diff mbox series

[RFC,PKS/PMEM,33/58] fs/cramfs: Utilize new kmap_thread()

Message ID 20201009195033.3208459-34-ira.weiny@intel.com
State New
Headers show
Series PMEM: Introduce stray write protection for PMEM | expand

Commit Message

Ira Weiny Oct. 9, 2020, 7:50 p.m. UTC
From: Ira Weiny <ira.weiny@intel.com>

The kmap() calls in this FS are localized to a single thread.  To avoid
the over head of global PKRS updates use the new kmap_thread() call.

Cc: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
---
 fs/cramfs/inode.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

Comments

Nicolas Pitre Oct. 13, 2020, 6:36 p.m. UTC | #1
On Fri, 9 Oct 2020, ira.weiny@intel.com wrote:

> From: Ira Weiny <ira.weiny@intel.com>
> 
> The kmap() calls in this FS are localized to a single thread.  To avoid
> the over head of global PKRS updates use the new kmap_thread() call.
> 
> Cc: Nicolas Pitre <nico@fluxnic.net>
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>

Acked-by: Nicolas Pitre <nico@fluxnic.net>

>  fs/cramfs/inode.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/cramfs/inode.c b/fs/cramfs/inode.c
> index 912308600d39..003c014a42ed 100644
> --- a/fs/cramfs/inode.c
> +++ b/fs/cramfs/inode.c
> @@ -247,8 +247,8 @@ static void *cramfs_blkdev_read(struct super_block *sb, unsigned int offset,
>  		struct page *page = pages[i];
>  
>  		if (page) {
> -			memcpy(data, kmap(page), PAGE_SIZE);
> -			kunmap(page);
> +			memcpy(data, kmap_thread(page), PAGE_SIZE);
> +			kunmap_thread(page);
>  			put_page(page);
>  		} else
>  			memset(data, 0, PAGE_SIZE);
> @@ -826,7 +826,7 @@ static int cramfs_readpage(struct file *file, struct page *page)
>  
>  	maxblock = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
>  	bytes_filled = 0;
> -	pgdata = kmap(page);
> +	pgdata = kmap_thread(page);
>  
>  	if (page->index < maxblock) {
>  		struct super_block *sb = inode->i_sb;
> @@ -914,13 +914,13 @@ static int cramfs_readpage(struct file *file, struct page *page)
>  
>  	memset(pgdata + bytes_filled, 0, PAGE_SIZE - bytes_filled);
>  	flush_dcache_page(page);
> -	kunmap(page);
> +	kunmap_thread(page);
>  	SetPageUptodate(page);
>  	unlock_page(page);
>  	return 0;
>  
>  err:
> -	kunmap(page);
> +	kunmap_thread(page);
>  	ClearPageUptodate(page);
>  	SetPageError(page);
>  	unlock_page(page);
> -- 
> 2.28.0.rc0.12.gb6a658bd00c9
> 
>
Dan Williams Oct. 13, 2020, 6:44 p.m. UTC | #2
On Fri, Oct 9, 2020 at 12:52 PM <ira.weiny@intel.com> wrote:
>
> From: Ira Weiny <ira.weiny@intel.com>
>
> The kmap() calls in this FS are localized to a single thread.  To avoid
> the over head of global PKRS updates use the new kmap_thread() call.
>
> Cc: Nicolas Pitre <nico@fluxnic.net>
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>
> ---
>  fs/cramfs/inode.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/fs/cramfs/inode.c b/fs/cramfs/inode.c
> index 912308600d39..003c014a42ed 100644
> --- a/fs/cramfs/inode.c
> +++ b/fs/cramfs/inode.c
> @@ -247,8 +247,8 @@ static void *cramfs_blkdev_read(struct super_block *sb, unsigned int offset,
>                 struct page *page = pages[i];
>
>                 if (page) {
> -                       memcpy(data, kmap(page), PAGE_SIZE);
> -                       kunmap(page);
> +                       memcpy(data, kmap_thread(page), PAGE_SIZE);
> +                       kunmap_thread(page);

Why does this need a sleepable kmap? This looks like a textbook
kmap_atomic() use case.
Matthew Wilcox Oct. 13, 2020, 7:36 p.m. UTC | #3
On Tue, Oct 13, 2020 at 11:44:29AM -0700, Dan Williams wrote:
> On Fri, Oct 9, 2020 at 12:52 PM <ira.weiny@intel.com> wrote:
> >
> > From: Ira Weiny <ira.weiny@intel.com>
> >
> > The kmap() calls in this FS are localized to a single thread.  To avoid
> > the over head of global PKRS updates use the new kmap_thread() call.
> >
> > Cc: Nicolas Pitre <nico@fluxnic.net>
> > Signed-off-by: Ira Weiny <ira.weiny@intel.com>
> > ---
> >  fs/cramfs/inode.c | 10 +++++-----
> >  1 file changed, 5 insertions(+), 5 deletions(-)
> >
> > diff --git a/fs/cramfs/inode.c b/fs/cramfs/inode.c
> > index 912308600d39..003c014a42ed 100644
> > --- a/fs/cramfs/inode.c
> > +++ b/fs/cramfs/inode.c
> > @@ -247,8 +247,8 @@ static void *cramfs_blkdev_read(struct super_block *sb, unsigned int offset,
> >                 struct page *page = pages[i];
> >
> >                 if (page) {
> > -                       memcpy(data, kmap(page), PAGE_SIZE);
> > -                       kunmap(page);
> > +                       memcpy(data, kmap_thread(page), PAGE_SIZE);
> > +                       kunmap_thread(page);
> 
> Why does this need a sleepable kmap? This looks like a textbook
> kmap_atomic() use case.

