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From: Al Viro <viro@ZenIV.linux.org.uk>
To: NeilBrown <neilb@suse.de>
Cc: linux-mm@kvack.org, linux-nfs@vger.kernel.org,
	linux-kernel@vger.kernel.org, xfs@oss.sgi.com
Subject: Re: [PATCH 17/19] VFS: set PF_FSTRANS while namespace_sem is held.
Date: Wed, 16 Apr 2014 05:46:18 +0100	[thread overview]
Message-ID: <20140416044618.GX18016@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20140416040337.10604.86740.stgit@notabene.brown>

On Wed, Apr 16, 2014 at 02:03:37PM +1000, NeilBrown wrote:
> namespace_sem can be taken while various i_mutex locks are held, so we
> need to avoid reclaim from blocking on an FS (particularly loop-back
> NFS).

I would really prefer to deal with that differently - by explicit change of
gfp_t arguments of allocators.

The thing is, namespace_sem is held *only* over allocations, and not a lot
of them, at that - only mnt_alloc_id(), mnt_alloc_group_id(), alloc_vfsmnt()
and new_mountpoint().  That is all that is allowed.

Again, actual work with filesystems (setup, shutdown, remount, pathname
resolution, etc.) is all done outside of namespace_sem; it's held only
for manipulations of fs/{namespace,pnode}.c data structures and the only
reason it isn't a spinlock is that we need to do some allocations.

So I'd rather slap GFP_NOFS on those few allocations...

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  reply	other threads:[~2014-04-16  4:46 UTC|newest]

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-04-16  4:03 [PATCH/RFC 00/19] Support loop-back NFS mounts NeilBrown
2014-04-16  4:03 ` [PATCH 10/19] NET: set PF_FSTRANS while holding sk_lock NeilBrown
2014-04-16  5:13   ` Eric Dumazet
2014-04-16  5:47     ` NeilBrown
2014-04-16 13:00     ` David Miller
2014-04-17  2:38       ` NeilBrown
2014-04-16  4:03 ` [PATCH 11/19] FS: set PF_FSTRANS while holding mmap_sem in exec.c NeilBrown
2014-04-16  4:03 ` [PATCH 14/19] driver core: set PF_FSTRANS while holding gdp_mutex NeilBrown
2014-04-16  4:03 ` [PATCH 07/19] nfsd and VM: use PF_LESS_THROTTLE to avoid throttle in shrink_inactive_list NeilBrown
2014-04-16  4:03 ` [PATCH 09/19] XFS: ensure xfs_file_*_read cannot deadlock in memory allocation NeilBrown
2014-04-16  6:04   ` Dave Chinner
2014-04-16  6:27     ` NeilBrown
2014-04-16  6:31     ` Dave Chinner
2014-04-16  4:03 ` [PATCH 02/19] lockdep: lockdep_set_current_reclaim_state should save old value NeilBrown
2014-04-16  4:03 ` [PATCH 13/19] MM: set PF_FSTRANS while allocating per-cpu memory to avoid deadlock NeilBrown
2014-04-16  5:49   ` Dave Chinner
2014-04-16  6:22     ` NeilBrown
2014-04-16  6:30       ` Dave Chinner
2014-04-16  4:03 ` [PATCH 08/19] Set PF_FSTRANS while write_cache_pages calls ->writepage NeilBrown
2014-04-16  4:03 ` [PATCH 06/19] nfsd: set PF_FSTRANS for nfsd threads NeilBrown
2014-04-16  7:28   ` Peter Zijlstra
2014-04-16  4:03 ` [PATCH 03/19] lockdep: improve scenario messages for RECLAIM_FS errors NeilBrown
2014-04-16  7:22   ` Peter Zijlstra
2014-04-16  4:03 ` [PATCH 05/19] SUNRPC: track whether a request is coming from a loop-back interface NeilBrown
2014-04-16 14:47   ` Jeff Layton
2014-04-16 23:25     ` NeilBrown
2014-04-16  4:03 ` [PATCH 04/19] Make effect of PF_FSTRANS to disable __GFP_FS universal NeilBrown
2014-04-16  5:37   ` Dave Chinner
2014-04-16  6:17     ` NeilBrown
2014-04-17  1:03       ` NeilBrown
2014-04-17  4:41         ` Dave Chinner
2014-04-16  4:03 ` [PATCH 01/19] Promote current_{set, restore}_flags_nested from xfs to global NeilBrown
2014-04-16  4:03 ` [PATCH 12/19] NET: set PF_FSTRANS while holding rtnl_lock NeilBrown
2014-04-16  4:03 ` [PATCH 18/19] nfsd: set PF_FSTRANS during nfsd4_do_callback_rpc NeilBrown
2014-04-16  4:03 ` [PATCH 15/19] nfsd: set PF_FSTRANS when client_mutex is held NeilBrown
2014-04-16  4:03 ` [PATCH 17/19] VFS: set PF_FSTRANS while namespace_sem " NeilBrown
2014-04-16  4:46   ` Al Viro [this message]
2014-04-16  5:52     ` NeilBrown
     [not found]       ` <20140416155230.4d02e4b9-wvvUuzkyo1EYVZTmpyfIwg@public.gmane.org>
2014-04-16 16:37         ` Al Viro
2014-04-16  4:03 ` [PATCH 19/19] XFS: set PF_FSTRANS while ilock is held in xfs_free_eofblocks NeilBrown
2014-04-16  6:18   ` Dave Chinner
2014-04-16  4:03 ` [PATCH 16/19] VFS: use GFP_NOFS rather than GFP_KERNEL in __d_alloc NeilBrown
2014-04-16  6:25   ` Dave Chinner
2014-04-16  6:49     ` NeilBrown
2014-04-16  9:00       ` Dave Chinner
2014-04-17  0:51         ` NeilBrown
2014-04-17  5:58           ` Dave Chinner
2014-04-16 14:42 ` [PATCH/RFC 00/19] Support loop-back NFS mounts Jeff Layton
2014-04-17  0:20   ` NeilBrown
2014-04-17  1:27     ` Dave Chinner
2014-04-17  1:50       ` NeilBrown
2014-04-17  4:23         ` Dave Chinner

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