Re: [f2fs-dev] [PATCH] f2fs: don't return vmalloc() memory from f2fs_kmalloc()

[Chao Yu <yuchao0@huawei.com>]

On 2020/5/7 2:43, Eric Biggers wrote:
> On Wed, May 06, 2020 at 03:43:36PM +0800, Chao Yu wrote:
>> On 2020/5/6 4:48, Eric Biggers wrote:
>>> From: Eric Biggers <ebiggers@google.com>
>>>
>>> kmalloc() returns kmalloc'ed memory, and kvmalloc() returns either
>>> kmalloc'ed or vmalloc'ed memory.  But the f2fs wrappers, f2fs_kmalloc()
>>> and f2fs_kvmalloc(), both return both kinds of memory.
>>>
>>> It's redundant to have two functions that do the same thing, and also
>>> breaking the standard naming convention is causing bugs since people
>>> assume it's safe to kfree() memory allocated by f2fs_kmalloc().  See
>>> e.g. the various allocations in fs/f2fs/compress.c.
>>>
>>> Fix this by making f2fs_kmalloc() just use kmalloc().  And to avoid
>>> re-introducing the allocation failures that the vmalloc fallback was
>>> intended to fix, convert the largest allocations to use f2fs_kvmalloc().
>>
>> I've submitted one patch since you suggested when commented in compression
>> support patch.
>>
>> I remember Jaegeuk prefer to use f2fs_kvmalloc() to instead f2fs_kmalloc(),
>> and keep the order of kmalloc - failed - kvmalloc.
>>
> 
> I think you're talking about
> https://lkml.kernel.org/r/20191105030451.GA55090@jaegeuk-macbookpro.roam.corp.google.com?
> 
> I think that making the large allocations use kvmalloc(), as this patch does, is
> good enough to address any memory allocation failures that may have been
> encountered in the past.  We don't need to switch all allocations to use
> kvmalloc(), as there's no benefit for small allocations.

Yeah, I agreed, and in ENOMEM case, small-sized kvmalloc increases allocating path
length unnecessarily.

Thanks,

> 
> - Eric
> .
> 


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