Thread (13 messages) 13 messages, 2 authors, 2012-03-08

Re: [PATCH 3/5] hugetlb: try to search again if it is really needed

From: Andrew Morton <akpm@linux-foundation.org>
Date: 2012-02-01 22:43:56
Also in: lkml

On Fri, 13 Jan 2012 19:45:45 +0800
Xiao Guangrong [off-list ref] wrote:
quoted hunk ↗ jump to hunk
Search again only if some holes may be skipped in the first time

Signed-off-by: Xiao Guangrong <redacted>
---
 arch/x86/mm/hugetlbpage.c |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/arch/x86/mm/hugetlbpage.c b/arch/x86/mm/hugetlbpage.c
index e12debc..6bf5735 100644
--- a/arch/x86/mm/hugetlbpage.c
+++ b/arch/x86/mm/hugetlbpage.c
@@ -309,9 +309,8 @@ static unsigned long hugetlb_get_unmapped_area_topdown(struct file *file,
 	struct hstate *h = hstate_file(file);
 	struct mm_struct *mm = current->mm;
 	struct vm_area_struct *vma;
-	unsigned long base = mm->mmap_base, addr = addr0;
+	unsigned long base = mm->mmap_base, addr = addr0, start_addr;
grr.  The multiple-definitions-per-line thing is ugly, makes for more
patch conflicts and reduces opportunities to add useful comments.
--- a/arch/x86/mm/hugetlbpage.c~hugetlb-try-to-search-again-if-it-is-really-needed-fix
+++ a/arch/x86/mm/hugetlbpage.c
@@ -309,7 +309,9 @@ static unsigned long hugetlb_get_unmappe
 	struct hstate *h = hstate_file(file);
 	struct mm_struct *mm = current->mm;
 	struct vm_area_struct *vma;
-	unsigned long base = mm->mmap_base, addr = addr0, start_addr;
+	unsigned long base = mm->mmap_base;
+	unsigned long addr = addr0;
+	unsigned long start_addr;
 	unsigned long largest_hole = mm->cached_hole_size;
 
 	/* don't allow allocations above current base */
_

quoted hunk ↗ jump to hunk
 	unsigned long largest_hole = mm->cached_hole_size;
-	int first_time = 1;

 	/* don't allow allocations above current base */
 	if (mm->free_area_cache > base)
@@ -322,6 +321,8 @@ static unsigned long hugetlb_get_unmapped_area_topdown(struct file *file,
 		mm->free_area_cache  = base;
 	}
 try_again:
+	start_addr = mm->free_area_cache;
+
 	/* make sure it can fit in the remaining address space */
 	if (mm->free_area_cache < len)
 		goto fail;
@@ -357,10 +358,9 @@ fail:
 	 * if hint left us with no space for the requested
 	 * mapping then try again:
 	 */
-	if (first_time) {
+	if (start_addr != base) {
 		mm->free_area_cache = base;
 		largest_hole = 0;
-		first_time = 0;
 		goto try_again;
The code used to retry a single time.  With this change the retrying is
potentially infinite.  What is the reason for this change?  What is the
potential for causing a lockup?

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