linux-kernel - Re: [PATCH V4 1/6] mm: delete unnecessary TTU

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Message-ID: <20170223153534.GA4031@cmpxchg.org>
Date:   Thu, 23 Feb 2017 10:35:34 -0500
From:   Johannes Weiner <hannes@...xchg.org>
To:     Shaohua Li <shli@...com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Kernel-team@...com, mhocko@...e.com, minchan@...nel.org,
        hughd@...gle.com, riel@...hat.com, mgorman@...hsingularity.net,
        akpm@...ux-foundation.org
Subject: Re: [PATCH V4 1/6] mm: delete unnecessary TTU_* flags

On Wed, Feb 22, 2017 at 10:50:39AM -0800, Shaohua Li wrote:
> Johannes pointed out TTU_LZFREE is unnecessary. It's true because we
> always have the flag set if we want to do an unmap. For cases we don't
> do an unmap, the TTU_LZFREE part of code should never run.
> 
> Also the TTU_UNMAP is unnecessary. If no other flags set (for
> example, TTU_MIGRATION), an unmap is implied.
> 
> Cc: Michal Hocko <mhocko@...e.com>
> Cc: Minchan Kim <minchan@...nel.org>
> Cc: Hugh Dickins <hughd@...gle.com>
> Cc: Rik van Riel <riel@...hat.com>
> Cc: Mel Gorman <mgorman@...hsingularity.net>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Suggested-by: Johannes Weiner <hannes@...xchg.org>
> Signed-off-by: Shaohua Li <shli@...com>

Thanks!

Acked-by: Johannes Weiner <hannes@...xchg.org>

> @@ -83,10 +83,8 @@ struct anon_vma_chain {
>  };
>  
>  enum ttu_flags {
> -	TTU_UNMAP = 1,			/* unmap mode */
>  	TTU_MIGRATION = 2,		/* migration mode */
>  	TTU_MUNLOCK = 4,		/* munlock mode */
> -	TTU_LZFREE = 8,			/* lazy free mode */
>  	TTU_SPLIT_HUGE_PMD = 16,	/* split huge PMD if any */
>  
>  	TTU_IGNORE_MLOCK = (1 << 8),	/* ignore mlock */

This on top?

---
Subject: [PATCH] mm: delete unnecessary TTU_* flags fix

Clean up the TTU flags a bit. Remove dead TTU_ACTION macro.

Signed-off-by: Johannes Weiner <hannes@...xchg.org>
---

diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 70ef7536c088..640214bc4635 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -82,17 +82,17 @@ struct anon_vma_chain {
 };
 
 enum ttu_flags {
-	TTU_MIGRATION = 2,		/* migration mode */
-	TTU_MUNLOCK = 4,		/* munlock mode */
-	TTU_SPLIT_HUGE_PMD = 16,	/* split huge PMD if any */
-
-	TTU_IGNORE_MLOCK = (1 << 8),	/* ignore mlock */
-	TTU_IGNORE_ACCESS = (1 << 9),	/* don't age */
-	TTU_IGNORE_HWPOISON = (1 << 10),/* corrupted page is recoverable */
-	TTU_BATCH_FLUSH = (1 << 11),	/* Batch TLB flushes where possible
+	TTU_MIGRATION		= 0x1,	/* migration mode */
+	TTU_MUNLOCK		= 0x2,	/* munlock mode */
+
+	TTU_SPLIT_HUGE_PMD	= 0x4,	/* split huge PMD if any */
+	TTU_IGNORE_MLOCK	= 0x8,	/* ignore mlock */
+	TTU_IGNORE_ACCESS	= 0x10,	/* don't age */
+	TTU_IGNORE_HWPOISON	= 0x20,	/* corrupted page is recoverable */
+	TTU_BATCH_FLUSH		= 0x40,	/* Batch TLB flushes where possible
 					 * and caller guarantees they will
 					 * do a final flush if necessary */
-	TTU_RMAP_LOCKED = (1 << 12)	/* do not grab rmap lock:
+	TTU_RMAP_LOCKED		= 0x80	/* do not grab rmap lock:
 					 * caller holds it */
 };
 
@@ -182,8 +182,6 @@ static inline void page_dup_rmap(struct page *page, bool compound)
 int page_referenced(struct page *, int is_locked,
 			struct mem_cgroup *memcg, unsigned long *vm_flags);
 
-#define TTU_ACTION(x) ((x) & TTU_ACTION_MASK)
-
 int try_to_unmap(struct page *, enum ttu_flags flags);
 
 /*