From: John Groves <John@groves.net>
To: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: John Groves <jgroves@micron.com>,
Jonathan Corbet <corbet@lwn.net>,
Dan Williams <dan.j.williams@intel.com>,
Vishal Verma <vishal.l.verma@intel.com>,
Dave Jiang <dave.jiang@intel.com>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Christian Brauner <brauner@kernel.org>, Jan Kara <jack@suse.cz>,
Matthew Wilcox <willy@infradead.org>,
linux-cxl@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
nvdimm@lists.linux.dev, john@jagalactic.com,
Dave Chinner <david@fromorbit.com>,
Christoph Hellwig <hch@infradead.org>,
dave.hansen@linux.intel.com, gregory.price@memverge.com
Subject: Re: [RFC PATCH 05/20] dev_dax_iomap: Add dax_operations for use by fs-dax on devdax
Date: Mon, 26 Feb 2024 10:09:04 -0600 [thread overview]
Message-ID: <2cidhftdpd6t3zsbeafk5oty6uogtgfwkyysicsyyd5hbmmb7k@ebbbikzq4jyb> (raw)
In-Reply-To: <20240226123245.00000c01@Huawei.com>
On 24/02/26 12:32PM, Jonathan Cameron wrote:
> On Fri, 23 Feb 2024 11:41:49 -0600
> John Groves <John@Groves.net> wrote:
>
> > Notes about this commit:
> >
> > * These methods are based somewhat loosely on pmem_dax_ops from
> > drivers/nvdimm/pmem.c
> >
> > * dev_dax_direct_access() is returns the hpa, pfn and kva. The kva was
> > newly stored as dev_dax->virt_addr by dev_dax_probe().
> >
> > * The hpa/pfn are used for mmap (dax_iomap_fault()), and the kva is used
> > for read/write (dax_iomap_rw())
> >
> > * dev_dax_recovery_write() and dev_dax_zero_page_range() have not been
> > tested yet. I'm looking for suggestions as to how to test those.
> >
> > Signed-off-by: John Groves <john@groves.net>
> > ---
> > drivers/dax/bus.c | 107 ++++++++++++++++++++++++++++++++++++++++++++++
> > 1 file changed, 107 insertions(+)
> >
> > diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
> > index 664e8c1b9930..06fcda810674 100644
> > --- a/drivers/dax/bus.c
> > +++ b/drivers/dax/bus.c
> > @@ -10,6 +10,12 @@
> > #include "dax-private.h"
> > #include "bus.h"
> >
> > +#if IS_ENABLED(CONFIG_DEV_DAX_IOMAP)
> > +#include <linux/backing-dev.h>
> > +#include <linux/pfn_t.h>
> > +#include <linux/range.h>
> > +#endif
> > +
>
> Is it worth avoiding includes based on config? Probably not.
Just trying to demonstrate that I can be tedious :D
I'll drop the #if unless somebody disagrees.
>
> > static DEFINE_MUTEX(dax_bus_lock);
> >
> > #define DAX_NAME_LEN 30
> > @@ -1349,6 +1355,101 @@ __weak phys_addr_t dax_pgoff_to_phys(struct dev_dax *dev_dax, pgoff_t pgoff,
> > }
> > EXPORT_SYMBOL_GPL(dax_pgoff_to_phys);
> >
> > +#if IS_ENABLED(CONFIG_DEV_DAX_IOMAP)
> > +
>
> > +
> > +static long __dev_dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff,
> > + long nr_pages, enum dax_access_mode mode, void **kaddr,
> > + pfn_t *pfn)
> > +{
> > + struct dev_dax *dev_dax = dax_get_private(dax_dev);
> > + size_t dax_size = dev_dax_size(dev_dax);
> > + size_t size = nr_pages << PAGE_SHIFT;
> > + size_t offset = pgoff << PAGE_SHIFT;
> > + phys_addr_t phys;
> > + u64 virt_addr = dev_dax->virt_addr + offset;
> > + pfn_t local_pfn;
> > + u64 flags = PFN_DEV|PFN_MAP;
> > +
> > + WARN_ON(!dev_dax->virt_addr); /* virt_addr must be saved for direct_access */
> Fair enough, but from local code point of view, does it make sense to check this
> if !kaddr as we won't use this.
Hmm. This gets called with kaddr=NULL for mmap faults, and with non-NULL
kaddr for read/write (which need the virt_addr to do a memcpy variant).
If dev_dax->virt-addr is NULL, mmap will work but read/write will hork.
I lean toward keeping the warning. With these updates, it's broken if
read/write are broken.
