linux-kernel - [RHEL6.8 Patch 04/19] fs/proc/vmcore.c: put if tests in the top of the while loop to reduce duplication

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Date:	Thu, 16 Jul 2015 16:47:02 +0800
From:	Baoquan He <bhe@...hat.com>
To:	linux-kernel@...r.kernel.org, ncroxon@...hat.com,
	dyoung@...hat.com, mhuang@...hat.com
Cc:	Baoquan He <bhe@...hat.com>
Subject: [RHEL6.8 Patch 04/19] fs/proc/vmcore.c: put if tests in the top of the while loop to reduce duplication

Resolves: bz1097904
https://bugzilla.redhat.com/show_bug.cgi?id=1097904

This is back ported from upstream directly.

commit c2c1b089b44b783bd50fae4bccaa6f367f92e492
Author: Zhang Yanfei <zhangyanfei@...fujitsu.com>
Date:   Wed Feb 27 17:03:17 2013 -0800

    fs/proc/vmcore.c: put if tests in the top of the while loop to reduce duplication

    In read_vmcore() two `if' tests are duplicated.  Change the position of
    them could reduce the duplication.  This change does not affect the
    behaviour of the function.

    [akpm@...ux-foundation.org: avoid `if (foo = bar)' thing, use min_t()]
    [akpm@...ux-foundation.org: s/max_t/min_t/]
    Signed-off-by: Zhang Yanfei <zhangyanfei@...fujitsu.com>
    Cc: "Eric W. Biederman" <ebiederm@...ssion.com>
    Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>

Signed-off-by: Baoquan He <bhe@...hat.com>
---
 fs/proc/vmcore.c | 20 +++++++-------------
 1 file changed, 7 insertions(+), 13 deletions(-)

diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index ce23082..1def40a 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -173,15 +173,15 @@ static ssize_t read_vmcore(struct file *file, char __user *buffer,
 	start = map_offset_to_paddr(*fpos, &vmcore_list, &curr_m);
 	if (!curr_m)
         	return -EINVAL;
-	if ((tsz = (PAGE_SIZE - (start & ~PAGE_MASK))) > buflen)
-		tsz = buflen;
-
-	/* Calculate left bytes in current memory segment. */
-	nr_bytes = (curr_m->size - (start - curr_m->paddr));
-	if (tsz > nr_bytes)
-		tsz = nr_bytes;
 
 	while (buflen) {
+		tsz = min_t(size_t, buflen, PAGE_SIZE - (start & ~PAGE_MASK));
+
+		/* Calculate left bytes in current memory segment. */
+		nr_bytes = (curr_m->size - (start - curr_m->paddr));
+		if (tsz > nr_bytes)
+			tsz = nr_bytes;
+
 		tmp = read_from_oldmem(buffer, tsz, &start, 1);
 		if (tmp < 0)
 			return tmp;
@@ -196,12 +196,6 @@ static ssize_t read_vmcore(struct file *file, char __user *buffer,
 						struct vmcore, list);
 			start = curr_m->paddr;
 		}
-		if ((tsz = (PAGE_SIZE - (start & ~PAGE_MASK))) > buflen)
-			tsz = buflen;
-		/* Calculate left bytes in current memory segment. */
-		nr_bytes = (curr_m->size - (start - curr_m->paddr));
-		if (tsz > nr_bytes)
-			tsz = nr_bytes;
 	}
 	return acc;
 }
-- 
2.1.0

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