There's a lot of code of this form.  Could we perhaps have:

static inline void copy_to_highpage(struct page *to, void *vfrom, unsigned int size)
{
	char *vto = kmap_atomic(to);

	memcpy(vto, vfrom, size);
	kunmap_atomic(vto);
}

in linux/highmem.h ?
Dan Williams Oct. 13, 2020, 7:41 p.m. UTC | #4
On Tue, Oct 13, 2020 at 12:37 PM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Tue, Oct 13, 2020 at 11:44:29AM -0700, Dan Williams wrote:
> > On Fri, Oct 9, 2020 at 12:52 PM <ira.weiny@intel.com> wrote:
> > >
> > > From: Ira Weiny <ira.weiny@intel.com>
> > >
> > > The kmap() calls in this FS are localized to a single thread.  To avoid
> > > the over head of global PKRS updates use the new kmap_thread() call.
> > >
> > > Cc: Nicolas Pitre <nico@fluxnic.net>
> > > Signed-off-by: Ira Weiny <ira.weiny@intel.com>
> > > ---
> > >  fs/cramfs/inode.c | 10 +++++-----
> > >  1 file changed, 5 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/fs/cramfs/inode.c b/fs/cramfs/inode.c
> > > index 912308600d39..003c014a42ed 100644
> > > --- a/fs/cramfs/inode.c
> > > +++ b/fs/cramfs/inode.c
> > > @@ -247,8 +247,8 @@ static void *cramfs_blkdev_read(struct super_block *sb, unsigned int offset,
> > >                 struct page *page = pages[i];
> > >
> > >                 if (page) {
> > > -                       memcpy(data, kmap(page), PAGE_SIZE);
> > > -                       kunmap(page);
> > > +                       memcpy(data, kmap_thread(page), PAGE_SIZE);
> > > +                       kunmap_thread(page);
> >
> > Why does this need a sleepable kmap? This looks like a textbook
> > kmap_atomic() use case.
>
> There's a lot of code of this form.  Could we perhaps have:
>
> static inline void copy_to_highpage(struct page *to, void *vfrom, unsigned int size)
> {
>         char *vto = kmap_atomic(to);
>
>         memcpy(vto, vfrom, size);
>         kunmap_atomic(vto);
> }
>
> in linux/highmem.h ?

Nice, yes, that could also replace the local ones in lib/iov_iter.c
(memcpy_{to,from}_page())
Al Viro Oct. 13, 2020, 8:01 p.m. UTC | #5
On Tue, Oct 13, 2020 at 08:36:43PM +0100, Matthew Wilcox wrote:

> static inline void copy_to_highpage(struct page *to, void *vfrom, unsigned int size)
> {
> 	char *vto = kmap_atomic(to);
> 
> 	memcpy(vto, vfrom, size);
> 	kunmap_atomic(vto);
> }
> 
> in linux/highmem.h ?

You mean, like
static void memcpy_from_page(char *to, struct page *page, size_t offset, size_t len)
{
        char *from = kmap_atomic(page);
        memcpy(to, from + offset, len);
        kunmap_atomic(from);
}

static void memcpy_to_page(struct page *page, size_t offset, const char *from, size_t len)
{
        char *to = kmap_atomic(page);
        memcpy(to + offset, from, len);
        kunmap_atomic(to);
}

static void memzero_page(struct page *page, size_t offset, size_t len)
{
        char *addr = kmap_atomic(page);
        memset(addr + offset, 0, len);
        kunmap_atomic(addr);
}