> > +
> > + phys = dax_pgoff_to_phys(dev_dax, pgoff, nr_pages << PAGE_SHIFT);
> > +
> > + if (kaddr)
> > + *kaddr = (void *)virt_addr;
>
> Back to earlier comment on virt_addr as a void *. Definitely looking like
> that would be more accurate and simpler! Also not much point in computing
> virt_addr unless kaddr is good.
Yes, done (the void *).
the computation is copied directly from drivers/nvdimm/__pmem_direct_access() -
which does not warn if virt_addr is null. Actually I suppose this code should
just trust that dev_dax_probe sets virt_addr, and not warn?
So I'm now contradicting myself above...
>
> > +
> > + local_pfn = phys_to_pfn_t(phys, flags); /* are flags correct? */
> If you aren't going to do anything with it for !pfn, move it under the if (pfn).
>
> > + if (pfn)
> > + *pfn = local_pfn;
> > +
> > + /* This the valid size at the specified address */
> > + return PHYS_PFN(min_t(size_t, size, dax_size - offset));
> > +}
> > +
>
> > +
> > +static const struct dax_operations dev_dax_ops = {
> > + .direct_access = dev_dax_direct_access,
> > + .zero_page_range = dev_dax_zero_page_range,
> > + .recovery_write = dev_dax_recovery_write,
> > +};
> > +
> > +#endif /* IS_ENABLED(CONFIG_DEV_DAX_IOMAP) */
> > +
> > struct dev_dax *devm_create_dev_dax(struct dev_dax_data *data)
> > {
> > struct dax_region *dax_region = data->dax_region;
> > @@ -1404,11 +1505,17 @@ struct dev_dax *devm_create_dev_dax(struct dev_dax_data *data)
> > }
> > }
> >
>
> If we were to make this
>
> if (IS_ENABLED(CONFIG_DEV_DAX_IOMAP))
>
> etc can we avoid the ifdef stuff above and let dead code removal deal with it?
> Might need a few stubs - I haven't tried.
Better, thanks. No stubs needed.
>
> > +#if IS_ENABLED(CONFIG_DEV_DAX_IOMAP)
> > + /* holder_ops currently populated separately in a slightly hacky way */
> > + dax_dev = alloc_dax(dev_dax, &dev_dax_ops);
> > +#else
> > /*
> > * No dax_operations since there is no access to this device outside of
> > * mmap of the resulting character device.
> > */
> > dax_dev = alloc_dax(dev_dax, NULL);
> > +#endif
Thanks!
John
next prev parent reply other threads:[~2024-02-26 16:09 UTC|newest]
Thread overview: 105+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-23 17:41 [RFC PATCH 00/20] Introduce the famfs shared-memory file system John Groves
2024-02-23 17:41 ` [RFC PATCH 01/20] famfs: Documentation John Groves
2024-02-23 17:41 ` [RFC PATCH 02/20] dev_dax_iomap: Add fs_dax_get() func to prepare dax for fs-dax usage John Groves
2024-02-26 12:05 ` Jonathan Cameron
2024-02-26 15:00 ` John Groves
2024-02-23 17:41 ` [RFC PATCH 03/20] dev_dax_iomap: Move dax_pgoff_to_phys from device.c to bus.c since both need it now John Groves
2024-02-26 12:10 ` Jonathan Cameron
2024-02-26 15:13 ` John Groves
2024-02-23 17:41 ` [RFC PATCH 04/20] dev_dax_iomap: Save the kva from memremap John Groves
2024-02-26 12:21 ` Jonathan Cameron
2024-02-26 15:48 ` John Groves
2024-02-23 17:41 ` [RFC PATCH 05/20] dev_dax_iomap: Add dax_operations for use by fs-dax on devdax John Groves
2024-02-26 12:32 ` Jonathan Cameron
2024-02-26 16:09 ` John Groves [this message]
2024-02-23 17:41 ` [RFC PATCH 06/20] dev_dax_iomap: Add CONFIG_DEV_DAX_IOMAP kernel build parameter John Groves
2024-02-26 12:34 ` Jonathan Cameron
2024-02-26 16:12 ` John Groves
2024-02-23 17:41 ` [RFC PATCH 07/20] famfs: Add include/linux/famfs_ioctl.h John Groves
2024-02-24 1:39 ` Randy Dunlap
2024-02-24 2:23 ` John Groves
2024-02-24 3:27 ` Randy Dunlap
2024-02-24 23:32 ` John Groves
