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Date: Fri, 9 Oct 2020 18:30:36 -0700
From: Eric Biggers <ebiggers@kernel.org>
To: Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH RFC PKS/PMEM 22/58] fs/f2fs: Utilize new kmap_thread()
Message-ID: <20201010013036.GD1122@sol.localdomain>
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On Sat, Oct 10, 2020 at 01:39:54AM +0100, Matthew Wilcox wrote:
> On Fri, Oct 09, 2020 at 02:34:34PM -0700, Eric Biggers wrote:
> > On Fri, Oct 09, 2020 at 12:49:57PM -0700, ira.weiny@intel.com wrote:
> > > 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.
> > >
> > > @@ -2410,12 +2410,12 @@ static inline struct page *f2fs_pagecache_get_page(
> > >  
> > >  static inline void f2fs_copy_page(struct page *src, struct page *dst)
> > >  {
> > > -	char *src_kaddr = kmap(src);
> > > -	char *dst_kaddr = kmap(dst);
> > > +	char *src_kaddr = kmap_thread(src);
> > > +	char *dst_kaddr = kmap_thread(dst);
> > >  
> > >  	memcpy(dst_kaddr, src_kaddr, PAGE_SIZE);
> > > -	kunmap(dst);
> > > -	kunmap(src);
> > > +	kunmap_thread(dst);
> > > +	kunmap_thread(src);
> > >  }
> > 
> > Wouldn't it make more sense to switch cases like this to kmap_atomic()?
> > The pages are only mapped to do a memcpy(), then they're immediately unmapped.
> 
> Maybe you missed the earlier thread from Thomas trying to do something
> similar for rather different reasons ...
> 
> https://lore.kernel.org/lkml/20200919091751.011116649@linutronix.de/

I did miss it.  I'm not subscribed to any of the mailing lists it was sent to.

Anyway, it shouldn't matter.  Patchsets should be standalone, and not require
reading random prior threads on linux-kernel to understand.

And I still don't really understand.  After this patchset, there is still code
nearly identical to the above (doing a temporary mapping just for a memcpy) that
would still be using kmap_atomic().  Is the idea that later, such code will be
converted to use kmap_thread() instead?  If not, why use one over the other?

- Eric
_______________________________________________
Linux-nvdimm mailing list -- linux-nvdimm@lists.01.org
To unsubscribe send an email to linux-nvdimm-leave@lists.01.org

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Date:   Fri, 9 Oct 2020 18:30:36 -0700
From:   Eric Biggers <ebiggers@kernel.org>
To:     Matthew Wilcox <willy@infradead.org>
Cc:     ira.weiny@intel.com, Andrew Morton <akpm@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Andy Lutomirski <luto@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>, linux-aio@kvack.org,
        linux-efi@vger.kernel.org, kvm@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-mmc@vger.kernel.org,
        Dave Hansen <dave.hansen@linux.intel.com>,
        dri-devel@lists.freedesktop.org, linux-mm@kvack.org,
        target-devel@vger.kernel.org, linux-mtd@lists.infradead.org,
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        linux-cachefs@redhat.com, intel-wired-lan@lists.osuosl.org,
        xen-devel@lists.xenproject.org, linux-ext4@vger.kernel.org,
        Fenghua Yu <fenghua.yu@intel.com>, ecryptfs@vger.kernel.org,
        linux-um@lists.infradead.org, intel-gfx@lists.freedesktop.org,
        linux-erofs@lists.ozlabs.org, reiserfs-devel@vger.kernel.org,
        linux-block@vger.kernel.org, linux-bcache@vger.kernel.org,
        Jaegeuk Kim <jaegeuk@kernel.org>,
        Dan Williams <dan.j.williams@intel.com>,
        io-uring@vger.kernel.org, linux-nfs@vger.kernel.org,
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        linuxppc-dev@lists.ozlabs.org, linux-btrfs@vger.kernel.org
Subject: Re: [PATCH RFC PKS/PMEM 22/58] fs/f2fs: Utilize new kmap_thread()
Message-ID: <20201010013036.GD1122@sol.localdomain>
References: <20201009195033.3208459-1-ira.weiny@intel.com>
 <20201009195033.3208459-23-ira.weiny@intel.com>
 <20201009213434.GA839@sol.localdomain>
 <20201010003954.GW20115@casper.infradead.org>
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On Sat, Oct 10, 2020 at 01:39:54AM +0100, Matthew Wilcox wrote:
> On Fri, Oct 09, 2020 at 02:34:34PM -0700, Eric Biggers wrote:
> > On Fri, Oct 09, 2020 at 12:49:57PM -0700, ira.weiny@intel.com wrote:
> > > 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.
> > >
> > > @@ -2410,12 +2410,12 @@ static inline struct page *f2fs_pagecache_get_page(
> > >  
> > >  static inline void f2fs_copy_page(struct page *src, struct page *dst)
> > >  {
> > > -	char *src_kaddr = kmap(src);
> > > -	char *dst_kaddr = kmap(dst);
> > > +	char *src_kaddr = kmap_thread(src);
> > > +	char *dst_kaddr = kmap_thread(dst);
> > >  
> > >  	memcpy(dst_kaddr, src_kaddr, PAGE_SIZE);
> > > -	kunmap(dst);
> > > -	kunmap(src);
> > > +	kunmap_thread(dst);
> > > +	kunmap_thread(src);
> > >  }
> > 
> > Wouldn't it make more sense to switch cases like this to kmap_atomic()?
> > The pages are only mapped to do a memcpy(), then they're immediately unmapped.
> 
> Maybe you missed the earlier thread from Thomas trying to do something
> similar for rather different reasons ...
> 
> https://lore.kernel.org/lkml/20200919091751.011116649@linutronix.de/

