Re: [PATCH V2] fuse: Remove __GFP_FS flag to avoid allocator recursing

From: ppvk@codeaurora.org
To: Matthew Wilcox <willy@infradead.org>
Cc: miklos@szeredi.hu, linux-fsdevel@vger.kernel.org,
	stummala@codeaurora.org, sayalil@codeaurora.org
Subject: Re: [PATCH V2] fuse: Remove __GFP_FS flag to avoid allocator recursing
Date: Mon, 21 Sep 2020 17:09:00 +0530	[thread overview]
Message-ID: <2a5b17f0a80d6a52e6c2c7301dea4c41@codeaurora.org> (raw)
In-Reply-To: <20200916145634.GN5449@casper.infradead.org>

On 2020-09-16 20:26, Matthew Wilcox wrote:
> On Wed, Sep 16, 2020 at 12:09:40PM +0530, Pradeep P V K wrote:
>> Changes since V1:
>> - Used memalloc_nofs_save() in all allocation paths of fuse daemons
>>   to avoid use __GFP_FS flag as per Matthew comments.
> 
> That's not how to use memalloc_nofs_save().  You call it when entering 
> a
> context in which any memory allocation would cause a deadlock.  You 
> don't
> look for every place which allocates memory and wrap the memory 
> allocation
> calls in memalloc_nofs_save() because you're likely to miss one.

> ok, i will fix this in my next patch set.
>>  static ssize_t fuse_dev_read(struct kiocb *iocb, struct iov_iter *to)
>>  {
>> +	ssize_t size;
>> +	unsigned nofs_flag;
> 
> This is almost certainly too low in the call stack.
ok, i will update this in my next patch set.