2024-02-24 23:40 ` Randy Dunlap
2024-02-26 12:39 ` Jonathan Cameron
2024-02-26 16:44 ` John Groves
2024-02-26 16:56 ` Jonathan Cameron
2024-02-26 18:04 ` John Groves
2024-02-23 17:41 ` [RFC PATCH 08/20] famfs: Add famfs_internal.h John Groves
2024-02-26 12:48 ` Jonathan Cameron
2024-02-26 17:35 ` John Groves
2024-02-27 10:28 ` Jonathan Cameron
2024-02-28 1:06 ` John Groves
2024-02-27 13:38 ` Christian Brauner
2024-02-27 14:12 ` John Groves
2024-02-23 17:41 ` [RFC PATCH 09/20] famfs: Add super_operations John Groves
2024-02-26 12:51 ` Jonathan Cameron
2024-02-26 21:47 ` John Groves
2024-02-27 10:34 ` Jonathan Cameron
2024-02-27 17:48 ` John Groves
2024-02-23 17:41 ` [RFC PATCH 10/20] famfs: famfs_open_device() & dax_holder_operations John Groves
2024-02-26 12:56 ` Jonathan Cameron
2024-02-26 22:22 ` John Groves
2024-02-27 13:39 ` Christian Brauner
2024-02-27 18:38 ` John Groves
2024-02-23 17:41 ` [RFC PATCH 11/20] famfs: Add fs_context_operations John Groves
2024-02-26 13:20 ` Jonathan Cameron
2024-02-26 22:43 ` John Groves
2024-02-27 13:41 ` Christian Brauner
2024-02-28 0:59 ` John Groves
2024-02-28 1:49 ` Randy Dunlap
2024-02-28 8:17 ` Christian Brauner
2024-02-28 10:07 ` Christian Brauner
2024-02-28 12:01 ` Christian Brauner
2024-02-23 17:41 ` [RFC PATCH 12/20] famfs: Add inode_operations and file_system_type John Groves
2024-02-26 13:25 ` Jonathan Cameron
2024-02-26 22:53 ` John Groves
2024-02-23 17:41 ` [RFC PATCH 13/20] famfs: Add iomap_ops John Groves
2024-02-26 13:30 ` Jonathan Cameron
2024-02-26 23:00 ` John Groves
2024-02-23 17:41 ` [RFC PATCH 14/20] famfs: Add struct file_operations John Groves
2024-02-26 13:32 ` Jonathan Cameron
2024-02-26 23:09 ` John Groves
2024-02-23 17:41 ` [RFC PATCH 15/20] famfs: Add ioctl to file_operations John Groves
2024-02-26 13:44 ` Jonathan Cameron
2024-02-23 17:42 ` [RFC PATCH 16/20] famfs: Add fault counters John Groves
2024-02-23 18:23 ` Dave Hansen
2024-02-23 19:56 ` John Groves
2024-02-23 20:04 ` Dan Williams
2024-02-23 20:39 ` John Groves
2024-02-23 21:19 ` Dave Hansen
2024-02-23 23:50 ` Dan Williams
2024-02-24 3:59 ` Matthew Wilcox
2024-02-24 4:30 ` Dan Williams
2024-02-23 17:42 ` [RFC PATCH 17/20] famfs: Add module stuff John Groves
2024-02-26 13:47 ` Jonathan Cameron
2024-02-27 22:15 ` John Groves
2024-02-23 17:42 ` [RFC PATCH 18/20] famfs: Support character dax via the dev_dax_iomap patch John Groves
2024-02-26 13:52 ` Jonathan Cameron
2024-02-27 22:27 ` John Groves
2024-02-23 17:42 ` [RFC PATCH 19/20] famfs: Update MAINTAINERS file John Groves
2024-02-23 17:42 ` [RFC PATCH 20/20] famfs: Add Kconfig and Makefile plumbing John Groves
2024-02-24 1:50 ` Randy Dunlap
2024-02-24 2:24 ` John Groves
2024-02-24 0:07 ` [RFC PATCH 00/20] Introduce the famfs shared-memory file system Luis Chamberlain
2024-02-26 13:27 ` John Groves
2024-02-26 15:53 ` Luis Chamberlain
2024-02-26 21:16 ` John Groves
2024-02-27 0:58 ` Luis Chamberlain
2024-02-27 2:05 ` John Groves
2024-02-29 2:15 ` Dave Chinner
2024-02-29 14:52 ` John Groves
2024-03-11 1:29 ` Dave Chinner
2024-02-29 6:52 ` Amir Goldstein
2024-02-29 22:16 ` John Groves
2024-05-17 9:55 ` Miklos Szeredi
2024-05-19 5:59 ` Amir Goldstein
2024-05-22 2:05 ` John Groves
2024-05-22 8:58 ` Miklos Szeredi
2024-05-22 10:16 ` Amir Goldstein
2024-05-22 11:28 ` Miklos Szeredi
2024-05-22 13:41 ` Amir Goldstein
2024-05-23 2:49 ` John Groves
2024-05-23 13:57 ` Miklos Szeredi
2024-05-24 0:47 ` John Groves
2024-05-24 7:55 ` Miklos Szeredi
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