I did miss it.  I'm not subscribed to any of the mailing lists it was sent to.

Anyway, it shouldn't matter.  Patchsets should be standalone, and not require
reading random prior threads on linux-kernel to understand.

And I still don't really understand.  After this patchset, there is still code
nearly identical to the above (doing a temporary mapping just for a memcpy) that
would still be using kmap_atomic().  Is the idea that later, such code will be
converted to use kmap_thread() instead?  If not, why use one over the other?

- Eric

From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Biggers <ebiggers@kernel.org>
Date: Sat, 10 Oct 2020 01:30:36 +0000
Subject: Re: [PATCH RFC PKS/PMEM 22/58] fs/f2fs: Utilize new kmap_thread()
Message-Id: <20201010013036.GD1122@sol.localdomain>
List-Id: <target-devel.vger.kernel.org>
References: <20201009195033.3208459-1-ira.weiny@intel.com>
 <20201009195033.3208459-23-ira.weiny@intel.com>
 <20201009213434.GA839@sol.localdomain>
 <20201010003954.GW20115@casper.infradead.org>
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To: Matthew Wilcox <willy@infradead.org>
Cc: linux-aio@kvack.org, linux-efi@vger.kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>, linux-mmc@vger.kernel.org, Dave Hansen <dave.hansen@linux.intel.com>, dri-devel@lists.freedesktop.org, linux-mm@kvack.org, target-devel@vger.kernel.org, linux-mtd@lists.infradead.org, linux-kselftest@vger.kernel.org, ira.weiny@intel.com, Thomas Gleixner <tglx@linutronix.de>, drbd-dev@lists.linbit.com, devel@driverdev.osuosl.org, linux-cifs@vger.kernel.org, linux-nilfs@vger.kernel.org, linux-scsi@vger.kernel.org, linux-nvdimm@lists.01.org, linux-rdma@vger.kernel.org, x86@kernel.org, amd-gfx@lists.freedesktop.org, linux-afs@lists.infradead.org, cluster-devel@redhat.com, Ingo Molnar <mingo@redhat.com>, intel-wired-lan@lists.osuosl.org, kexec@lists.infradead.org, xen-devel@lists.xenproject.org, linux-ext4@vger.kernel.org, bpf@vger.kernel.org, Dan Williams <dan.j.williams@intel.com>, Fenghua Yu <fenghua.yu@intel.com>, intel-gfx@lists.freedesktop.org, ecryptfs@vger.kernel.org, linux-um@lists.infradead.org, reiserfs-devel@vger.kernel.org, linux-block@vger.kernel.org, linux-bcache@vger.kernel.org, Borislav Petkov <bp@alien8.de>, Andy Lutomirski <luto@kernel.org>, Jaegeuk Kim <jaegeuk@kernel.org>, ceph-devel@vger.kernel.org, io-uring@vger.kernel.org, linux-cachefs@redhat.com, linux-nfs@vger.kernel.org, linux-ntfs-dev@lists.sourceforge.net, netdev@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, samba-technical@lists.samba.org, linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-fsdevel@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org>, linux-erofs@lists.ozlabs.org, linux-btrfs@vger.kernel.org

