Re: [PATCH 3/3] fs/dax: Assigning NULL to gfn of dax_direct_access if useless
From: Dan Williams
Date: Wed Jul 04 2018 - 10:37:49 EST
On Wed, Jul 4, 2018 at 6:07 AM, Huaisheng Ye <yehs2007@xxxxxxxx> wrote:
> ---- On Wed, 04 Jul 2018 19:30:12 +0800 Jan Kara <jack@xxxxxxx> wrote ----
> > On Wed 04-07-18 14:40:58, Huaisheng Ye wrote:
> > > From: Huaisheng Ye <yehs1@xxxxxxxxxx>
> > >
> > > Some functions within fs/dax don't need to get gfn from direct_access.
> > > Assigning NULL to gfn of dax_direct_access is more intuitive and simple
> > > than offering a useless local variable.
> > >
> > > Signed-off-by: Huaisheng Ye <yehs1@xxxxxxxxxx>
> >
> > I like this. You can add:
> >
> > Reviewed-by: Jan Kara <jack@xxxxxxx>
> >
> > for the series.
> >
> > Honza
> >
> I am so happy you like them, thank you very much.
Yes, I like this too. In fact I have a similar patch in my tree
already that I have been preparing to send out. I am using it to delay
when we need to have the 'struct page' memmap for dax initialized.
Attached is the full patch, but the series is still a work in
progress.
From 62e12abebacbafdb5218a92501885fe0e80ea922 Mon Sep 17 00:00:00 2001
From: Dan Williams <dan.j.williams@xxxxxxxxx>
Date: Wed, 27 Jun 2018 22:21:30 -0700
Subject: [PATCH] dax: Elide pfn lookups
When not required, allow drivers to skip returning a pfn if one was not
requested. In support of asynchronous initialization of 'struct page'
there needs to be a sync point at which the memmap is made valid. The
latest point where the kernel can reasonably sync is when a pfn is being
used to populate userspace page tables. Otherwise, if only the kernel
address is needed from dax_direct_access(), typically in-kernel users,
then the 'pfn_t *' argument to dax_direct_access() can be NULL.
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
drivers/dax/super.c | 17 +++++++++++------
drivers/nvdimm/pmem.c | 3 ++-
drivers/s390/block/dcssblk.c | 5 +++--
fs/dax.c | 10 +++-------
tools/testing/nvdimm/pmem-dax.c | 6 ++++--
5 files changed, 23 insertions(+), 18 deletions(-)
diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index 3b1fe4b6b00e..82256506e40b 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -72,7 +72,7 @@ struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev)
EXPORT_SYMBOL_GPL(fs_dax_get_by_bdev);
#endif
-static bool validate_dax_pfn(pfn_t pfn)
+static bool validate_dax_pfn(pfn_t *pfn)
{
bool dax_enabled = false;
@@ -84,7 +84,7 @@ static bool validate_dax_pfn(pfn_t pfn)
if (!IS_ENABLED(CONFIG_DAX_DRIVER_DEBUG))
return true;
- if (IS_ENABLED(CONFIG_FS_DAX_LIMITED) && pfn_t_special(pfn)) {
+ if (IS_ENABLED(CONFIG_FS_DAX_LIMITED) && pfn_t_special(*pfn)) {
/*
* An arch that has enabled the pmem api should also
* have its drivers support pfn_t_devmap()
@@ -95,10 +95,10 @@ static bool validate_dax_pfn(pfn_t pfn)
*/
WARN_ON(IS_ENABLED(CONFIG_ARCH_HAS_PMEM_API));
dax_enabled = true;
- } else if (pfn_t_devmap(pfn)) {
+ } else if (pfn_t_devmap(*pfn)) {
struct dev_pagemap *pgmap;
- pgmap = get_dev_pagemap(pfn_t_to_pfn(pfn), NULL);
+ pgmap = get_dev_pagemap(pfn_t_to_pfn(*pfn), NULL);
if (pgmap && pgmap->type == MEMORY_DEVICE_FS_DAX)
dax_enabled = true;
put_dev_pagemap(pgmap);
@@ -120,10 +120,10 @@ static bool validate_dax_pfn(pfn_t pfn)
bool __bdev_dax_supported(struct block_device *bdev, int blocksize)
{
struct dax_device *dax_dev;
+ pfn_t _pfn, *pfn;
pgoff_t pgoff;
int err, id;
void *kaddr;
- pfn_t pfn;
long len;
char buf[BDEVNAME_SIZE];
@@ -147,8 +147,13 @@ bool __bdev_dax_supported(struct block_device *bdev, int blocksize)
return false;
}
+ if (IS_ENABLED(DAX_DRIVER_DEBUG))
