;
>  	args->end = fuse_retrieve_end;
>  
> -	index = outarg->offset >> PAGE_SHIFT;
> -
>  	while (num && ap->num_folios < num_pages) {
>  		struct folio *folio;
>  		unsigned int folio_offset;
>  		unsigned int nr_bytes;
> -		unsigned int nr_pages;
> +		pgoff_t index = pos >> PAGE_SHIFT;
>  
>  		folio = filemap_get_folio(mapping, index);
>  		if (IS_ERR(folio))
>  			break;
>  
> -		folio_offset = ((index - folio->index) << PAGE_SHIFT) + offset;
> +		folio_offset = offset_in_folio(folio, pos);
>  		nr_bytes = min(folio_size(folio) - folio_offset, num);
> -		nr_pages = (offset + nr_bytes + PAGE_SIZE - 1) >> PAGE_SHIFT;
>  
>  		ap->folios[ap->num_folios] = folio;
>  		ap->descs[ap->num_folios].offset = folio_offset;
>  		ap->descs[ap->num_folios].length = nr_bytes;
>  		ap->num_folios++;
>  
> -		offset = 0;
> +		pos += nr_bytes;
>  		num -= nr_bytes;
>  		total_len += nr_bytes;
> -		index += nr_pages;
>  	}
>  	ra->inarg.offset = outarg->offset;
>  	ra->inarg.size = total_len;
> -- 
> 2.47.3
> 
>