Re: [PATCH] Prevent log tail pushing from blocking on buffer locks

[Lachlan McIlroy <lachlan@sgi.com>]

Christoph Hellwig wrote:
> On Tue, Jul 22, 2008 at 04:32:27PM +1000, Lachlan McIlroy wrote:
>> This changes xfs_inode_item_push() to use XFS_IFLUSH_ASYNC_NOBLOCK when
>> flushing an inode so the flush wont block on inode cluster buffer lock.
>> Also change the prototype of the IOP_PUSH operation so that xfsaild_push()
>> can bump it's stuck count.
>>
>> This change was prompted by a deadlock that would only occur on a debug
>> XFS where a thread creating an inode had the buffer locked and was trying
>> to allocate space for the inode tracing facility.  That recursed back into
>> the filesystem to flush data which created a transaction and needed log
>> space which wasn't available.
> 
> The stuck propagation looks good, but I don't think this should be
> blindly done for all errors.  The only error where it makes sense is
> the EAGAIN from xfs_iflush.  All other returns inside the item_push
> handlers basically indicate filesystem corruption.

Good point.  Regardless of the error it's still an item that could not
be pushed and is effectively 'stuck'.  What do you recommend I do for
other errors?  Shutdown the filesystem?