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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: Kees Cook <keescook@chromium.org>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Kees Cook 2018-05-29 16:44:59 -07:00 committed by David Sterba
parent 090a127afa
commit 1389053e1b
1 changed files with 28 additions and 10 deletions
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38
fs/btrfs/raid56.c
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@ -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;