On Sat, Oct 10, 2020 at 01:39:54AM +0100, Matthew Wilcox wrote:
> On Fri, Oct 09, 2020 at 02:34:34PM -0700, Eric Biggers wrote:
> > On Fri, Oct 09, 2020 at 12:49:57PM -0700, ira.weiny@intel.com wrote:
> > > 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.
> > >
> > > @@ -2410,12 +2410,12 @@ static inline struct page *f2fs_pagecache_get_page(
> > >  
> > >  static inline void f2fs_copy_page(struct page *src, struct page *dst)
> > >  {
> > > -	char *src_kaddr = kmap(src);
> > > -	char *dst_kaddr = kmap(dst);
> > > +	char *src_kaddr = kmap_thread(src);
> > > +	char *dst_kaddr = kmap_thread(dst);
> > >  
> > >  	memcpy(dst_kaddr, src_kaddr, PAGE_SIZE);
> > > -	kunmap(dst);
> > > -	kunmap(src);
> > > +	kunmap_thread(dst);
> > > +	kunmap_thread(src);
> > >  }
> > 
> > Wouldn't it make more sense to switch cases like this to kmap_atomic()?
> > The pages are only mapped to do a memcpy(), then they're immediately unmapped.
> 
> Maybe you missed the earlier thread from Thomas trying to do something
> similar for rather different reasons ...
> 
> https://lore.kernel.org/lkml/20200919091751.011116649@linutronix.de/

I did miss it.  I'm not subscribed to any of the mailing lists it was sent to.

Anyway, it shouldn't matter.  Patchsets should be standalone, and not require
reading random prior threads on linux-kernel to understand.

And I still don't really understand.  After this patchset, there is still code
nearly identical to the above (doing a temporary mapping just for a memcpy) that
would still be using kmap_atomic().  Is the idea that later, such code will be
converted to use kmap_thread() instead?  If not, why use one over the other?

- Eric

From mboxrd@z Thu Jan  1 00:00:00 1970
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Date: Fri, 9 Oct 2020 18:30:36 -0700
From: Eric Biggers <ebiggers@kernel.org>
To: Matthew Wilcox <willy@infradead.org>
Message-ID: <20201010013036.GD1122@sol.localdomain>
References: <20201009195033.3208459-1-ira.weiny@intel.com>
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Subject: Re: [f2fs-dev] [PATCH RFC PKS/PMEM 22/58] fs/f2fs: Utilize new
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On Sat, Oct 10, 2020 at 01:39:54AM +0100, Matthew Wilcox wrote:
> On Fri, Oct 09, 2020 at 02:34:34PM -0700, Eric Biggers wrote:
> > On Fri, Oct 09, 2020 at 12:49:57PM -0700, ira.weiny@intel.com wrote:
> > > 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.
> > >
> > > @@ -2410,12 +2410,12 @@ static inline struct page *f2fs_pagecache_get_page(
> > >  
> > >  static inline void f2fs_copy_page(struct page *src, struct page *dst)
> > >  {
> > > -	char *src_kaddr = kmap(src);
> > > -	char *dst_kaddr = kmap(dst);
> > > +	char *src_kaddr = kmap_thread(src);
> > > +	char *dst_kaddr = kmap_thread(dst);
> > >  
> > >  	memcpy(dst_kaddr, src_kaddr, PAGE_SIZE);
> > > -	kunmap(dst);
> > > -	kunmap(src);
> > > +	kunmap_thread(dst);
> > > +	kunmap_thread(src);
> > >  }
> > 
> > Wouldn't it make more sense to switch cases like this to kmap_atomic()?
> > The pages are only mapped to do a memcpy(), then they're immediately unmapped.
> 
> Maybe you missed the earlier thread from Thomas trying to do something
> similar for rather different reasons ...
> 
> https://lore.kernel.org/lkml/20200919091751.011116649@linutronix.de/

I did miss it.  I'm not subscribed to any of the mailing lists it was sent to.

