[PATCH] btrfs: compression: Adjust cb->compressed_folios allocation type

[PATCH] btrfs: compression: Adjust cb->compressed_folios allocation type

[Kees Cook]

In preparation for making the kmalloc family of allocators type aware,
we need to make sure that the returned type from the allocation matches
the type of the variable being assigned. (Before, the allocator would
always return "void *", which can be implicitly cast to any pointer type.)

The assigned type is "struct folio **" but the returned type will be
"struct page **". These are the same allocation size (pointer size), but
the types don't match. Adjust the allocation type to match the assignment.

Signed-off-by: Kees Cook <kees@kernel.org>
---
Cc: Chris Mason <clm@fb.com>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: David Sterba <dsterba@suse.com>
Cc: <linux-btrfs@vger.kernel.org>
---
 fs/btrfs/compression.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index e7f8ee5d48a4..7f11ef559be6 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -606,7 +606,7 @@ void btrfs_submit_compressed_read(struct btrfs_bio *bbio)
 	free_extent_map(em);
 
 	cb->nr_folios = DIV_ROUND_UP(compressed_len, PAGE_SIZE);
-	cb->compressed_folios = kcalloc(cb->nr_folios, sizeof(struct page *), GFP_NOFS);
+	cb->compressed_folios = kcalloc(cb->nr_folios, sizeof(struct folio *), GFP_NOFS);
 	if (!cb->compressed_folios) {
 		ret = BLK_STS_RESOURCE;
 		goto out_free_bio;
-- 
2.34.1

Re: [PATCH] btrfs: compression: Adjust cb->compressed_folios allocation type

[Qu Wenruo]

在 2025/4/26 15:53, Kees Cook 写道:
> In preparation for making the kmalloc family of allocators type aware,
> we need to make sure that the returned type from the allocation matches
> the type of the variable being assigned. (Before, the allocator would
> always return "void *", which can be implicitly cast to any pointer type.)
> 
> The assigned type is "struct folio **" but the returned type will be
> "struct page **". These are the same allocation size (pointer size), but
> the types don't match. Adjust the allocation type to match the assignment.
> 
> Signed-off-by: Kees Cook <kees@kernel.org>

Reviewed-by: Qu Wenruo <wqu@suse.com>

Thanks,
Qu

> ---
> Cc: Chris Mason <clm@fb.com>
> Cc: Josef Bacik <josef@toxicpanda.com>
> Cc: David Sterba <dsterba@suse.com>
> Cc: <linux-btrfs@vger.kernel.org>
> ---
>   fs/btrfs/compression.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
> index e7f8ee5d48a4..7f11ef559be6 100644
> --- a/fs/btrfs/compression.c
> +++ b/fs/btrfs/compression.c
> @@ -606,7 +606,7 @@ void btrfs_submit_compressed_read(struct btrfs_bio *bbio)
>   	free_extent_map(em);
>   
>   	cb->nr_folios = DIV_ROUND_UP(compressed_len, PAGE_SIZE);
> -	cb->compressed_folios = kcalloc(cb->nr_folios, sizeof(struct page *), GFP_NOFS);
> +	cb->compressed_folios = kcalloc(cb->nr_folios, sizeof(struct folio *), GFP_NOFS);
>   	if (!cb->compressed_folios) {
>   		ret = BLK_STS_RESOURCE;
>   		goto out_free_bio;

Re: [PATCH] btrfs: compression: Adjust cb->compressed_folios allocation type

[Gustavo A. R. Silva]

