lkml.org 
[lkml]   [2018]   [May]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH] 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>
---
fs/btrfs/raid56.c | 38 ++++++++++++++++++++++++++++----------
1 file changed, 28 insertions(+), 10 deletions(-)

diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
index 9abd950e7f78..5e4ad134b9ad 100644
--- a/fs/btrfs/raid56.c
+++ b/fs/btrfs/raid56.c
@@ -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;
--
2.17.0

--
Kees Cook
Pixel Security

\
 
 \ /
  Last update: 2018-05-30 01:45    [W:0.050 / U:2.612 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site