Re: [RFC PATCH] memalloc_noio: update the comment to make it cleaner

From: Xiubo Li
Date: Wed Sep 18 2019 - 04:03:01 EST


On 2019/9/18 15:25, Michal Hocko wrote:
On Wed 18-09-19 04:58:20, xiubli@xxxxxxxxxx wrote:
From: Xiubo Li <xiubli@xxxxxxxxxx>

The GFP_NOIO means all further allocations will implicitly drop
both __GFP_IO and __GFP_FS flags and so they are safe for both the
IO critical section and the the critical section from the allocation
recursion point of view. Not only the __GFP_IO, which a bit confusing
when reading the code or using the save/restore pair.
Historically GFP_NOIO has always implied GFP_NOFS as well. I can imagine
that this might come as an surprise for somebody not familiar with the
code though.

Yeah, it true.

I am wondering whether your update of the documentation
would be better off at __GFP_FS, __GFP_IO resp. GFP_NOFS, GFP_NOIO level.
This interface is simply a way to set a scoped NO{IO,FS} context.

The "Documentation/core-api/gfp_mask-from-fs-io.rst" is already very detail about them all.

This fixing just means to make sure that it won't surprise someone who is having a quickly through some code and not familiar much about the detail. It may make not much sense ?

Thanks,
BRs
Xiubo


Signed-off-by: Xiubo Li <xiubli@xxxxxxxxxx>
---
include/linux/sched/mm.h | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
index 4a7944078cc3..9bdc97e52de1 100644
--- a/include/linux/sched/mm.h
+++ b/include/linux/sched/mm.h
@@ -211,10 +211,11 @@ static inline void fs_reclaim_release(gfp_t gfp_mask) { }
* memalloc_noio_save - Marks implicit GFP_NOIO allocation scope.
*
* This functions marks the beginning of the GFP_NOIO allocation scope.
- * All further allocations will implicitly drop __GFP_IO flag and so
- * they are safe for the IO critical section from the allocation recursion
- * point of view. Use memalloc_noio_restore to end the scope with flags
- * returned by this function.
+ * All further allocations will implicitly drop __GFP_IO and __GFP_FS
+ * flags and so they are safe for both the IO critical section and the
+ * the critical section from the allocation recursion point of view. Use
+ * memalloc_noio_restore to end the scope with flags returned by this
+ * function.
*
* This function is safe to be used from any context.
*/
--
2.21.0