tytso@xxxxxxx wrote:
> Ok, how about this, for even more explicit?
>
> - Ted
Sure, that looks even better. Who knew args parsing was so hard ;)
-Eric
> commit 15121c18a22ae483279f76dc9e554334b800d0f7
> Author: Eric Sandeen <sandeen@xxxxxxxxxx>
> Date: Mon Feb 15 20:17:55 2010 -0500
>
> ext4: Fix optional-arg mount options
>
> We have 2 mount options, "barrier" and "auto_da_alloc" which may or
> may not take a 1/0 argument. This causes the ext4 superblock mount
> code to subtract uninitialized pointers and pass the result to
> kmalloc, which results in very noisy failures.
>
> Per Ted's suggestion, initialize the args struct so that
> we know whether match_token() found an argument for the
> option, and skip match_int() if not.
>
> Also, return error (0) from parse_options if we thought
> we found an argument, but match_int() Fails.
>
> Reported-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
> Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
> Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
>
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 735c20d..68a55df 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -1229,6 +1229,11 @@ static int parse_options(char *options, struct super_block *sb,
> if (!*p)
> continue;
>
> + /*
> + * Initialize args struct so we know whether arg was
> + * found; some options take optional arguments.
> + */
> + args[0].to = args[0].from = 0;
> token = match_token(p, tokens, args);
> switch (token) {
> case Opt_bsd_df:
> @@ -1518,10 +1523,11 @@ set_qf_format:
> clear_opt(sbi->s_mount_opt, BARRIER);
> break;
> case Opt_barrier:
> - if (match_int(&args[0], &option)) {
> - set_opt(sbi->s_mount_opt, BARRIER);
> - break;
> - }
> + if (args[0].from) {
> + if (match_int(&args[0], &option))
> + return 0;
> + } else
> + option = 1; /* No argument, default to 1 */
> if (option)
> set_opt(sbi->s_mount_opt, BARRIER);
> else
> @@ -1594,10 +1600,11 @@ set_qf_format:
> set_opt(sbi->s_mount_opt,NO_AUTO_DA_ALLOC);
> break;
> case Opt_auto_da_alloc:
> - if (match_int(&args[0], &option)) {
> - clear_opt(sbi->s_mount_opt, NO_AUTO_DA_ALLOC);
> - break;
> - }
> + if (args[0].from) {
> + if (match_int(&args[0], &option))
> + return 0;
> + } else
> + option = 1; /* No argument, default to 1 */
> if (option)
> clear_opt(sbi->s_mount_opt, NO_AUTO_DA_ALLOC);
> else
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