Anyway, it shouldn't matter.  Patchsets should be standalone, and not require
reading random prior threads on linux-kernel to understand.

And I still don't really understand.  After this patchset, there is still code
nearly identical to the above (doing a temporary mapping just for a memcpy) that
would still be using kmap_atomic().  Is the idea that later, such code will be
converted to use kmap_thread() instead?  If not, why use one over the other?

- Eric


_______________________________________________
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Date: Fri, 9 Oct 2020 18:30:36 -0700
From: Eric Biggers <ebiggers@kernel.org>
To: Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH RFC PKS/PMEM 22/58] fs/f2fs: Utilize new kmap_thread()
Message-ID: <20201010013036.GD1122@sol.localdomain>
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On Sat, Oct 10, 2020 at 01:39:54AM +0100, Matthew Wilcox wrote:
> On Fri, Oct 09, 2020 at 02:34:34PM -0700, Eric Biggers wrote:
> > On Fri, Oct 09, 2020 at 12:49:57PM -0700, ira.weiny@intel.com wrote:
> > > 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.
> > >
> > > @@ -2410,12 +2410,12 @@ static inline struct page *f2fs_pagecache_get_page(
> > >  
> > >  static inline void f2fs_copy_page(struct page *src, struct page *dst)
> > >  {
> > > -	char *src_kaddr = kmap(src);
> > > -	char *dst_kaddr = kmap(dst);
> > > +	char *src_kaddr = kmap_thread(src);
> > > +	char *dst_kaddr = kmap_thread(dst);
> > >  
> > >  	memcpy(dst_kaddr, src_kaddr, PAGE_SIZE);
> > > -	kunmap(dst);
> > > -	kunmap(src);
> > > +	kunmap_thread(dst);
> > > +	kunmap_thread(src);
> > >  }
> > 
> > Wouldn't it make more sense to switch cases like this to kmap_atomic()?
> > The pages are only mapped to do a memcpy(), then they're immediately unmapped.
> 
> Maybe you missed the earlier thread from Thomas trying to do something
> similar for rather different reasons ...
> 
> https://lore.kernel.org/lkml/20200919091751.011116649@linutronix.de/

I did miss it.  I'm not subscribed to any of the mailing lists it was sent to.

Anyway, it shouldn't matter.  Patchsets should be standalone, and not require
reading random prior threads on linux-kernel to understand.

And I still don't really understand.  After this patchset, there is still code
nearly identical to the above (doing a temporary mapping just for a memcpy) that
would still be using kmap_atomic().  Is the idea that later, such code will be
converted to use kmap_thread() instead?  If not, why use one over the other?

- Eric
_______________________________________________
devel mailing list
devel@linuxdriverproject.org
http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel

From mboxrd@z Thu Jan  1 00:00:00 1970
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Date: Fri, 9 Oct 2020 18:30:36 -0700
From: Eric Biggers <ebiggers@kernel.org>
To: Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH RFC PKS/PMEM 22/58] fs/f2fs: Utilize new kmap_thread()
Message-ID: <20201010013036.GD1122@sol.localdomain>
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On Sat, Oct 10, 2020 at 01:39:54AM +0100, Matthew Wilcox wrote:
> On Fri, Oct 09, 2020 at 02:34:34PM -0700, Eric Biggers wrote:
> > On Fri, Oct 09, 2020 at 12:49:57PM -0700, ira.weiny@intel.com wrote:
> > > 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.
> > >
> > > @@ -2410,12 +2410,12 @@ static inline struct page *f2fs_pagecache_get_page(
> > >  
> > >  static inline void f2fs_copy_page(struct page *src, struct page *dst)
> > >  {
> > > -	char *src_kaddr = kmap(src);
> > > -	char *dst_kaddr = kmap(dst);
> > > +	char *src_kaddr = kmap_thread(src);
> > > +	char *dst_kaddr = kmap_thread(dst);
> > >  
> > >  	memcpy(dst_kaddr, src_kaddr, PAGE_SIZE);
> > > -	kunmap(dst);
> > > -	kunmap(src);
> > > +	kunmap_thread(dst);
> > > +	kunmap_thread(src);
> > >  }
> > 
> > Wouldn't it make more sense to switch cases like this to kmap_atomic()?
> > The pages are only mapped to do a memcpy(), then they're immediately unmapped.
> 
> Maybe you missed the earlier thread from Thomas trying to do something
> similar for rather different reasons ...
> 
> https://lore.kernel.org/lkml/20200919091751.011116649@linutronix.de/

I did miss it.  I'm not subscribed to any of the mailing lists it was sent to.

