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Commit 1389053e authored by Kees Cook's avatar Kees Cook Committed by David Sterba
Browse files

btrfs: raid56: Remove VLA usage 

In the quest to remove all stack VLA usage from the kernel[1], this
allocates the working buffers during regular init, instead of using stack
space. This refactors the allocation code a bit to make it easier
to review.

[1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com



Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 090a127a

fs/btrfs/raid56.c

+28 −10
Original line number Diff line number Diff line
@@ -163,6 +163,12 @@ struct btrfs_raid_bio { 
	 * bitmap to record which horizontal stripe has data

	 */

	unsigned long *dbitmap;



	/* allocated with real_stripes-many pointers for finish_*() calls */

	void **finish_pointers;



	/* allocated with stripe_npages-many bits for finish_*() calls */

	unsigned long *finish_pbitmap;

};



static int __raid56_parity_recover(struct btrfs_raid_bio *rbio);
@@ -981,9 +987,14 @@ static struct btrfs_raid_bio *alloc_rbio(struct btrfs_fs_info *fs_info, 
	int stripe_npages = DIV_ROUND_UP(stripe_len, PAGE_SIZE);

	void *p;



	rbio = kzalloc(sizeof(*rbio) + num_pages * sizeof(struct page *) * 2 +

		       DIV_ROUND_UP(stripe_npages, BITS_PER_LONG) *

		       sizeof(long), GFP_NOFS);

	rbio = kzalloc(sizeof(*rbio) +

		       sizeof(*rbio->stripe_pages) * num_pages +

		       sizeof(*rbio->bio_pages) * num_pages +

		       sizeof(*rbio->finish_pointers) * real_stripes +

		       sizeof(*rbio->dbitmap) * BITS_TO_LONGS(stripe_npages) +

		       sizeof(*rbio->finish_pbitmap) *

				BITS_TO_LONGS(stripe_npages),

		       GFP_NOFS);

	if (!rbio)

		return ERR_PTR(-ENOMEM);
@@ -1005,13 +1016,20 @@ static struct btrfs_raid_bio *alloc_rbio(struct btrfs_fs_info *fs_info, 
	atomic_set(&rbio->stripes_pending, 0);



	/*

	 * the stripe_pages and bio_pages array point to the extra

	 * the stripe_pages, bio_pages, etc arrays point to the extra

	 * memory we allocated past the end of the rbio

	 */

	p = rbio + 1;

	rbio->stripe_pages = p;

	rbio->bio_pages = p + sizeof(struct page *) * num_pages;

	rbio->dbitmap = p + sizeof(struct page *) * num_pages * 2;

#define CONSUME_ALLOC(ptr, count)	do {				\

		ptr = p;						\

		p = (unsigned char *)p + sizeof(*(ptr)) * (count);	\

	} while (0)

	CONSUME_ALLOC(rbio->stripe_pages, num_pages);

	CONSUME_ALLOC(rbio->bio_pages, num_pages);

	CONSUME_ALLOC(rbio->finish_pointers, real_stripes);

	CONSUME_ALLOC(rbio->dbitmap, BITS_TO_LONGS(stripe_npages));

	CONSUME_ALLOC(rbio->finish_pbitmap, BITS_TO_LONGS(stripe_npages));

#undef  CONSUME_ALLOC



	if (bbio->map_type & BTRFS_BLOCK_GROUP_RAID5)

		nr_data = real_stripes - 1;
@@ -1180,7 +1198,7 @@ static void index_rbio_pages(struct btrfs_raid_bio *rbio) 
static noinline void finish_rmw(struct btrfs_raid_bio *rbio)

{

	struct btrfs_bio *bbio = rbio->bbio;

	void *pointers[rbio->real_stripes];

	void **pointers = rbio->finish_pointers;

	int nr_data = rbio->nr_data;

	int stripe;

	int pagenr;
@@ -2350,8 +2368,8 @@ static noinline void finish_parity_scrub(struct btrfs_raid_bio *rbio, 
					 int need_check)

{

	struct btrfs_bio *bbio = rbio->bbio;

	void *pointers[rbio->real_stripes];

	DECLARE_BITMAP(pbitmap, rbio->stripe_npages);

	void **pointers = rbio->finish_pointers;

	unsigned long *pbitmap = rbio->finish_pbitmap;

	int nr_data = rbio->nr_data;

	int stripe;

	int pagenr;