From: Ira Weiny <ira.weiny@intel.com> To: "Darrick J. Wong" <darrick.wong@oracle.com> Cc: linux-kernel@vger.kernel.org, Alexander Viro <viro@zeniv.linux.org.uk>, Dan Williams <dan.j.williams@intel.com>, Dave Chinner <david@fromorbit.com>, Christoph Hellwig <hch@lst.de>, "Theodore Y. Ts'o" <tytso@mit.edu>, Jan Kara <jack@suse.cz>, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [RFC PATCH V2 08/12] fs/xfs: Add lock/unlock mode to xfs Date: Tue, 14 Jan 2020 16:57:28 -0800 Message-ID: <20200115005727.GB23311@iweiny-DESK2.sc.intel.com> (raw) In-Reply-To: <20200114003521.GB29860@iweiny-DESK2.sc.intel.com> On Mon, Jan 13, 2020 at 04:35:21PM -0800, 'Ira Weiny' wrote: > On Mon, Jan 13, 2020 at 02:19:57PM -0800, Darrick J. Wong wrote: > > On Fri, Jan 10, 2020 at 11:29:38AM -0800, ira.weiny@intel.com wrote: > > > From: Ira Weiny <ira.weiny@intel.com> > > [snip] > > > > > > > diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c > > > index 401da197f012..e8fd95b75e5b 100644 > > > --- a/fs/xfs/xfs_inode.c > > > +++ b/fs/xfs/xfs_inode.c > > > @@ -142,12 +142,12 @@ xfs_ilock_attr_map_shared( > > > * > > > * Basic locking order: > > > * > > > - * i_rwsem -> i_mmap_lock -> page_lock -> i_ilock > > > + * i_rwsem -> i_dax_sem -> i_mmap_lock -> page_lock -> i_ilock > > > > Mmmmmm, more locks. Can we skip the extra lock if CONFIG_FSDAX=n or if > > the filesystem devices don't support DAX at all? > > I'll look into it. > > > > > Also, I don't think we're actually following the i_rwsem -> i_daxsem > > order in fallocate, and possibly elsewhere too? > > I'll have to verify. It took a lot of iterations to get the order working so > I'm not going to claim perfection. Yes this was inconsistent. The code was right WRT i_rwsem. mmap_sem may have issues: What about this? diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c index c5d11b70d067..8808782a085e 100644 --- a/fs/xfs/xfs_inode.c +++ b/fs/xfs/xfs_inode.c @@ -142,12 +142,12 @@ xfs_ilock_attr_map_shared( * * Basic locking order: * - * i_rwsem -> i_dax_sem -> i_mmap_lock -> page_lock -> i_ilock + * i_dax_sem -> i_rwsem -> i_mmap_lock -> page_lock -> i_ilock * * mmap_sem locking order: * * i_rwsem -> page lock -> mmap_sem - * mmap_sem -> i_dax_sem -> i_mmap_lock -> page_lock + * i_dax_sem -> mmap_sem -> i_mmap_lock -> page_lock * * The difference in mmap_sem locking order mean that we cannot hold the * i_mmap_lock over syscall based read(2)/write(2) based IO. These IO paths can diff --git a/mm/mmap.c b/mm/mmap.c index e6b68924b7ca..b500aef30b27 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1547,18 +1547,12 @@ unsigned long do_mmap(struct file *file, unsigned long addr, vm_flags |= VM_NORESERVE; } - if (file) - lock_inode_mode(file_inode(file)); - addr = mmap_region(file, addr, len, vm_flags, pgoff, uf); if (!IS_ERR_VALUE(addr) && ((vm_flags & VM_LOCKED) || (flags & (MAP_POPULATE | MAP_NONBLOCK)) == MAP_POPULATE)) *populate = len; - if (file) - unlock_inode_mode(file_inode(file)); - return addr; } diff --git a/mm/util.c b/mm/util.c index 988d11e6c17c..1cfead8cd1ce 100644 --- a/mm/util.c +++ b/mm/util.c @@ -501,11 +501,18 @@ unsigned long vm_mmap_pgoff(struct