Anyway, it shouldn't matter.  Patchsets should be standalone, and not require
reading random prior threads on linux-kernel to understand.

And I still don't really understand.  After this patchset, there is still code
nearly identical to the above (doing a temporary mapping just for a memcpy) that
would still be using kmap_atomic().  Is the idea that later, such code will be
converted to use kmap_thread() instead?  If not, why use one over the other?

- Eric

From mboxrd@z Thu Jan  1 00:00:00 1970
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Date: Fri, 9 Oct 2020 18:30:36 -0700
From: Eric Biggers <ebiggers@kernel.org>
To: Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH RFC PKS/PMEM 22/58] fs/f2fs: Utilize new kmap_thread()
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On Sat, Oct 10, 2020 at 01:39:54AM +0100, Matthew Wilcox wrote:
> On Fri, Oct 09, 2020 at 02:34:34PM -0700, Eric Biggers wrote:
> > On Fri, Oct 09, 2020 at 12:49:57PM -0700, ira.weiny@intel.com wrote:
> > > 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.
> > >
> > > @@ -2410,12 +2410,12 @@ static inline struct page *f2fs_pagecache_get_page(
> > >  
> > >  static inline void f2fs_copy_page(struct page *src, struct page *dst)
> > >  {
> > > -	char *src_kaddr = kmap(src);
> > > -	char *dst_kaddr = kmap(dst);
> > > +	char *src_kaddr = kmap_thread(src);
> > > +	char *dst_kaddr = kmap_thread(dst);
> > >  
> > >  	memcpy(dst_kaddr, src_kaddr, PAGE_SIZE);
> > > -	kunmap(dst);
> > > -	kunmap(src);
> > > +	kunmap_thread(dst);
> > > +	kunmap_thread(src);
> > >  }
> > 
> > Wouldn't it make more sense to switch cases like this to kmap_atomic()?
> > The pages are only mapped to do a memcpy(), then they're immediately unmapped.
> 
> Maybe you missed the earlier thread from Thomas trying to do something
> similar for rather different reasons ...
> 
> https://lore.kernel.org/lkml/20200919091751.011116649@linutronix.de/

I did miss it.  I'm not subscribed to any of the mailing lists it was sent to.

Anyway, it shouldn't matter.  Patchsets should be standalone, and not require
reading random prior threads on linux-kernel to understand.

And I still don't really understand.  After this patchset, there is still code
nearly identical to the above (doing a temporary mapping just for a memcpy) that
would still be using kmap_atomic().  Is the idea that later, such code will be
converted to use kmap_thread() instead?  If not, why use one over the other?

- Eric

______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/

From mboxrd@z Thu Jan  1 00:00:00 1970
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Date: Fri, 9 Oct 2020 18:30:36 -0700
From: Eric Biggers <ebiggers@kernel.org>
To: Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH RFC PKS/PMEM 22/58] fs/f2fs: Utilize new kmap_thread()
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On Sat, Oct 10, 2020 at 01:39:54AM +0100, Matthew Wilcox wrote:
> On Fri, Oct 09, 2020 at 02:34:34PM -0700, Eric Biggers wrote:
> > On Fri, Oct 09, 2020 at 12:49:57PM -0700, ira.weiny@intel.com wrote:
> > > 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.
> > >
> > > @@ -2410,12 +2410,12 @@ static inline struct page *f2fs_pagecache_get_page(
> > >  
> > >  static inline void f2fs_copy_page(struct page *src, struct page *dst)
> > >  {
> > > -	char *src_kaddr = kmap(src);
> > > -	char *dst_kaddr = kmap(dst);
> > > +	char *src_kaddr = kmap_thread(src);
> > > +	char *dst_kaddr = kmap_thread(dst);
> > >  
> > >  	memcpy(dst_kaddr, src_kaddr, PAGE_SIZE);
> > > -	kunmap(dst);
> > > -	kunmap(src);
> > > +	kunmap_thread(dst);
> > > +	kunmap_thread(src);
> > >  }
> > 
> > Wouldn't it make more sense to switch cases like this to kmap_atomic()?
> > The pages are only mapped to do a memcpy(), then they're immediately unmapped.
> 
> Maybe you missed the earlier thread from Thomas trying to do something
> similar for rather different reasons ...
> 
> https://lore.kernel.org/lkml/20200919091751.011116649@linutronix.de/

