linux-kernel - [GIT PULL] filesystem-dax fix for 4.19-rc6

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Date:   Sun, 30 Sep 2018 02:16:57 +0000
From:   "Williams, Dan J" <dan.j.williams@...el.com>
To:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>
Subject: [GIT PULL] filesystem-dax fix for 4.19-rc6

Hi Greg, please pull from...

  git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm tags/libnvdimm-fixes2-4.19-rc6

...to receive one more urgent fix for 4.19-rc6.

---

The following changes since commit 6bf4ca7fbc85d80446ac01c0d1d77db4d91a6d84:

  Linux 4.19-rc5 (2018-09-23 19:15:18 +0200)

are available in the Git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm tags/libnvdimm-fixes2-4.19-rc6

for you to fetch changes up to f52afc93cd018fe6910133a05d44671192d1aeb0:

  dax: Fix deadlock in dax_lock_mapping_entry() (2018-09-27 10:56:15 -0700)

----------------------------------------------------------------
filesystem-dax for 4.19-rc6

Fix a deadlock in the new for 4.19 dax_lock_mapping_entry() routine.

----------------------------------------------------------------
Jan Kara (1):
      dax: Fix deadlock in dax_lock_mapping_entry()

 fs/dax.c | 1 +
 1 file changed, 1 insertion(+)

commit f52afc93cd018fe6910133a05d44671192d1aeb0
Author: Jan Kara <jack@...e.cz>
Date:   Thu Sep 27 13:23:32 2018 +0200

    dax: Fix deadlock in dax_lock_mapping_entry()
    
    When dax_lock_mapping_entry() has to sleep to obtain entry lock, it will
    fail to unlock mapping->i_pages spinlock and thus immediately deadlock
    against itself when retrying to grab the entry lock again. Fix the
    problem by unlocking mapping->i_pages before retrying.
    
    Fixes: c2a7d2a11552 ("filesystem-dax: Introduce dax_lock_mapping_entry()")
    Reported-by: Barret Rhoden <brho@...gle.com>
    Signed-off-by: Jan Kara <jack@...e.cz>
    Signed-off-by: Dan Williams <dan.j.williams@...el.com>

diff --git a/fs/dax.c b/fs/dax.c
index f32d7125ad0f..e4ef8af31aa6 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -447,6 +447,7 @@ bool dax_lock_mapping_entry(struct page *page)
                        xa_unlock_irq(&mapping->i_pages);
                        break;
                } else if (IS_ERR(entry)) {
+                       xa_unlock_irq(&mapping->i_pages);
                        WARN_ON_ONCE(PTR_ERR(entry) != -EAGAIN);
                        continue;
                }