in lib/iov_iter.c?  FWIW, I don't like that "highpage" in the name and
highmem.h as location - these make perfect sense regardless of highmem;
they are normal memory operations with page + offset used instead of
a pointer...
Ira Weiny Oct. 13, 2020, 8:45 p.m. UTC | #6
On Tue, Oct 13, 2020 at 08:36:43PM +0100, Matthew Wilcox wrote:
> On Tue, Oct 13, 2020 at 11:44:29AM -0700, Dan Williams wrote:
> > On Fri, Oct 9, 2020 at 12:52 PM <ira.weiny@intel.com> wrote:
> > >
> > > From: Ira Weiny <ira.weiny@intel.com>
> > >
> > > The kmap() calls in this FS are localized to a single thread.  To avoid
> > > the over head of global PKRS updates use the new kmap_thread() call.
> > >
> > > Cc: Nicolas Pitre <nico@fluxnic.net>
> > > Signed-off-by: Ira Weiny <ira.weiny@intel.com>
> > > ---
> > >  fs/cramfs/inode.c | 10 +++++-----
> > >  1 file changed, 5 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/fs/cramfs/inode.c b/fs/cramfs/inode.c
> > > index 912308600d39..003c014a42ed 100644
> > > --- a/fs/cramfs/inode.c
> > > +++ b/fs/cramfs/inode.c
> > > @@ -247,8 +247,8 @@ static void *cramfs_blkdev_read(struct super_block *sb, unsigned int offset,
> > >                 struct page *page = pages[i];
> > >
> > >                 if (page) {
> > > -                       memcpy(data, kmap(page), PAGE_SIZE);
> > > -                       kunmap(page);
> > > +                       memcpy(data, kmap_thread(page), PAGE_SIZE);
> > > +                       kunmap_thread(page);
> > 
> > Why does this need a sleepable kmap? This looks like a textbook
> > kmap_atomic() use case.
> 
> There's a lot of code of this form.  Could we perhaps have:
> 
> static inline void copy_to_highpage(struct page *to, void *vfrom, unsigned int size)
> {
> 	char *vto = kmap_atomic(to);
> 
> 	memcpy(vto, vfrom, size);
> 	kunmap_atomic(vto);
> }
> 
> in linux/highmem.h ?

Christoph had the same idea.  I'll work on it.

Ira
Ira Weiny Oct. 13, 2020, 8:50 p.m. UTC | #7
On Tue, Oct 13, 2020 at 09:01:49PM +0100, Al Viro wrote:
> On Tue, Oct 13, 2020 at 08:36:43PM +0100, Matthew Wilcox wrote:
> 
> > static inline void copy_to_highpage(struct page *to, void *vfrom, unsigned int size)
> > {
> > 	char *vto = kmap_atomic(to);
> > 
> > 	memcpy(vto, vfrom, size);
> > 	kunmap_atomic(vto);
> > }
> > 
> > in linux/highmem.h ?
> 
> You mean, like
> static void memcpy_from_page(char *to, struct page *page, size_t offset, size_t len)
> {
>         char *from = kmap_atomic(page);
>         memcpy(to, from + offset, len);
>         kunmap_atomic(from);
> }
> 
> static void memcpy_to_page(struct page *page, size_t offset, const char *from, size_t len)
> {
>         char *to = kmap_atomic(page);
>         memcpy(to + offset, from, len);
>         kunmap_atomic(to);
> }
> 
> static void memzero_page(struct page *page, size_t offset, size_t len)
> {
>         char *addr = kmap_atomic(page);
>         memset(addr + offset, 0, len);
>         kunmap_atomic(addr);
> }
> 
> in lib/iov_iter.c?  FWIW, I don't like that "highpage" in the name and
> highmem.h as location - these make perfect sense regardless of highmem;
> they are normal memory operations with page + offset used instead of
> a pointer...

I was thinking along those lines as well especially because of the direction
this patch set takes kmap().

Thanks for pointing these out to me.  How about I lift them to a common header?
But if not highmem.h where?

Ira
diff mbox series

Patch

diff --git a/fs/cramfs/inode.c b/fs/cramfs/inode.c
index 912308600d39..003c014a42ed 100644
--- a/fs/cramfs/inode.c
+++ b/fs/cramfs/inode.c
@@ -247,8 +247,8 @@  static void *cramfs_blkdev_read(struct super_block *sb, unsigned int offset,
 		struct page *page = pages[i];
 
 		if (page) {
-			memcpy(data, kmap(page), PAGE_SIZE);
-			kunmap(page);
+			memcpy(data, kmap_thread(page), PAGE_SIZE);
+			kunmap_thread(page);
 			put_page(page);
 		} else
 			memset(data, 0, PAGE_SIZE);
@@ -826,7 +826,7 @@  static int cramfs_readpage(struct file *file, struct page *page)
 
 	maxblock = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
 	bytes_filled = 0;
-	pgdata = kmap(page);
+	pgdata = kmap_thread(page);
 
 	if (page->index < maxblock) {
 		struct super_block *sb = inode->i_sb;
@@ -914,13 +914,13 @@  static int cramfs_readpage(struct file *file, struct page *page)
 
 	memset(pgdata + bytes_filled, 0, PAGE_SIZE - bytes_filled);
 	flush_dcache_page(page);
-	kunmap(page);
+	kunmap_thread(page);
 	SetPageUptodate(page);
 	unlock_page(page);
 	return 0;
 
 err:
-	kunmap(page);
+	kunmap_thread(page);
 	ClearPageUptodate(page);
 	SetPageError(page);
 	unlock_page(page);