I did miss it.  I'm not subscribed to any of the mailing lists it was sent to.

Anyway, it shouldn't matter.  Patchsets should be standalone, and not require
reading random prior threads on linux-kernel to understand.

And I still don't really understand.  After this patchset, there is still code
nearly identical to the above (doing a temporary mapping just for a memcpy) that
would still be using kmap_atomic().  Is the idea that later, such code will be
converted to use kmap_thread() instead?  If not, why use one over the other?

- Eric
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel

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Date: Fri, 9 Oct 2020 18:30:36 -0700
From: Eric Biggers <ebiggers@kernel.org>
To: Matthew Wilcox <willy@infradead.org>
Message-ID: <20201010013036.GD1122@sol.localdomain>
References: <20201009195033.3208459-1-ira.weiny@intel.com>
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On Sat, Oct 10, 2020 at 01:39:54AM +0100, Matthew Wilcox wrote:
> On Fri, Oct 09, 2020 at 02:34:34PM -0700, Eric Biggers wrote:
> > On Fri, Oct 09, 2020 at 12:49:57PM -0700, ira.weiny@intel.com wrote:
> > > 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.
> > >
> > > @@ -2410,12 +2410,12 @@ static inline struct page *f2fs_pagecache_get_page(
> > >  
> > >  static inline void f2fs_copy_page(struct page *src, struct page *dst)
> > >  {
> > > -	char *src_kaddr = kmap(src);
> > > -	char *dst_kaddr = kmap(dst);
> > > +	char *src_kaddr = kmap_thread(src);
> > > +	char *dst_kaddr = kmap_thread(dst);
> > >  
> > >  	memcpy(dst_kaddr, src_kaddr, PAGE_SIZE);
> > > -	kunmap(dst);
> > > -	kunmap(src);
> > > +	kunmap_thread(dst);
> > > +	kunmap_thread(src);
> > >  }
> > 
> > Wouldn't it make more sense to switch cases like this to kmap_atomic()?
> > The pages are only mapped to do a memcpy(), then they're immediately unmapped.
> 
> Maybe you missed the earlier thread from Thomas trying to do something
> similar for rather different reasons ...
> 
> https://lore.kernel.org/lkml/20200919091751.011116649@linutronix.de/

I did miss it.  I'm not subscribed to any of the mailing lists it was sent to.

Anyway, it shouldn't matter.  Patchsets should be standalone, and not require
reading random prior threads on linux-kernel to understand.

And I still don't really understand.  After this patchset, there is still code
nearly identical to the above (doing a temporary mapping just for a memcpy) that
would still be using kmap_atomic().  Is the idea that later, such code will be
converted to use kmap_thread() instead?  If not, why use one over the other?

