Re: [Patch] Catch filesystems lacking s_bdi

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From: Jens Axboe

Subject: Re: [Patch] Catch filesystems lacking s_bdi

Date: Monday, April 26, 2010 - 7:38 am

On Mon, Apr 26 2010, Jörn Engel wrote:
quoted text> > Yeah, it's a bad situation to be in. I changed that BUG_ON() to a
> > WARN_ON(). I'm not too worried about that part, I'm more worried about
> > the file system changed. OTOH, they do lack proper flushing now, so it's
> > likely not a huge risk from that perspective.
> 
> It is worse still.  Using mtd->backing_dev_info results in 
> kernel BUG at fs/fs-writeback.c:157
> 
> which is BUG_ON(!work->seen); in bdi_queue_work().  Logfs is affected
> and I bet jffs2 is as well.  So much for dwmw2 or me actually testing
> the fix. :(
> 
> I did a hexdump to see what sb->s_bdi actually contained and the result
> was this:
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 04 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> 00 00 00 00 00 00 00 00                          ........
> 
> Which should be mtd_bdi_unmappable.  And at this point I have to admit
> being clueless.  What exactly should a struct backing_dev_info contain
> and for what purposes?  And where is this documented?

The important bit is that each bdi must be initialized and registered if
it's going to be handling dirty data, it can't just be a static
placeholder. See the bdi_setup_and_register() helper I added.

-- 
Jens Axboe

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Messages in current thread:

[PATCH] [MTD] Fix JFFS2 sync silent failure, Jörn Engel, (Sat Apr 17, 11:40 am)

Re: [PATCH] [MTD] Fix JFFS2 sync silent failure, Jens Axboe, (Mon Apr 19, 12:38 am)

Re: [PATCH] [MTD] Fix JFFS2 sync silent failure, Jörn Engel, (Mon Apr 19, 3:15 am)

Re: [PATCH] [MTD] Fix JFFS2 sync silent failure, Jens Axboe, (Mon Apr 19, 3:20 am)

Re: [PATCH] [MTD] Fix JFFS2 sync silent failure, Jörn Engel, (Mon Apr 19, 4:39 am)

Re: [PATCH] [MTD] Fix JFFS2 sync silent failure, Jörn Engel, (Wed Apr 21, 10:54 pm)

Re: [PATCH] [MTD] Fix JFFS2 sync silent failure, Jörn Engel, (Wed Apr 21, 11:26 pm)

Re: [PATCH] [MTD] Fix JFFS2 sync silent failure, Jens Axboe, (Thu Apr 22, 2:03 am)

Re: [PATCH] [MTD] Fix JFFS2 sync silent failure, Jens Axboe, (Thu Apr 22, 3:39 am)

Re: [PATCH] [MTD] Fix JFFS2 sync silent failure, David Woodhouse, (Thu Apr 22, 3:58 am)

Re: [PATCH] [MTD] Fix JFFS2 sync silent failure, Jens Axboe, (Thu Apr 22, 4:05 am)

Re: [PATCH] [MTD] Fix JFFS2 sync silent failure, Jörn Engel, (Thu Apr 22, 4:55 am)

Re: [PATCH] [MTD] Fix JFFS2 sync silent failure, Jens Axboe, (Thu Apr 22, 5:08 am)

Re: [PATCH] [MTD] Fix JFFS2 sync silent failure, Jörn Engel, (Thu Apr 22, 5:17 am)

Re: [PATCH] [MTD] Fix JFFS2 sync silent failure, Linus Torvalds, (Thu Apr 22, 7:25 am)

Re: [PATCH] [MTD] Fix JFFS2 sync silent failure, Linus Torvalds, (Thu Apr 22, 7:33 am)

Re: [PATCH] [MTD] Fix JFFS2 sync silent failure, Jens Axboe, (Thu Apr 22, 9:27 am)

[Patch] Catch filesystems lacking s_bdi, Jörn Engel, (Thu Apr 22, 1:33 pm)

Re: [Patch] Catch filesystems lacking s_bdi, Jens Axboe, (Fri Apr 23, 3:05 am)

Re: [Patch] Catch filesystems lacking s_bdi, Jörn Engel, (Fri Apr 23, 1:55 pm)

