mm: add a gfp-translate script to help understand page allocation failure reports

The page allocation failure messages include a line that looks like

page allocation failure. order:1, mode:0x4020

The mode is easy to translate but irritating for the lazy and a bit error
prone.  This patch adds a very simple helper script gfp-translate for the
mode: portion of the page allocation failure messages.  An example usage
looks like

  mel@machina:~/linux-2.6 $ scripts/gfp-translate 0x4020
  Source: /home/mel/linux-2.6
  Parsing: 0x4020
  #define __GFP_HIGH	(0x20)	/* Should access emergency pools? */
  #define __GFP_COMP	(0x4000) /* Add compound page metadata */

The script is not a work of art but it has come in handy for me a few
times so I thought I would share.

[akpm@linux-foundation.org: clarify an error message]
Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Minchan Kim <minchan.kim@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/scripts/gfp-translate b/scripts/gfp-translate
new file mode 100644 (file)
index 0000000..073cb6d
--- /dev/null
+++ b/scripts/gfp-translate
@@ -0,0 +1,81 @@
+#!/bin/bash
+# Translate the bits making up a GFP mask
+# (c) 2009, Mel Gorman <mel@csn.ul.ie>
+# Licensed under the terms of the GNU GPL License version 2
+SOURCE=
+GFPMASK=none
+
+# Helper function to report failures and exit
+die() {
+       echo ERROR: $@
+       if [ "$TMPFILE" != "" ]; then
+               rm -f $TMPFILE
+       fi
+       exit -1
+}
+
+usage() {
+       echo "usage: gfp-translate [-h] [ --source DIRECTORY ] gfpmask"
+       exit 0
+}
+
+# Parse command-line arguements
+while [ $# -gt 0 ]; do
+       case $1 in
+               --source)
+                       SOURCE=$2
+                       shift 2
+                       ;;
+               -h)
+                       usage
+                       ;;
+               --help)
+                       usage
+                       ;;
+               *)
+                       GFPMASK=$1
+                       shift
+                       ;;
+       esac
+done
+
+# Guess the kernel source directory if it's not set. Preference is in order of
+# o current directory
+# o /usr/src/linux
+if [ "$SOURCE" = "" ]; then
+       if [ -r "/usr/src/linux/Makefile" ]; then
+               SOURCE=/usr/src/linux
+       fi
+       if [ -r "`pwd`/Makefile" ]; then
+               SOURCE=`pwd`
+       fi
+fi
+
+# Confirm that a source directory exists
+if [ ! -r "$SOURCE/Makefile" ]; then
+       die "Could not locate kernel source directory or it is invalid"
+fi
+
+# Confirm that a GFP mask has been specified
+if [ "$GFPMASK" = "none" ]; then
+       usage
+fi
+
+# Extract GFP flags from the kernel source
+TMPFILE=`mktemp -t gfptranslate-XXXXXX` || exit 1
+grep "^#define __GFP" $SOURCE/include/linux/gfp.h | sed -e 's/(__force gfp_t)//' | sed -e 's/u)/)/' | grep -v GFP_BITS | sed -e 's/)\//) \//' > $TMPFILE
+
+# Parse the flags
+IFS="
+"
+echo Source: $SOURCE
+echo Parsing: $GFPMASK
+for LINE in `cat $TMPFILE`; do
+       MASK=`echo $LINE | awk '{print $3}'`
+       if [ $(($GFPMASK&$MASK)) -ne 0 ]; then
+               echo $LINE
+       fi
+done
+
+rm -f $TMPFILE
+exit 0