file *file, unsigned long addr, ret = security_mmap_file(file, prot, flag); if (!ret) { - if (down_write_killable(&mm->mmap_sem)) + if (file) + lock_inode_mode(file_inode(file)); + if (down_write_killable(&mm->mmap_sem)) { + if (file) + unlock_inode_mode(file_inode(file)); return -EINTR; + } ret = do_mmap_pgoff(file, addr, len, prot, flag, pgoff, &populate, &uf); up_write(&mm->mmap_sem); + if (file) + unlock_inode_mode(file_inode(file)); userfaultfd_unmap_complete(mm, &uf); if (populate) mm_populate(ret, populate);
next prev parent reply index Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-01-10 19:29 [RFC PATCH V2 00/12] Enable per-file/directory DAX operations V2 ira.weiny 2020-01-10 19:29 ` [RFC PATCH V2 01/12] fs/stat: Define DAX statx attribute ira.weiny 2020-01-15 11:37 ` Jan Kara 2020-01-15 17:38 ` Darrick J. Wong 2020-01-15 19:45 ` Ira Weiny 2020-01-15 20:10 ` Dan Williams 2020-01-15 22:38 ` Ira Weiny 2020-01-16 5:39 ` Darrick J. Wong 2020-01-16 6:05 ` Dan Williams 2020-01-16 6:18 ` Darrick J. Wong 2020-01-16 6:25 ` Dan Williams 2020-01-18 9:11 ` Dave Chinner 2020-01-16 17:55 ` Ira Weiny 2020-01-16 18:04 ` Darrick J. Wong 2020-01-16 18:52 ` Ira Weiny 2020-01-16 22:19 ` Darrick J. Wong 2020-01-17 11:58 ` Jan Kara 2020-01-10 19:29 ` [RFC PATCH V2 02/12] fs/xfs: Isolate the physical DAX flag from effective ira.weiny 2020-01-10 19:29 ` [RFC PATCH V2 03/12] fs/xfs: Separate functionality of xfs_inode_supports_dax() ira.weiny 2020-01-10 19:29 ` [RFC PATCH V2 04/12] fs/xfs: Clean up DAX support check ira.weiny 2020-01-10 19:29 ` [RFC PATCH V2 05/12] fs: remove unneeded IS_DAX() check ira.weiny 2020-01-16 9:38 ` Jan Kara 2020-01-16 18:47 ` Ira Weiny 2020-01-10 19:29 ` [RFC PATCH V2 06/12] fs/xfs: Check if the inode supports DAX under lock ira.weiny 2020-01-10 19:29 ` [RFC PATCH V2 07/12] fs: Add locking for a dynamic inode 'mode' ira.weiny 2020-01-13 22:12 ` Darrick J. Wong 2020-01-14 0:20 ` Ira Weiny 2020-01-14 1:03 ` Darrick J. Wong 2020-01-15 19:08 ` Ira Weiny 2020-01-16 5:40 ` Darrick J. Wong 2020-01-16 18:54 ` Ira Weiny 2020-01-10 19:29 ` [RFC PATCH V2 08/12] fs/xfs: Add lock/unlock mode to xfs ira.weiny 2020-01-13 22:19 ` Darrick J. Wong 2020-01-14 0:35 ` Ira Weiny 2020-01-15 0:57 ` Ira Weiny [this message] 2020-01-15 23:52 ` Ira Weiny 2020-01-16 9:24 ` Jan Kara 2020-01-16 19:12 ` Ira Weiny 2020-01-10 19:29 ` [RFC PATCH V2 09/12] fs: Prevent mode change if file is mmap'ed ira.weiny 2020-01-13 22:22 ` Darrick J. Wong 2020-01-14 0:46 ` Ira Weiny 2020-01-14 1:30 ` Darrick J. Wong 2020-01-14 17:53 ` Ira Weiny 2020-01-15 11:34 ` Jan Kara 2020-01-15 18:24 ` Ira Weiny 2020-01-15 10:21 ` David Laight 2020-01-15 17:53 ` Ira Weiny 2020-01-10 19:29 ` [RFC PATCH V2 10/12] fs/xfs: Fix truncate up ira.weiny 2020-01-13 22:27 ` Darrick J. Wong 2020-01-14 0:40 ` Ira Weiny 2020-01-14 1:14 ` Darrick J. Wong 2020-01-14 19:00 ` Ira Weiny 2020-01-14 19:39 ` Ira Weiny 2020-01-10 19:29 ` [RFC PATCH V2 11/12] fs/xfs: Clean up locking in dax invalidate ira.weiny 2020-01-10 19:29 ` [RFC PATCH V2 12/12] fs/xfs: Allow toggle of effective DAX flag ira.weiny
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