[PATCH v3] fuse: fix premature writetrhough request for large folio

[PATCH v3] fuse: fix premature writetrhough request for large folio

[Jingbo Xu]

When large folio is enabled and the initial folio offset exceeds
PAGE_SIZE, e.g. the position resides in the second page of a large
folio, after the folio copying the offset (in the page) won't be updated
to 0 even though the expected range is successfully copied until the end
of the folio.  In this case fuse_fill_write_pages() exits prematurelly
before the request has reached the max_write/max_pages limit.

Fix this by eliminating page offset entirely and use folio offset
instead.

Fixes: d60a6015e1a2 ("fuse: support large folios for writethrough writes")
Reviewed-by: Horst Birthelmer <hbirthelmer@ddn.com>
Reviewed-by: Joanne Koong <joannelkoong@gmail.com>
Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
---
changes since v2:
- drop stable CC tag; add Reviewed-by tag by Joanne

v1: https://lore.kernel.org/all/20260114055615.17903-1-jefflexu@linux.alibaba.com/
v2: https://lore.kernel.org/all/20260114124514.62998-1-jefflexu@linux.alibaba.com/
---
 fs/fuse/file.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 625d236b881b..6aafb32338b6 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1272,7 +1272,6 @@ static ssize_t fuse_fill_write_pages(struct fuse_io_args *ia,
 {
 	struct fuse_args_pages *ap = &ia->ap;
 	struct fuse_conn *fc = get_fuse_conn(mapping->host);
-	unsigned offset = pos & (PAGE_SIZE - 1);
 	size_t count = 0;
 	unsigned int num;
 	int err = 0;
@@ -1299,7 +1298,7 @@ static ssize_t fuse_fill_write_pages(struct fuse_io_args *ia,
 		if (mapping_writably_mapped(mapping))
 			flush_dcache_folio(folio);
 
-		folio_offset = ((index - folio->index) << PAGE_SHIFT) + offset;
+		folio_offset = offset_in_folio(folio, pos);
 		bytes = min(folio_size(folio) - folio_offset, num);
 
 		tmp = copy_folio_from_iter_atomic(folio, folio_offset, bytes, ii);
@@ -1329,9 +1328,6 @@ static ssize_t fuse_fill_write_pages(struct fuse_io_args *ia,
 		count += tmp;
 		pos += tmp;
 		num -= tmp;
-		offset += tmp;
-		if (offset == folio_size(folio))
-			offset = 0;
 
 		/* If we copied full folio, mark it uptodate */
 		if (tmp == folio_size(folio))
@@ -1343,7 +1339,9 @@ static ssize_t fuse_fill_write_pages(struct fuse_io_args *ia,
 			ia->write.folio_locked = true;
 			break;
 		}
-		if (!fc->big_writes || offset != 0)
+		if (!fc->big_writes)
+			break;
+		if (folio_offset + tmp != folio_size(folio))
 			break;
 	}
 
-- 
2.19.1.6.gb485710b

Re: [PATCH v3] fuse: fix premature writetrhough request for large folio

[Jingbo Xu]

On 1/15/26 10:36 AM, Jingbo Xu wrote:
> When large folio is enabled and the initial folio offset exceeds
> PAGE_SIZE, e.g. the position resides in the second page of a large
> folio, after the folio copying the offset (in the page) won't be updated
> to 0 even though the expected range is successfully copied until the end
> of the folio.  In this case fuse_fill_write_pages() exits prematurelly
> before the request has reached the max_write/max_pages limit.
> 
> Fix this by eliminating page offset entirely and use folio offset
> instead.
> 
> Fixes: d60a6015e1a2 ("fuse: support large folios for writethrough writes")
> Reviewed-by: Horst Birthelmer <hbirthelmer@ddn.com>
> Reviewed-by: Joanne Koong <joannelkoong@gmail.com>
> Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
> ---
> changes since v2:
> - drop stable CC tag; add Reviewed-by tag by Joanne
> 
> v1: https://lore.kernel.org/all/20260114055615.17903-1-jefflexu@linux.alibaba.com/
> v2: https://lore.kernel.org/all/20260114124514.62998-1-jefflexu@linux.alibaba.com/

gentle ping...

> ---
>  fs/fuse/file.c | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index 625d236b881b..6aafb32338b6 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -1272,7 +1272,6 @@ static ssize_t fuse_fill_write_pages(struct fuse_io_args *ia,
>  {
>  	struct fuse_args_pages *ap = &ia->ap;
>  	struct fuse_conn *fc = get_fuse_conn(mapping->host);
> -	unsigned offset = pos & (PAGE_SIZE - 1);
>  	size_t count = 0;
>  	unsigned int num;
>  	int err = 0;
> @@ -1299,7 +1298,7 @@ static ssize_t fuse_fill_write_pages(struct fuse_io_args *ia,
>  		if (mapping_writably_mapped(mapping))
>  			flush_dcache_folio(folio);
>  
> -		folio_offset = ((index - folio->index) << PAGE_SHIFT) + offset;
> +		folio_offset = offset_in_folio(folio, pos);
>  		bytes = min(folio_size(folio) - folio_offset, num);
>  
>  		tmp = copy_folio_from_iter_atomic(folio, folio_offset, bytes, ii);
> @@ -1329,9 +1328,6 @@ static ssize_t fuse_fill_write_pages(struct fuse_io_args *ia,
>  		count += tmp;
>  		pos += tmp;
>  		num -= tmp;
> -		offset += tmp;
> -		if (offset == folio_size(folio))
> -			offset = 0;
>  
>  		/* If we copied full folio, mark it uptodate */
>  		if (tmp == folio_size(folio))
> @@ -1343,7 +1339,9 @@ static ssize_t fuse_fill_write_pages(struct fuse_io_args *ia,
>  			ia->write.folio_locked = true;
>  			break;
>  		}
> -		if (!fc->big_writes || offset != 0)
> +		if (!fc->big_writes)
> +			break;
> +		if (folio_offset + tmp != folio_size(folio))
>  			break;
>  	}
>  

-- 
Thanks,
Jingbo

Re: [PATCH v3] fuse: fix premature writetrhough request for large folio

[Miklos Szeredi]

On Thu, 15 Jan 2026 at 03:36, Jingbo Xu <jefflexu@linux.alibaba.com> wrote:
>
> When large folio is enabled and the initial folio offset exceeds
> PAGE_SIZE, e.g. the position resides in the second page of a large
> folio, after the folio copying the offset (in the page) won't be updated
> to 0 even though the expected range is successfully copied until the end
> of the folio.  In this case fuse_fill_write_pages() exits prematurelly
> before the request has reached the max_write/max_pages limit.
>
> Fix this by eliminating page offset entirely and use folio offset
> instead.
>
> Fixes: d60a6015e1a2 ("fuse: support large folios for writethrough writes")
> Reviewed-by: Horst Birthelmer <hbirthelmer@ddn.com>
> Reviewed-by: Joanne Koong <joannelkoong@gmail.com>
> Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>

Applied, thanks.

Miklos