lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:   Tue, 4 Apr 2017 10:09:09 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Jeff Layton <jlayton@...hat.com>
Cc:     NeilBrown <neilb@...e.com>, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-ext4@...r.kernel.org,
        akpm@...ux-foundation.org, tytso@....edu, jack@...e.cz
Subject: Re: [RFC PATCH 0/4] fs: introduce new writeback error tracking
 infrastructure and convert ext4 to use it

On Tue, Apr 04, 2017 at 12:25:46PM -0400, Jeff Layton wrote:
> That said, I think giving more specific errors where we can is useful.
> When your program is erroring out and writing 'I/O error' to the logs,
> then how much time will your admins burn before they figure out that it
> really failed because the filesystem was full?

df is one of the first things I check ... a few years ago, I also learned
to check df -i ... ;-)

Anyway, given the decision to simply report the last error lets us do this
implementation:

void filemap_set_wb_error(struct address_space *mapping, int err)
{
	struct inode *inode = mapping->host;
	unsigned int wb_err;

	if (!err)
		return;
	/*
	 * This should be called with the error code that we want to return
	 * on fsync. Thus, it should always be <= 0.
	 */
	WARN_ON(err > 0 || err < -MAX_ERRNO);

	spin_lock(&inode->i_lock);
	wb_err = ((mapping->wb_err & ~MAX_ERRNO) + (1 << 12)) | -err;
	WRITE_ONCE(mapping->wb_err, wb_err);
	spin_unlock(&inode->i_lock);
}

int filemap_report_wb_error(struct file *file)
{
	struct inode *inode = file_inode(file);
	unsigned int wb_err = READ_ONCE(mapping->wb_err);

	if (file->f_wb_err == wb_err)
		return 0;
	return -(wb_err & 4095);
}

That only gives us 20 bits of counter, but I think that's enough.

Powered by blists - more mailing lists