+ pfn = &_pfn;
+ else
+ pfn = NULL;
+
id = dax_read_lock();
- len = dax_direct_access(dax_dev, pgoff, 1, &kaddr, &pfn);
+ len = dax_direct_access(dax_dev, pgoff, 1, &kaddr, pfn);
dax_read_unlock(id);
put_dax(dax_dev);
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index e8ac6f244d2b..c430536320a5 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -228,7 +228,8 @@ __weak long __pmem_direct_access(struct pmem_device *pmem, pgoff_t pgoff,
PFN_PHYS(nr_pages))))
return -EIO;
*kaddr = pmem->virt_addr + offset;
- *pfn = phys_to_pfn_t(pmem->phys_addr + offset, pmem->pfn_flags);
+ if (pfn)
+ *pfn = phys_to_pfn_t(pmem->phys_addr + offset, pmem->pfn_flags);
/*
* If badblocks are present, limit known good range to the
diff --git a/drivers/s390/block/dcssblk.c b/drivers/s390/block/dcssblk.c
index ed607288e696..a645b2c93c34 100644
--- a/drivers/s390/block/dcssblk.c
+++ b/drivers/s390/block/dcssblk.c
@@ -923,8 +923,9 @@ __dcssblk_direct_access(struct dcssblk_dev_info *dev_info, pgoff_t pgoff,
dev_sz = dev_info->end - dev_info->start + 1;
*kaddr = (void *) dev_info->start + offset;
- *pfn = __pfn_to_pfn_t(PFN_DOWN(dev_info->start + offset),
- PFN_DEV|PFN_SPECIAL);
+ if (pfn)
+ *pfn = __pfn_to_pfn_t(PFN_DOWN(dev_info->start + offset),
+ PFN_DEV|PFN_SPECIAL);
return (dev_sz - offset) / PAGE_SIZE;
}
diff --git a/fs/dax.c b/fs/dax.c
index 641192808bb6..28264ff4e343 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -647,7 +647,6 @@ static int copy_user_dax(struct block_device *bdev, struct dax_device *dax_dev,
{
void *vto, *kaddr;
pgoff_t pgoff;
- pfn_t pfn;
long rc;
int id;
@@ -656,7 +655,7 @@ static int copy_user_dax(struct block_device *bdev, struct dax_device *dax_dev,
return rc;
id = dax_read_lock();
- rc = dax_direct_access(dax_dev, pgoff, PHYS_PFN(size), &kaddr, &pfn);
+ rc = dax_direct_access(dax_dev, pgoff, PHYS_PFN(size), &kaddr, NULL);
if (rc < 0) {
dax_read_unlock(id);
return rc;
@@ -1052,15 +1051,13 @@ int __dax_zero_page_range(struct block_device *bdev,
pgoff_t pgoff;
long rc, id;
void *kaddr;
- pfn_t pfn;
rc = bdev_dax_pgoff(bdev, sector, PAGE_SIZE, &pgoff);
if (rc)
return rc;
id = dax_read_lock();
- rc = dax_direct_access(dax_dev, pgoff, 1, &kaddr,
- &pfn);
+ rc = dax_direct_access(dax_dev, pgoff, 1, &kaddr, NULL);
if (rc < 0) {
dax_read_unlock(id);
return rc;
@@ -1116,7 +1113,6 @@ dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
ssize_t map_len;
pgoff_t pgoff;
void *kaddr;
- pfn_t pfn;
if (fatal_signal_pending(current)) {
ret = -EINTR;
@@ -1128,7 +1124,7 @@ dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
break;
map_len = dax_direct_access(dax_dev, pgoff, PHYS_PFN(size),
- &kaddr, &pfn);
+ &kaddr, NULL);
if (map_len < 0) {
ret = map_len;
break;
diff --git a/tools/testing/nvdimm/pmem-dax.c b/tools/testing/nvdimm/pmem-dax.c
index b53596ad601b..d4cb5281b30e 100644
--- a/tools/testing/nvdimm/pmem-dax.c
+++ b/tools/testing/nvdimm/pmem-dax.c
@@ -33,7 +33,8 @@ long __pmem_direct_access(struct pmem_device *pmem, pgoff_t pgoff,
*kaddr = pmem->virt_addr + offset;
page = vmalloc_to_page(pmem->virt_addr + offset);
- *pfn = page_to_pfn_t(page);
+ if (pfn)
+ *pfn = page_to_pfn_t(page);
pr_debug_ratelimited("%s: pmem: %p pgoff: %#lx pfn: %#lx\n",
__func__, pmem, pgoff, page_to_pfn(page));
@@ -41,7 +42,8 @@ long __pmem_direct_access(struct pmem_device *pmem, pgoff_t pgoff,
}
*kaddr = pmem->virt_addr + offset;
- *pfn = phys_to_pfn_t(pmem->phys_addr + offset, pmem->pfn_flags);
+ if (pfn)
+ *pfn = phys_to_pfn_t(pmem->phys_addr + offset, pmem->pfn_flags);
/*
* If badblocks are present, limit known good range to the
--
2.13.6