linux-fsdevel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Jan Kara <jack@suse.cz>
To: Barret Rhoden <brho@google.com>
Cc: Dan Williams <dan.j.williams@intel.com>,
	linux-nvdimm@lists.01.org, hch@lst.de,
	linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, jack@suse.cz,
	ross.zwisler@linux.intel.com
Subject: Re: [PATCH v5 07/11] filesystem-dax: Introduce dax_lock_mapping_entry()
Date: Thu, 27 Sep 2018 13:13:54 +0200	[thread overview]
Message-ID: <20180927111354.GA16469@quack2.suse.cz> (raw)
In-Reply-To: <20180924115721.75893931@gnomeregan.cam.corp.google.com>

On Mon 24-09-18 11:57:21, Barret Rhoden wrote:
> Hi Dan -
> 
> On 2018-07-04 at 14:41 Dan Williams <dan.j.williams@intel.com> wrote:
> [snip]
> > diff --git a/fs/dax.c b/fs/dax.c
> > index 4de11ed463ce..57ec272038da 100644
> > --- a/fs/dax.c
> > +++ b/fs/dax.c
> [snip]
> > +bool dax_lock_mapping_entry(struct page *page)
> > +{
> > +	pgoff_t index;
> > +	struct inode *inode;
> > +	bool did_lock = false;
> > +	void *entry = NULL, **slot;
> > +	struct address_space *mapping;
> > +
> > +	rcu_read_lock();
> > +	for (;;) {
> > +		mapping = READ_ONCE(page->mapping);
> > +
> > +		if (!dax_mapping(mapping))
> > +			break;
> > +
> > +		/*
> > +		 * In the device-dax case there's no need to lock, a
> > +		 * struct dev_pagemap pin is sufficient to keep the
> > +		 * inode alive, and we assume we have dev_pagemap pin
> > +		 * otherwise we would not have a valid pfn_to_page()
> > +		 * translation.
> > +		 */
> > +		inode = mapping->host;
> > +		if (S_ISCHR(inode->i_mode)) {
> > +			did_lock = true;
> > +			break;
> > +		}
> > +
> > +		xa_lock_irq(&mapping->i_pages);
> > +		if (mapping != page->mapping) {
> > +			xa_unlock_irq(&mapping->i_pages);
> > +			continue;
> > +		}
> > +		index = page->index;
> > +
> > +		entry = __get_unlocked_mapping_entry(mapping, index, &slot,
> > +				entry_wait_revalidate);
> > +		if (!entry) {
> > +			xa_unlock_irq(&mapping->i_pages);
> > +			break;
> > +		} else if (IS_ERR(entry)) {
> > +			WARN_ON_ONCE(PTR_ERR(entry) != -EAGAIN);
> > +			continue;
> 
> In the IS_ERR case, do you need to xa_unlock the mapping?  It looks
> like you'll deadlock the next time around the loop.

Yep, that looks certainly wrong. I'll send a fix.

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

  reply	other threads:[~2018-09-27 11:13 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-04 21:40 [PATCH v5 00/11] mm: Teach memory_failure() about ZONE_DEVICE pages Dan Williams
2018-07-04 21:40 ` [PATCH v5 01/11] device-dax: Convert to vmf_insert_mixed and vm_fault_t Dan Williams
2018-07-04 21:40 ` [PATCH v5 02/11] device-dax: Enable page_mapping() Dan Williams
2018-07-04 21:40 ` [PATCH v5 03/11] device-dax: Set page->index Dan Williams
2018-07-04 21:40 ` [PATCH v5 04/11] filesystem-dax: " Dan Williams
2018-07-04 21:40 ` [PATCH v5 05/11] mm, madvise_inject_error: Let memory_failure() optionally take a page reference Dan Williams
2018-07-13  6:31   ` Naoya Horiguchi
2018-07-14  0:34     ` Dan Williams
2018-07-04 21:40 ` [PATCH v5 06/11] mm, memory_failure: Collect mapping size in collect_procs() Dan Williams
2018-07-13  6:49   ` Naoya Horiguchi
2018-07-04 21:41 ` [PATCH v5 07/11] filesystem-dax: Introduce dax_lock_mapping_entry() Dan Williams
2018-07-05  1:07   ` kbuild test robot
2018-07-05  3:31   ` kbuild test robot
2018-07-05  3:33   ` [PATCH v6] " Dan Williams
2018-09-24 15:57   ` [PATCH v5 07/11] " Barret Rhoden
2018-09-27 11:13     ` Jan Kara [this message]
2018-07-04 21:41 ` [PATCH v5 08/11] mm, memory_failure: Teach memory_failure() about dev_pagemap pages Dan Williams
2018-07-13  8:52   ` Naoya Horiguchi
2018-07-14  0:28     ` Dan Williams
2018-07-17  6:36       ` Naoya Horiguchi
2018-07-04 21:41 ` [PATCH v5 09/11] x86/mm/pat: Prepare {reserve, free}_memtype() for "decoy" addresses Dan Williams
2018-07-04 21:41 ` [PATCH v5 10/11] x86/memory_failure: Introduce {set, clear}_mce_nospec() Dan Williams
2018-07-04 21:41 ` [PATCH v5 11/11] libnvdimm, pmem: Restore page attributes when clearing errors Dan Williams
2018-07-13  4:44 ` [PATCH v5 00/11] mm: Teach memory_failure() about ZONE_DEVICE pages Dan Williams

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20180927111354.GA16469@quack2.suse.cz \
    --to=jack@suse.cz \
    --cc=brho@google.com \
    --cc=dan.j.williams@intel.com \
    --cc=hch@lst.de \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=linux-nvdimm@lists.01.org \
    --cc=ross.zwisler@linux.intel.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).