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: Omar Sandoval <osandov@fb.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/free-space-tree.c b/fs/btrfs/free-space-tree.c
index c7397b0..a5e34de 100644
--- a/fs/btrfs/free-space-tree.c
+++ b/fs/btrfs/free-space-tree.c
@@ -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,