Re: [PATCH] jbd2: get rid of superfluous __GFP_REPEAT

From: Theodore Ts'o
Date: Sun Nov 08 2015 - 00:08:17 EST

On Sat, Nov 07, 2015 at 10:22:55AM +0900, Tetsuo Handa wrote:
> All jbd2_alloc() callers seem to pass GFP_NOFS. Therefore, use of
> vmalloc() which implicitly passes GFP_KERNEL | __GFP_HIGHMEM can cause
> deadlock, can't it? This vmalloc(size) call needs to be replaced with
> __vmalloc(size, flags).

jbd2_alloc is only passed in the bh->b_size, which can't be >
PAGE_SIZE, so the code path that calls vmalloc() should never get
called. When we conveted jbd2_alloc() to suppor sub-page size
allocations in commit d2eecb039368, there was an assumption that it
could be called with a size greater than PAGE_SIZE, but that's
certaily not true today.

- Ted
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