Re: [Patch] Catch filesystems lacking s_bdi, Jens Axboe, (Mon Apr 26, 2:48 am)

Re: [Patch] Catch filesystems lacking s_bdi, Jörn Engel, (Mon Apr 26, 7:32 am)

Re: [Patch] Catch filesystems lacking s_bdi, Jens Axboe, (Mon Apr 26, 7:38 am)

Re: [Patch] Catch filesystems lacking s_bdi, Jens Axboe, (Mon Apr 26, 7:45 am)

[PATCH 1/2] [MTD] Move mtd_bdi_*mappable to mtdcore.c, Jörn Engel, (Mon Apr 26, 9:30 am)

[PATCH 2/2] [MTD] Call bdi_init() and bdi_register(), Jörn Engel, (Mon Apr 26, 9:31 am)

Re: [PATCH 1/2] [MTD] Move mtd_bdi_*mappable to mtdcore.c, Jens Axboe, (Mon Apr 26, 10:01 am)

Re: [PATCH 2/2] [MTD] Call bdi_init() and bdi_register(), Jens Axboe, (Mon Apr 26, 10:02 am)

Re: [PATCH 1/2] [MTD] Move mtd_bdi_*mappable to mtdcore.c, Jörn Engel, (Mon Apr 26, 10:08 am)

Re: [PATCH 1/2] [MTD] Move mtd_bdi_*mappable to mtdcore.c, Jens Axboe, (Mon Apr 26, 10:10 am)

Re: [PATCH 2/2] [MTD] Call bdi_init() and bdi_register(), Jörn Engel, (Mon Apr 26, 10:12 am)

Re: [PATCH 2/2] [MTD] Call bdi_init() and bdi_register(), Jens Axboe, (Tue Apr 27, 12:52 am)

Re: [PATCH 2/2] [MTD] Call bdi_init() and bdi_register(), Paolo Minazzi, (Tue Apr 27, 1:11 am)

Re: [PATCH 2/2] [MTD] Call bdi_init() and bdi_register(), Jens Axboe, (Tue Apr 27, 1:16 am)

Re: [PATCH 2/2] [MTD] Call bdi_init() and bdi_register(), Paolo Minazzi, (Tue Apr 27, 2:01 am)

Re: [PATCH 2/2] [MTD] Call bdi_init() and bdi_register(), Jens Axboe, (Tue Apr 27, 2:16 am)

Re: [PATCH 2/2] [MTD] Call bdi_init() and bdi_register(), Paolo Minazzi, (Tue Apr 27, 2:26 am)

Re: [PATCH 2/2] [MTD] Call bdi_init() and bdi_register(), Jens Axboe, (Tue Apr 27, 2:29 am)

Re: [PATCH 2/2] [MTD] Call bdi_init() and bdi_register(), Paolo Minazzi, (Tue Apr 27, 2:36 am)

Re: [PATCH 2/2] [MTD] Call bdi_init() and bdi_register(), Jörn Engel, (Tue Apr 27, 4:17 am)

Re: [PATCH 2/2] [MTD] Call bdi_init() and bdi_register(), Jörn Engel, (Tue Apr 27, 4:29 am)

Re: [PATCH 2/2] [MTD] Call bdi_init() and bdi_register(), Paolo Minazzi, (Tue Apr 27, 4:31 am)

Re: [PATCH 2/2] [MTD] Call bdi_init() and bdi_register(), Jens Axboe, (Tue Apr 27, 4:33 am)

Re: [PATCH 2/2] [MTD] Call bdi_init() and bdi_register(), Jörn Engel, (Tue Apr 27, 4:40 am)

[PATCH] [LogFS] Return -EINVAL if filesystem image doesn't ..., Jörn Engel, (Tue Apr 27, 4:48 am)

Re: [PATCH 2/2] [MTD] Call bdi_init() and bdi_register(), Paolo Minazzi, (Tue Apr 27, 4:54 am)

Re: [PATCH 2/2] [MTD] Call bdi_init() and bdi_register(), Jörn Engel, (Tue Apr 27, 5:05 am)

Re: [PATCH] [LogFS] Return -EINVAL if filesystem image doe ..., Paolo Minazzi, (Tue Apr 27, 5:53 am)

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