- Eric
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx

From mboxrd@z Thu Jan  1 00:00:00 1970
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Date: Fri, 9 Oct 2020 18:30:36 -0700
From: Eric Biggers <ebiggers@kernel.org>
To: Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH RFC PKS/PMEM 22/58] fs/f2fs: Utilize new kmap_thread()
Message-ID: <20201010013036.GD1122@sol.localdomain>
References: <20201009195033.3208459-1-ira.weiny@intel.com>
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On Sat, Oct 10, 2020 at 01:39:54AM +0100, Matthew Wilcox wrote:
> On Fri, Oct 09, 2020 at 02:34:34PM -0700, Eric Biggers wrote:
> > On Fri, Oct 09, 2020 at 12:49:57PM -0700, ira.weiny@intel.com wrote:
> > > 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.
> > >
> > > @@ -2410,12 +2410,12 @@ static inline struct page *f2fs_pagecache_get_page(
> > >  
> > >  static inline void f2fs_copy_page(struct page *src, struct page *dst)
> > >  {
> > > -	char *src_kaddr = kmap(src);
> > > -	char *dst_kaddr = kmap(dst);
> > > +	char *src_kaddr = kmap_thread(src);
> > > +	char *dst_kaddr = kmap_thread(dst);
> > >  
> > >  	memcpy(dst_kaddr, src_kaddr, PAGE_SIZE);
> > > -	kunmap(dst);
> > > -	kunmap(src);
> > > +	kunmap_thread(dst);
> > > +	kunmap_thread(src);
> > >  }
> > 
> > Wouldn't it make more sense to switch cases like this to kmap_atomic()?
> > The pages are only mapped to do a memcpy(), then they're immediately unmapped.
> 
> Maybe you missed the earlier thread from Thomas trying to do something
> similar for rather different reasons ...
> 
> https://lore.kernel.org/lkml/20200919091751.011116649@linutronix.de/

I did miss it.  I'm not subscribed to any of the mailing lists it was sent to.

Anyway, it shouldn't matter.  Patchsets should be standalone, and not require
reading random prior threads on linux-kernel to understand.

And I still don't really understand.  After this patchset, there is still code
nearly identical to the above (doing a temporary mapping just for a memcpy) that
would still be using kmap_atomic().  Is the idea that later, such code will be
converted to use kmap_thread() instead?  If not, why use one over the other?

- Eric
_______________________________________________
amd-gfx mailing list
amd-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/amd-gfx

From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Biggers <ebiggers@kernel.org>
Date: Fri, 9 Oct 2020 18:30:36 -0700
Subject: [Intel-wired-lan] [PATCH RFC PKS/PMEM 22/58] fs/f2fs: Utilize
 new kmap_thread()
In-Reply-To: <20201010003954.GW20115@casper.infradead.org>
References: <20201009195033.3208459-1-ira.weiny@intel.com>
 <20201009195033.3208459-23-ira.weiny@intel.com>
 <20201009213434.GA839@sol.localdomain>
 <20201010003954.GW20115@casper.infradead.org>
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On Sat, Oct 10, 2020 at 01:39:54AM +0100, Matthew Wilcox wrote:
> On Fri, Oct 09, 2020 at 02:34:34PM -0700, Eric Biggers wrote:
> > On Fri, Oct 09, 2020 at 12:49:57PM -0700, ira.weiny at intel.com wrote:
> > > 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.
> > >
> > > @@ -2410,12 +2410,12 @@ static inline struct page *f2fs_pagecache_get_page(
> > >  
> > >  static inline void f2fs_copy_page(struct page *src, struct page *dst)
> > >  {
> > > -	char *src_kaddr = kmap(src);
> > > -	char *dst_kaddr = kmap(dst);
> > > +	char *src_kaddr = kmap_thread(src);
> > > +	char *dst_kaddr = kmap_thread(dst);
> > >  
> > >  	memcpy(dst_kaddr, src_kaddr, PAGE_SIZE);
> > > -	kunmap(dst);
> > > -	kunmap(src);
> > > +	kunmap_thread(dst);
> > > +	kunmap_thread(src);
> > >  }
> > 
> > Wouldn't it make more sense to switch cases like this to kmap_atomic()?
> > The pages are only mapped to do a memcpy(), then they're immediately unmapped.
> 
> Maybe you missed the earlier thread from Thomas trying to do something
> similar for rather different reasons ...
> 
> https://lore.kernel.org/lkml/20200919091751.011116649 at linutronix.de/

I did miss it.  I'm not subscribed to any of the mailing lists it was sent to.

Anyway, it shouldn't matter.  Patchsets should be standalone, and not require
reading random prior threads on linux-kernel to understand.

And I still don't really understand.  After this patchset, there is still code
nearly identical to the above (doing a temporary mapping just for a memcpy) that
would still be using kmap_atomic().  Is the idea that later, such code will be
converted to use kmap_thread() instead?  If not, why use one over the other?

