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Re: [PATCH 24/25] r/o bind mounts: track number of mount writers

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From: Dave Hansen <haveblue@...>
To: Christoph Hellwig <hch@...>
Cc: <akpm@...>, <linux-kernel@...>
Subject: Re: [PATCH 24/25] r/o bind mounts: track number of mount writers
Date: Monday, September 24, 2007 - 3:28 pm

On Mon, 2007-09-24 at 18:54 +0100, Christoph Hellwig wrote:

I'll take a look at xfs to see what I can get out of it.

There are basically two times when you have to do this
for_each_possible_cpu() stuff:
1. when doing a r/w->r/o transition, which is rare, and
   certainly not a fast path
2. Where the per-cpu writer count underflows.  This requires
   a _minimum_ of 1<<16 file opens (configurable) each of which
   is closed on a different cpu than it was opened on.  Even
   if you were trying, I'm not sure you'd notice the overhead.

-- Dave

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Messages in current thread:
[PATCH 00/25] Read-only bind mounts, Dave Hansen, (Thu Sep 20, 3:52 pm)
[PATCH 24/25] r/o bind mounts: track number of mount writers, Dave Hansen, (Thu Sep 20, 3:53 pm)
Re: [PATCH 24/25] r/o bind mounts: track number of mount wri..., Christoph Hellwig, (Mon Sep 24, 1:54 pm)
Re: [PATCH 24/25] r/o bind mounts: track number of mount wri..., Dave Hansen, (Mon Sep 24, 3:28 pm)
Re: [PATCH 24/25] r/o bind mounts: track number of mount wri..., Andrew Morton, (Mon Sep 24, 3:42 pm)
Re: [PATCH 24/25] r/o bind mounts: track number of mount wri..., Dave Hansen, (Mon Oct 1, 2:06 pm)
Re: [PATCH 24/25] r/o bind mounts: track number of mount wri..., Andrew Morton, (Mon Sep 24, 3:10 pm)
Re: [PATCH 24/25] r/o bind mounts: track number of mount wri..., Christoph Hellwig, (Mon Sep 24, 3:24 pm)
Re: [PATCH 24/25] r/o bind mounts: track number of mount wri..., Andrew Morton, (Mon Sep 24, 2:17 am)
Re: [PATCH 24/25] r/o bind mounts: track number of mount wri..., Dave Hansen, (Mon Sep 24, 6:06 pm)
Re: [PATCH 24/25] r/o bind mounts: track number of mount wri..., Andrew Morton, (Mon Sep 24, 6:25 pm)
Re: [PATCH 24/25] r/o bind mounts: track number of mount wri..., Dave Hansen, (Mon Sep 24, 7:05 pm)
Re: [PATCH 24/25] r/o bind mounts: track number of mount wri..., Andrew Morton, (Mon Sep 24, 7:15 pm)
Re: [PATCH 24/25] r/o bind mounts: track number of mount wri..., Dave Hansen, (Tue Sep 25, 12:10 pm)
Re: [PATCH 24/25] r/o bind mounts: track number of mount wri..., Arjan van de Ven, (Mon Sep 24, 10:34 am)
[PATCH 25/25] honor r/w changes at do_remount() time, Dave Hansen, (Thu Sep 20, 3:53 pm)
[PATCH 23/25] do_rmdir(): elevate write count, Dave Hansen, (Thu Sep 20, 3:53 pm)
[PATCH 22/25] elevate mnt writers for vfs_unlink() callers, Dave Hansen, (Thu Sep 20, 3:53 pm)
[PATCH 21/25] sys_mknodat(): elevate write count for vfs_mkn..., Dave Hansen, (Thu Sep 20, 3:53 pm)
[PATCH 13/25] elevate mount count for extended attributes, Dave Hansen, (Thu Sep 20, 3:53 pm)
[PATCH 06/25] elevate write count open()'d files, Dave Hansen, (Thu Sep 20, 3:52 pm)
Re: [PATCH 06/25] elevate write count open()'d files, Andrew Morton, (Wed Nov 28, 4:41 am)
Re: [PATCH 06/25] elevate write count open()'d files, Dave Hansen, (Wed Nov 28, 1:33 pm)
[PATCH 20/25] elevate write count for do_sys_utime() and tou..., Dave Hansen, (Thu Sep 20, 3:53 pm)
[PATCH 19/25] elevate write count for do_utimes(), Dave Hansen, (Thu Sep 20, 3:53 pm)
[PATCH 18/25] elevate writer count for do_sys_truncate(), Dave Hansen, (Thu Sep 20, 3:53 pm)
[PATCH 14/25] elevate write count for file_update_time(), Dave Hansen, (Thu Sep 20, 3:53 pm)
[PATCH 17/25] nfs: check mnt instead of superblock directly, Dave Hansen, (Thu Sep 20, 3:53 pm)
[PATCH 02/25] rearrange may_open() to be r/o friendly, Dave Hansen, (Thu Sep 20, 3:52 pm)
[PATCH 16/25] elevate write count over calls to vfs_rename(), Dave Hansen, (Thu Sep 20, 3:53 pm)
[PATCH 15/25] unix_find_other() elevate write count for touc..., Dave Hansen, (Thu Sep 20, 3:53 pm)
[PATCH 10/25] elevate mnt writers for callers of vfs_mkdir(), Dave Hansen, (Thu Sep 20, 3:53 pm)
[PATCH 07/25] r/o bind mounts: elevate write count for some ..., Dave Hansen, (Thu Sep 20, 3:52 pm)
Re: [PATCH 07/25] r/o bind mounts: elevate write count for s..., Andrew Morton, (Fri Sep 21, 7:03 pm)
Re: [PATCH 07/25] r/o bind mounts: elevate write count for s..., Dave Hansen, (Fri Sep 21, 7:39 pm)
Re: [PATCH 07/25] r/o bind mounts: elevate write count for s..., Andrew Morton, (Fri Sep 21, 7:47 pm)
Re: [PATCH 07/25] r/o bind mounts: elevate write count for s..., Andrew Morton, (Fri Sep 21, 4:17 am)
[RFC] detect missed mnt_want_write() calls, Dave Hansen, (Tue Sep 25, 9:34 pm)
Re: [PATCH 07/25] r/o bind mounts: elevate write count for s..., Dave Hansen, (Fri Sep 21, 5:15 pm)
[PATCH 08/25] elevate writer count for chown and friends, Dave Hansen, (Thu Sep 20, 3:52 pm)
[PATCH 12/25] elevate write count for link and symlink calls, Dave Hansen, (Thu Sep 20, 3:53 pm)
[PATCH 11/25] elevate write count during entire ncp_ioctl(), Dave Hansen, (Thu Sep 20, 3:53 pm)
[PATCH 09/25] make access() use mnt check, Dave Hansen, (Thu Sep 20, 3:53 pm)
[PATCH 05/25] r/o bind mounts: stub functions, Dave Hansen, (Thu Sep 20, 3:52 pm)
[PATCH 04/25] create cleanup helper svc_msnfs(), Dave Hansen, (Thu Sep 20, 3:52 pm)
[PATCH 03/25] give may_open() a local 'mnt' variable, Dave Hansen, (Thu Sep 20, 3:52 pm)
Re: [PATCH 03/25] give may_open() a local 'mnt' variable, Christoph Hellwig, (Thu Sep 20, 3:57 pm)
[PATCH 01/25] filesystem helpers for custom 'struct file's, Dave Hansen, (Thu Sep 20, 3:52 pm)