Re: [PATCH 10/17] jbd2: replace __get_free_pages() with kmalloc()

[David Laight <david.laight.linux@gmail.com>]

On Mon, 25 May 2026 18:17:04 +0200
Jan Kara <jack@suse.cz> wrote:

> On Sat 23-05-26 20:54:22, Mike Rapoport (Microsoft) wrote:
> > jbd2_alloc() falls back from kmem_cache_alloc() to __get_free_pages() for
> > allocations larger than PAGE_SIZE.
> > But kmalloc() can handle such cases with essentially the same fallback.
> > 
> > Replace use of __get_free_pages() with kmalloc() and simplify
> > jbd2_free() as both kmem_cache_alloc() and kmalloc() allocations can be
> > freed with kfree().
> > 
> > Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>  
> 
> Looks good. Feel free to add:
> 
> Reviewed-by: Jan Kara <jack@suse.cz>
> 
> I'll just note that we allocate here fs block size large buffer so the same
> kind of allocator as we use for folios would be even better. But that's a
> different cleanup I guess.

Would kvalloc() be more appropriate here?
Does __get_free_pages() return physically contiguous memory?

-- David

> 
> 								Honza
> 
> > ---
> >  fs/jbd2/journal.c | 7 ++-----
> >  1 file changed, 2 insertions(+), 5 deletions(-)
> > 
> > diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
> > index 4f397fcdb13c..1137b471e490 100644
> > --- a/fs/jbd2/journal.c
> > +++ b/fs/jbd2/journal.c
> > @@ -2784,7 +2784,7 @@ void *jbd2_alloc(size_t size, gfp_t flags)
> >  	if (size < PAGE_SIZE)
> >  		ptr = kmem_cache_alloc(get_slab(size), flags);
> >  	else
> > -		ptr = (void *)__get_free_pages(flags, get_order(size));
> > +		ptr = kmalloc(size, flags);
> >  
> >  	/* Check alignment; SLUB has gotten this wrong in the past,
> >  	 * and this can lead to user data corruption! */
> > @@ -2795,10 +2795,7 @@ void *jbd2_alloc(size_t size, gfp_t flags)
> >  
> >  void jbd2_free(void *ptr, size_t size)
> >  {
> > -	if (size < PAGE_SIZE)
> > -		kmem_cache_free(get_slab(size), ptr);
> > -	else
> > -		free_pages((unsigned long)ptr, get_order(size));
> > +	kfree(ptr);
> >  };
> >  
> >  /*
> > 
> > -- 
> > 2.53.0
> >