Re: 2.6.11-rc3-bk5: XFS: fcron: could not write() buf to disk: Resource temporarily unavailable

[Darren Williams <dsw@gelato.unsw.edu.au>]

Hi Nathan

I can also confirm that this patch resolves an issue I am seeing
with re-aim-7 writing to xfs fs mounted on ramdisk, I was also
getting EAGAIN.

Thanks
Darren

On Thu, 10 Feb 2005, Nathan Scott wrote:

> On Wed, Feb 09, 2005 at 05:44:54PM +0300, Alexander Y. Fomichev wrote:
> > On Wednesday 09 February 2005 04:29, Nathan Scott wrote:
> > > Is that an O_SYNC write, do you know?  Or a write to an inode
> > > with the sync flag set?
> > 
> > Yes, it is O_SYNC, as i can see from fcron sources, and, no, kernel
> 
> OK, thanks.
> 
> > > I'm chasing down a problem similar to this atm, so far looks like
> > > something in the generic VM code below sync_page_range is giving
> > > back EAGAIN, and that is getting passed back out to userspace by
> > > XFS.  Not sure where/why/how its been caused yet though ... I'll
> > > let you know once I have a fix or have found the culprit change.
> 
> Turns out it was actually XFS giving back this EAGAIN, indirectly -
> and some of the generic VM routines have been tweaked recently to
> propogate more sync write errors out to userspace.  Try this patch,
> it will fix your problem - we're still discussing if this is the
> ideal fix, so something else may be merged in the end.
> 
> cheers.
> 
> -- 
> Nathan
> 
> 
> Index: test/fs/xfs/linux-2.6/xfs_super.c
> ===================================================================
> --- test.orig/fs/xfs/linux-2.6/xfs_super.c
> +++ test/fs/xfs/linux-2.6/xfs_super.c
> @@ -348,6 +348,12 @@
>  		if (sync)
>  			flags |= FLUSH_SYNC;
>  		VOP_IFLUSH(vp, flags, error);
> +		if (error == EAGAIN) {
> +			if (sync)
> +				VOP_IFLUSH(vp, flags | FLUSH_LOG, error);
> +			else
> +				error = 0;
> +		}
>  	}
>  
>  	return -error;
> Index: test/fs/xfs/xfs_vnodeops.c
> ===================================================================
> --- test.orig/fs/xfs/xfs_vnodeops.c
> +++ test/fs/xfs/xfs_vnodeops.c
> @@ -3681,27 +3681,27 @@
>  {
>  	xfs_inode_t	*ip;
>  	xfs_mount_t	*mp;
> +	xfs_inode_log_item_t *iip;
>  	int		error = 0;
>  
>  	ip = XFS_BHVTOI(bdp);
>  	mp = ip->i_mount;
> +	iip = ip->i_itemp;
>  
>  	if (XFS_FORCED_SHUTDOWN(mp))
>  		return XFS_ERROR(EIO);
>  
> -	/* Bypass inodes which have already been cleaned by
> +	/*
> +	 * Bypass inodes which have already been cleaned by
>  	 * the inode flush clustering code inside xfs_iflush
>  	 */
>  	if ((ip->i_update_core == 0) &&
> -	    ((ip->i_itemp == NULL) ||
> -	     !(ip->i_itemp->ili_format.ilf_fields & XFS_ILOG_ALL)))
> +	    ((iip == NULL) || !(iip->ili_format.ilf_fields & XFS_ILOG_ALL)))
>  		return 0;
>  
>  	if (flags & FLUSH_LOG) {
> -		xfs_inode_log_item_t *iip = ip->i_itemp;
> -
>  		if (iip && iip->ili_last_lsn) {
> -			xlog_t	*log = mp->m_log;
> +			xlog_t		*log = mp->m_log;
>  			xfs_lsn_t	sync_lsn;
>  			int		s, log_flags = XFS_LOG_FORCE;
>  
> @@ -3714,12 +3714,14 @@
>  
>  			if (flags & FLUSH_SYNC)
>  				log_flags |= XFS_LOG_SYNC;
> -			return xfs_log_force(mp, iip->ili_last_lsn,
> -						log_flags);
> +			error = xfs_log_force(mp, iip->ili_last_lsn, log_flags);
> +			if (error)
> +				return error;
>  		}
>  	}
>  
> -	/* We make this non-blocking if the inode is contended,
> +	/*
> +	 * We make this non-blocking if the inode is contended,
>  	 * return EAGAIN to indicate to the caller that they
>  	 * did not succeed. This prevents the flush path from
>  	 * blocking on inodes inside another operation right
> @@ -3728,8 +3730,11 @@
>  	if (flags & FLUSH_INODE) {
>  		int	flush_flags;
>  
> +		if (!(flags & FLUSH_LOG))
> +			error = EAGAIN;
> +
>  		if (xfs_ipincount(ip))
> -			return EAGAIN;
> +			return error;
>  
>  		if (flags & FLUSH_SYNC) {
>  			xfs_ilock(ip, XFS_ILOCK_SHARED);
> @@ -3737,10 +3742,10 @@
>  		} else if (xfs_ilock_nowait(ip, XFS_ILOCK_SHARED)) {
>  			if (xfs_ipincount(ip) || !xfs_iflock_nowait(ip)) {
>  				xfs_iunlock(ip, XFS_ILOCK_SHARED);
> -				return EAGAIN;
> +				return error;
>  			}
>  		} else {
> -			return EAGAIN;
> +			return error;
>  		}
>  
>  		if (flags & FLUSH_SYNC)
> Index: test/fs/xfs/linux-2.6/xfs_lrw.c
> ===================================================================
> --- test.orig/fs/xfs/linux-2.6/xfs_lrw.c
> +++ test/fs/xfs/linux-2.6/xfs_lrw.c
> @@ -962,9 +962,9 @@
>  				xfs_trans_set_sync(tp);
>  				error = xfs_trans_commit(tp, 0, NULL);
>  				xfs_iunlock(xip, XFS_ILOCK_EXCL);
> -				if (error)
> -					goto out_unlock_internal;
>  			}
> +			if (error)
> +				goto out_unlock_internal;
>  		}
>  	
>  		xfs_rwunlock(bdp, locktype);
> -
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--------------------------------------------------
Darren Williams <dsw AT gelato.unsw.edu.au>
Gelato@UNSW <www.gelato.unsw.edu.au>
--------------------------------------------------