Re: [RFC PATCH v2 04/16] iomap: add async buffered write support

[Stefan Roesch <shr@fb.com>]

On 5/17/22 4:14 AM, Jan Kara wrote:
> On Mon 16-05-22 09:47:06, Stefan Roesch wrote:
>> This adds async buffered write support to iomap. The support is focused
>> on the changes necessary to support XFS with iomap.
>>
>> Support for other filesystems might require additional changes.
>>
>> Signed-off-by: Stefan Roesch <shr@fb.com>
>> ---
>>  fs/iomap/buffered-io.c | 21 ++++++++++++++++++++-
>>  1 file changed, 20 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
>> index 1ffdc7078e7d..ceb3091f94c2 100644
>> --- a/fs/iomap/buffered-io.c
>> +++ b/fs/iomap/buffered-io.c
>> @@ -580,13 +580,20 @@ static int __iomap_write_begin(const struct iomap_iter *iter, loff_t pos,
>>  	size_t from = offset_in_folio(folio, pos), to = from + len;
>>  	size_t poff, plen;
>>  	gfp_t  gfp = GFP_NOFS | __GFP_NOFAIL;
>> +	bool no_wait = (iter->flags & IOMAP_NOWAIT);
>> +
>> +	if (no_wait)
>> +		gfp = GFP_NOIO;
> 
> GFP_NOIO means that direct reclaim is still allowed. Not sure whether you
> want to enter direct reclaim from io_uring fast path because in theory that
> can still sleep. GFP_NOWAIT would be a more natural choice...

I'll change it to GFP_NOWAIT in the next version of the patch series.
> 
> 								Honza