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

This is back ported from upstream directly.

commit c2c1b089b44b783bd50fae4bccaa6f367f92e492
Author: Zhang Yanfei <[email protected]>
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.

    [[email protected]: avoid `if (foo = bar)' thing, use min_t()]
    [[email protected]: s/max_t/min_t/]
    Signed-off-by: Zhang Yanfei <[email protected]>
    Cc: "Eric W. Biederman" <[email protected]>
    Signed-off-by: Andrew Morton <[email protected]>
    Signed-off-by: Linus Torvalds <[email protected]>

Signed-off-by: Baoquan He <[email protected]>
---
 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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