From: Nick Piggin <npiggin@kernel.dk>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: npiggin@kernel.dk, linux-kernel@vger.kernel.org,
linux-fsdevel@vger.kernel.org
Subject: Re: [patch 19/35] fs: icache remove redundant i_sb_list umount locking
Date: Thu, 21 Oct 2010 00:03:45 +1100 [thread overview]
Message-ID: <20101020130345.GA6663@amd> (raw)
In-Reply-To: <20101020124631.GA24394@ZenIV.linux.org.uk>
On Wed, Oct 20, 2010 at 01:46:31PM +0100, Al Viro wrote:
> On Tue, Oct 19, 2010 at 02:42:35PM +1100, npiggin@kernel.dk wrote:
> > + /*
> > + * We can walk the per-sb list of inodes here without worrying about
> > + * its consistency, because the list must not change during umount
> > + * anymore, and because iprune_sem keeps shrink_icache_memory() away.
> > + */
> > fsnotify_unmount_inodes(&sb->s_inodes);
>
> OK, explain to me why is that safe. Note that fsnotify_destroy_mark()
> _can_ race with umount, dropping the last reference to inode before
> fsnotify_unmount_inodes() would get to it and kill it (along with the mark).
> With the current code it's just fine - we walk the list under lock and
> iput() won't mess with that list until it acquires the damn lock. And
> no matter who gets there first, the mark will be destroyed and reference
> to inode will be dropped.
>
> With your change, AFAICS, removal from the list can happen while we walk
> it. With obvious results.
Ah, tricky. So after fsnotify_unmount_inodes runs, the invalidate_list
is now safe because no more marks can put the inode at that point? OK I
can concede that point and drop the patch, thanks.
Where can fsnotify_destroy_mark run concurrently at umount time, can you
explain? I haven't spotted it yet.
next prev parent reply other threads:[~2010-10-20 13:03 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-19 3:42 [patch 00/35] my inode scaling series for review npiggin
2010-10-19 3:42 ` [patch 01/35] bit_spinlock: add required includes npiggin
2010-10-19 3:42 ` [patch 02/35] kernel: add bl_list npiggin
2010-10-19 3:42 ` [patch 03/35] mm: implement per-zone shrinker npiggin
2010-10-19 4:49 ` KOSAKI Motohiro
2010-10-19 5:33 ` Nick Piggin
2010-10-19 5:40 ` KOSAKI Motohiro
2010-10-19 3:42 ` [patch 04/35] vfs: convert inode and dentry caches to " npiggin
2010-10-19 3:42 ` [patch 05/35] fs: icache lock s_inodes list npiggin
2010-10-19 3:42 ` [patch 06/35] fs: icache lock inode hash npiggin
2010-10-19 3:42 ` [patch 07/35] fs: icache lock i_state npiggin
2010-10-19 10:47 ` Miklos Szeredi
2010-10-19 17:06 ` Peter Zijlstra
2010-10-19 3:42 ` [patch 08/35] fs: icache lock i_count npiggin
2010-10-19 10:16 ` Boaz Harrosh
2010-10-20 2:14 ` Nick Piggin
2010-10-19 3:42 ` [patch 09/35] fs: icache lock lru/writeback lists npiggin
2010-10-19 3:42 ` [patch 10/35] fs: icache atomic inodes_stat npiggin
2010-10-19 3:42 ` [patch 11/35] fs: icache lock inode state npiggin
2010-10-19 3:42 ` [patch 12/35] fs: inode atomic last_ino, iunique lock npiggin
2010-10-19 3:42 ` [patch 13/35] fs: icache remove inode_lock npiggin
2010-10-19 3:42 ` [patch 14/35] fs: icache factor hash lock into functions npiggin
2010-10-19 3:42 ` [patch 15/35] fs: icache per-bucket inode hash locks npiggin
2010-10-19 3:42 ` [patch 16/35] fs: icache lazy inode lru npiggin
2010-10-19 3:42 ` [patch 17/35] fs: icache RCU free inodes npiggin
2010-10-19 3:42 ` [patch 18/35] fs: avoid inode RCU freeing for pseudo fs npiggin
2010-10-19 3:42 ` [patch 19/35] fs: icache remove redundant i_sb_list umount locking npiggin
2010-10-20 12:46 ` Al Viro
2010-10-20 13:03 ` Nick Piggin [this message]
2010-10-20 13:27 ` Al Viro
2010-10-19 3:42 ` [patch 20/35] fs: icache rcu walk for i_sb_list npiggin
2010-10-19 3:42 ` [patch 21/35] fs: icache per-cpu nr_inodes, non-atomic nr_unused counters npiggin
2010-10-19 3:42 ` [patch 22/35] fs: icache per-cpu last_ino allocator npiggin
2010-10-19 3:42 ` [patch 23/35] fs: icache use per-CPU lists and locks for sb inode lists npiggin
2010-10-19 15:33 ` Miklos Szeredi
2010-10-20 2:37 ` Nick Piggin
2010-10-19 3:42 ` [patch 24/35] fs: icache use RCU to avoid locking in hash lookups npiggin
2010-10-19 3:42 ` [patch 25/35] fs: icache reduce some locking overheads npiggin
2010-10-19 3:42 ` [patch 26/35] fs: icache alloc anonymous inode allocation npiggin
2010-10-19 15:50 ` Miklos Szeredi
2010-10-20 2:38 ` Nick Piggin
2010-10-19 16:33 ` Christoph Hellwig
2010-10-20 3:07 ` Nick Piggin
2010-10-19 3:42 ` [patch 27/35] fs: icache split IO and LRU lists npiggin
2010-10-19 16:12 ` Miklos Szeredi
2010-10-20 2:41 ` Nick Piggin
2010-10-19 3:42 ` [patch 28/35] fs: icache split writeback and lru locks npiggin
2010-10-19 3:42 ` [patch 29/35] fs: icache per-bdi writeback list locking npiggin
2010-10-19 3:42 ` [patch 30/35] fs: icache lazy LRU avoid LRU locking after IO operation npiggin
2010-10-19 3:42 ` [patch 31/35] fs: icache per-zone inode LRU npiggin
2010-10-19 12:38 ` Dave Chinner
2010-10-20 2:35 ` Nick Piggin
2010-10-20 3:12 ` Nick Piggin
2010-10-20 9:43 ` Dave Chinner
2010-10-20 10:02 ` Nick Piggin
2010-10-20 3:14 ` KOSAKI Motohiro
2010-10-20 3:20 ` Nick Piggin
2010-10-20 3:29 ` KOSAKI Motohiro
2010-10-20 10:19 ` Dave Chinner
2010-10-20 10:41 ` Nick Piggin
2010-10-19 3:42 ` [patch 32/35] fs: icache minimise I_FREEING latency npiggin
2010-10-19 3:42 ` [patch 33/35] fs: icache introduce inode_get/inode_get_ilock npiggin
2010-10-19 10:17 ` Boaz Harrosh
2010-10-20 2:17 ` Nick Piggin
2010-10-19 3:42 ` [patch 34/35] fs: inode rename i_count to i_refs npiggin
2010-10-19 3:42 ` [patch 35/35] fs: icache document more lock orders npiggin
2010-10-19 16:22 ` [patch 00/35] my inode scaling series for review Christoph Hellwig
2010-10-20 3:05 ` Nick Piggin
2010-10-20 13:14 ` Al Viro
2010-10-20 13:59 ` Nick Piggin
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