fs: fix hang with BSD accounting on frozen filesystem

When BSD process accounting is enabled and logs information to a
filesystem which gets frozen, system easily becomes unusable because each
attempt to account process information blocks.  Thus e.g.  every task gets
blocked in exit.

It seems better to drop accounting information (which can already happen
when filesystem is running out of space) instead of locking system up.  So
we open the accounting file with O_NONBLOCK.

Signed-off-by: Jan Kara <jack@suse.cz>
Reported-by: Nikola Ciprich <nikola.ciprich@linuxbox.cz>
Tested-by: Nikola Ciprich <nikola.ciprich@linuxbox.cz>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Marco Stornelli <marco.stornelli@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/kernel/acct.c b/kernel/acct.c
index 85389fe2abd0a95bf99d4abe6b1de63e09351c4c..b714d76288b91099796ad4e82b408d971e30ecbc 100644 (file)
--- a/kernel/acct.c
+++ b/kernel/acct.c
@@ -201,7 +201,8 @@ static int acct_on(struct filename *pathname)
        struct bsd_acct_struct *acct = NULL;
 
        /* Difference from BSD - they don't do O_APPEND */
-       file = file_open_name(pathname, O_WRONLY|O_APPEND|O_LARGEFILE, 0);
+       file = file_open_name(pathname,
+                             O_WRONLY|O_APPEND|O_LARGEFILE|O_NONBLOCK, 0);
        if (IS_ERR(file))
                return PTR_ERR(file);