On 26/04/25 00:23, Kees Cook wrote:
> In preparation for making the kmalloc family of allocators type aware,
> we need to make sure that the returned type from the allocation matches
> the type of the variable being assigned. (Before, the allocator would
> always return "void *", which can be implicitly cast to any pointer type.)
> 
> The assigned type is "struct folio **" but the returned type will be
> "struct page **". These are the same allocation size (pointer size), but
> the types don't match. Adjust the allocation type to match the assignment.
> 
> Signed-off-by: Kees Cook <kees@kernel.org>
> ---
> Cc: Chris Mason <clm@fb.com>
> Cc: Josef Bacik <josef@toxicpanda.com>
> Cc: David Sterba <dsterba@suse.com>
> Cc: <linux-btrfs@vger.kernel.org>
> ---
>   fs/btrfs/compression.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
> index e7f8ee5d48a4..7f11ef559be6 100644
> --- a/fs/btrfs/compression.c
> +++ b/fs/btrfs/compression.c
> @@ -606,7 +606,7 @@ void btrfs_submit_compressed_read(struct btrfs_bio *bbio)
>   	free_extent_map(em);
>   
>   	cb->nr_folios = DIV_ROUND_UP(compressed_len, PAGE_SIZE);
> -	cb->compressed_folios = kcalloc(cb->nr_folios, sizeof(struct page *), GFP_NOFS);
> +	cb->compressed_folios = kcalloc(cb->nr_folios, sizeof(struct folio *), GFP_NOFS);

Why not `sizeof(*cb->compressed_folios)` as in other patches? :)

-Gustavo

Re: [PATCH] btrfs: compression: Adjust cb->compressed_folios allocation type

[David Sterba]

On Fri, Apr 25, 2025 at 11:23:29PM -0700, Kees Cook wrote:
> In preparation for making the kmalloc family of allocators type aware,
> we need to make sure that the returned type from the allocation matches
> the type of the variable being assigned. (Before, the allocator would
> always return "void *", which can be implicitly cast to any pointer type.)
> 
> The assigned type is "struct folio **" but the returned type will be
> "struct page **". These are the same allocation size (pointer size), but
> the types don't match. Adjust the allocation type to match the assignment.
> 
> Signed-off-by: Kees Cook <kees@kernel.org>

Added to for-next, thanks.

Re: [PATCH] btrfs: compression: Adjust cb->compressed_folios allocation type

[Kees Cook]

On Sat, Apr 26, 2025 at 12:55:21AM -0600, Gustavo A. R. Silva wrote:
> 
> 
> On 26/04/25 00:23, Kees Cook wrote:
> > In preparation for making the kmalloc family of allocators type aware,
> > we need to make sure that the returned type from the allocation matches
> > the type of the variable being assigned. (Before, the allocator would
> > always return "void *", which can be implicitly cast to any pointer type.)
> > 
> > The assigned type is "struct folio **" but the returned type will be
> > "struct page **". These are the same allocation size (pointer size), but
> > the types don't match. Adjust the allocation type to match the assignment.
> > 
> > Signed-off-by: Kees Cook <kees@kernel.org>
> > ---
> > Cc: Chris Mason <clm@fb.com>
> > Cc: Josef Bacik <josef@toxicpanda.com>
> > Cc: David Sterba <dsterba@suse.com>
> > Cc: <linux-btrfs@vger.kernel.org>
> > ---
> >   fs/btrfs/compression.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
> > index e7f8ee5d48a4..7f11ef559be6 100644
> > --- a/fs/btrfs/compression.c
> > +++ b/fs/btrfs/compression.c
> > @@ -606,7 +606,7 @@ void btrfs_submit_compressed_read(struct btrfs_bio *bbio)
> >   	free_extent_map(em);
> >   	cb->nr_folios = DIV_ROUND_UP(compressed_len, PAGE_SIZE);
> > -	cb->compressed_folios = kcalloc(cb->nr_folios, sizeof(struct page *), GFP_NOFS);
> > +	cb->compressed_folios = kcalloc(cb->nr_folios, sizeof(struct folio *), GFP_NOFS);
> 
> Why not `sizeof(*cb->compressed_folios)` as in other patches? :)

I generally trying to match the coding style of each instance, though
sometimes it wasn't possible. Here, since a type is named for the
sizeof(), I followed that style.

-- 
Kees Cook