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Commit 25ff17e8 authored by Omar Sandoval's avatar Omar Sandoval Committed by David Sterba
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Btrfs: use memalloc_nofs and kvzalloc() for free space tree bitmaps 



First, instead of open-coding the vmalloc() fallback, use the new
kvzalloc() helper. Second, use memalloc_nofs_{save,restore}() instead of
GFP_NOFS, as vmalloc() uses some GFP_KERNEL allocations internally which
could lead to deadlocks.

Signed-off-by: default avatarOmar Sandoval <osandov@fb.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 4b5faeac

fs/btrfs/free-space-tree.c

+13 −13
Original line number Diff line number Diff line
@@ -17,7 +17,7 @@ 
 */



#include <linux/kernel.h>

#include <linux/vmalloc.h>

#include <linux/sched/mm.h>

#include "ctree.h"

#include "disk-io.h"

#include "locking.h"
@@ -153,21 +153,21 @@ static inline u32 free_space_bitmap_size(u64 size, u32 sectorsize) 


static u8 *alloc_bitmap(u32 bitmap_size)

{

	void *mem;

	u8 *ret;

	unsigned int nofs_flag;



	/*

	 * The allocation size varies, observed numbers were < 4K up to 16K.

	 * Using vmalloc unconditionally would be too heavy, we'll try

	 * contiguous allocations first.

	 * GFP_NOFS doesn't work with kvmalloc(), but we really can't recurse

	 * into the filesystem as the free space bitmap can be modified in the

	 * critical section of a transaction commit.

	 *

	 * TODO: push the memalloc_nofs_{save,restore}() to the caller where we

	 * know that recursion is unsafe.

	 */

	if  (bitmap_size <= PAGE_SIZE)

		return kzalloc(bitmap_size, GFP_NOFS);



	mem = kzalloc(bitmap_size, GFP_NOFS | __GFP_NOWARN);

	if (mem)

		return mem;



	return __vmalloc(bitmap_size, GFP_NOFS | __GFP_ZERO, PAGE_KERNEL);

	nofs_flag = memalloc_nofs_save();

	ret = kvzalloc(bitmap_size, GFP_KERNEL);

	memalloc_nofs_restore(nofs_flag);

	return ret;

}



int convert_free_space_to_bitmaps(struct btrfs_trans_handle *trans,