From: Ross Zwisler Subject: Re: [PATCH v4 07/12] dax: coordinate locking for offsets in PMD range Date: Mon, 3 Oct 2016 12:40:02 -0600 Message-ID: <20161003184002.GB2044@linux.intel.com> References: <1475189370-31634-1-git-send-email-ross.zwisler@linux.intel.com> <1475189370-31634-8-git-send-email-ross.zwisler@linux.intel.com> <20161003095518.GM6457@quack2.suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Theodore Ts'o , Matthew Wilcox , Dave Chinner , linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Christoph Hellwig , linux-xfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, Andreas Dilger , Alexander Viro , Jan Kara , linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-ext4-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Andrew Morton To: Jan Kara Return-path: Content-Disposition: inline In-Reply-To: <20161003095518.GM6457-4I4JzKEfoa/jFM9bn6wA6Q@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-nvdimm-bounces-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org Sender: "Linux-nvdimm" List-Id: linux-ext4.vger.kernel.org On Mon, Oct 03, 2016 at 11:55:18AM +0200, Jan Kara wrote: > On Thu 29-09-16 16:49:25, Ross Zwisler wrote: > > DAX radix tree locking currently locks entries based on the unique > > combination of the 'mapping' pointer and the pgoff_t 'index' for the entry. > > This works for PTEs, but as we move to PMDs we will need to have all the > > offsets within the range covered by the PMD to map to the same bit lock. > > To accomplish this, for ranges covered by a PMD entry we will instead lock > > based on the page offset of the beginning of the PMD entry. The 'mapping' > > pointer is still used in the same way. > > > > Signed-off-by: Ross Zwisler > > --- > > fs/dax.c | 37 ++++++++++++++++++++++++------------- > > include/linux/dax.h | 2 +- > > mm/filemap.c | 2 +- > > 3 files changed, 26 insertions(+), 15 deletions(-) > > > > diff --git a/fs/dax.c b/fs/dax.c > > index baef586..406feea 100644 > > --- a/fs/dax.c > > +++ b/fs/dax.c > > @@ -64,10 +64,17 @@ static int __init init_dax_wait_table(void) > > } > > fs_initcall(init_dax_wait_table); > > > > +static pgoff_t dax_entry_start(pgoff_t index, void *entry) > > +{ > > + if (RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD) > > + index &= (PMD_MASK >> PAGE_SHIFT); > > Hum, but if we shift right, top bits of PMD_MASK will become zero - not > something we want I guess... You rather want to mask with something like: > ~((1UL << (PMD_SHIFT - PAGE_SHIFT)) - 1) Great catch, thanks. Fixed for v5. > > @@ -447,10 +457,11 @@ restart: > > return entry; > > } > > > > -void dax_wake_mapping_entry_waiter(struct address_space *mapping, > > +void dax_wake_mapping_entry_waiter(void *entry, struct address_space *mapping, > > pgoff_t index, bool wake_all) > > Nitpick: Ordering of arguments would look more logical to me like: > > dax_wake_mapping_entry_waiter(mapping, index, entry, wake_all) Cool, I'll reorder them for v5. Thanks for the review!