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SubjectRe: [PATCH] page-types: decode flags directly from command line
Hi Alex,

On Wed, Nov 04, 2009 at 06:54:41AM +0800, Alex Chiang wrote:
> Teach page-types to decode page flags directly from the command
> line.

This is good feature to have - I considered adding it, too ;)

>
> Why is this useful? For instance, if you're using memory hotplug
> and see this in /var/log/messages:
>
> kernel: removing from LRU failed 3836dd0/1/1e00000000000400
>
> It would be nice to decode those page flags without staring at
> the source.

In fact it's more than decode - encoding is also possible with the
_same_ code! So maybe "-d" and help message will not be all that
appropriate.

> Example usage and output:
>
> linux-2.6/Documentation/vm$ ./page-types -d 0x1e00000000000400
> flags page-count MB symbolic-flags long-symbolic-flags
> 0x1e00000000000400 1 0 __________B_______________________buddy
> total 1 0

The output is a bit redundant - so does the code. Could you simplify
them a bit?

Thanks,
Fengguang

> Signed-off-by: Alex Chiang <achiang@hp.com>
> ---
> page-types.c | 26 ++++++++++++++++++++++++--
> 1 file changed, 24 insertions(+), 2 deletions(-)
> ---
> diff --git a/Documentation/vm/page-types.c b/Documentation/vm/page-types.c
> index 3ec4f2a..a55c624 100644
> --- a/Documentation/vm/page-types.c
> +++ b/Documentation/vm/page-types.c
> @@ -674,6 +674,7 @@ static void usage(void)
> printf(
> "page-types [options]\n"
> " -r|--raw Raw mode, for kernel developers\n"
> +" -d|--decode flags Decode a single page's flags\n"
> " -a|--addr addr-spec Walk a range of pages\n"
> " -b|--bits bits-spec Walk pages with specified bits\n"
> " -p|--pid pid Walk process address space\n"
> @@ -682,10 +683,12 @@ static void usage(void)
> #endif
> " -l|--list Show page details in ranges\n"
> " -L|--list-each Show page details one by one\n"
> -" -N|--no-summary Don't show summay info\n"
> +" -N|--no-summary Don't show summary info\n"
> " -X|--hwpoison hwpoison pages\n"
> " -x|--unpoison unpoison pages\n"
> " -h|--help Show this usage message\n"
> +"flags:\n"
> +" 0x0000000000000400 A single page's flags, e.g.\n"
> "addr-spec:\n"
> " N one page at offset N (unit: pages)\n"
> " N+M pages range from N to N+M-1\n"
> @@ -884,12 +887,28 @@ static void parse_bits_mask(const char *optarg)
> add_bits_filter(mask, bits);
> }
>
> +static void decode_flags_and_exit(const char *optarg)
> +{
> + uint64_t flags;
> +
> + flags = parse_number(optarg);
> +
> + opt_list = 0;
> + opt_hwpoison = 0;
> + opt_unpoison = 0;
> +
> + add_page(0, 0, flags);
> + show_summary();
> +
> + exit(0);
> +}
>
> static struct option opts[] = {
> { "raw" , 0, NULL, 'r' },
> { "pid" , 1, NULL, 'p' },
> { "file" , 1, NULL, 'f' },
> { "addr" , 1, NULL, 'a' },
> + { "decode" , 1, NULL, 'd' },
> { "bits" , 1, NULL, 'b' },
> { "list" , 0, NULL, 'l' },
> { "list-each" , 0, NULL, 'L' },
> @@ -907,7 +926,7 @@ int main(int argc, char *argv[])
> page_size = getpagesize();
>
> while ((c = getopt_long(argc, argv,
> - "rp:f:a:b:lLNXxh", opts, NULL)) != -1) {
> + "rp:f:a:b:d:lLNXxh", opts, NULL)) != -1) {
> switch (c) {
> case 'r':
> opt_raw = 1;
> @@ -924,6 +943,9 @@ int main(int argc, char *argv[])
> case 'b':
> parse_bits_mask(optarg);
> break;
> + case 'd':
> + decode_flags_and_exit(optarg);
> + break;
> case 'l':
> opt_list = 1;
> break;


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