- Eric

From mboxrd@z Thu Jan  1 00:00:00 1970
Return-path: <kexec-bounces+dwmw2=infradead.org@lists.infradead.org>
Date: Fri, 9 Oct 2020 18:30:36 -0700
From: Eric Biggers <ebiggers@kernel.org>
Subject: Re: [PATCH RFC PKS/PMEM 22/58] fs/f2fs: Utilize new kmap_thread()
Message-ID: <20201010013036.GD1122@sol.localdomain>
References: <20201009195033.3208459-1-ira.weiny@intel.com>
 <20201009195033.3208459-23-ira.weiny@intel.com>
 <20201009213434.GA839@sol.localdomain>
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To: Matthew Wilcox <willy@infradead.org>
Cc: linux-aio@kvack.org, linux-efi@vger.kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>, linux-mmc@vger.kernel.org, Dave Hansen <dave.hansen@linux.intel.com>, dri-devel@lists.freedesktop.org, linux-mm@kvack.org, target-devel@vger.kernel.org, linux-mtd@lists.infradead.org, linux-kselftest@vger.kernel.org, ira.weiny@intel.com, Thomas Gleixner <tglx@linutronix.de>, drbd-dev@lists.linbit.com, devel@driverdev.osuosl.org, linux-cifs@vger.kernel.org, linux-nilfs@vger.kernel.org, linux-scsi@vger.kernel.org, linux-nvdimm@lists.01.org, linux-rdma@vger.kernel.org, x86@kernel.org, amd-gfx@lists.freedesktop.org, linux-afs@lists.infradead.org, cluster-devel@redhat.com, Ingo Molnar <mingo@redhat.com>, intel-wired-lan@lists.osuosl.org, kexec@lists.infradead.org, xen-devel@lists.xenproject.org, linux-ext4@vger.kernel.org, bpf@vger.kernel.org, Dan Williams <dan.j.williams@intel.com>, Fenghua Yu <fenghua.yu@intel.com>, intel-gfx@lists.freedesktop.org, ecryptfs@vger.kernel.org, linux-um@lists.infradead.org, reiserfs-devel@vger.kernel.org, linux-block@vger.kernel.org, linux-bcache@vger.kernel.org, Borislav Petkov <bp@alien8.de>, Andy Lutomirski <luto@kernel.org>, Jaegeuk Kim <jaegeuk@kernel.org>, ceph-devel@vger.kernel.org, io-uring@vger.kernel.org, linux-cachefs@redhat.com, linux-nfs@vger.kernel.org, linux-ntfs-dev@lists.sourceforge.net, netdev@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, samba-technical@lists.samba.org, linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-fsdevel@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org>, linux-erofs@lists.ozlabs.org, linux-btrfs@vger.kernel.org

On Sat, Oct 10, 2020 at 01:39:54AM +0100, Matthew Wilcox wrote:
> On Fri, Oct 09, 2020 at 02:34:34PM -0700, Eric Biggers wrote:
> > On Fri, Oct 09, 2020 at 12:49:57PM -0700, ira.weiny@intel.com wrote:
> > > 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.
> > >
> > > @@ -2410,12 +2410,12 @@ static inline struct page *f2fs_pagecache_get_page(
> > >  
> > >  static inline void f2fs_copy_page(struct page *src, struct page *dst)
> > >  {
> > > -	char *src_kaddr = kmap(src);
> > > -	char *dst_kaddr = kmap(dst);
> > > +	char *src_kaddr = kmap_thread(src);
> > > +	char *dst_kaddr = kmap_thread(dst);
> > >  
> > >  	memcpy(dst_kaddr, src_kaddr, PAGE_SIZE);
> > > -	kunmap(dst);
> > > -	kunmap(src);
> > > +	kunmap_thread(dst);
> > > +	kunmap_thread(src);
> > >  }
> > 
> > Wouldn't it make more sense to switch cases like this to kmap_atomic()?
> > The pages are only mapped to do a memcpy(), then they're immediately unmapped.
> 
> Maybe you missed the earlier thread from Thomas trying to do something
> similar for rather different reasons ...
> 
> https://lore.kernel.org/lkml/20200919091751.011116649@linutronix.de/

I did miss it.  I'm not subscribed to any of the mailing lists it was sent to.

Anyway, it shouldn't matter.  Patchsets should be standalone, and not require
reading random prior threads on linux-kernel to understand.

And I still don't really understand.  After this patchset, there is still code
nearly identical to the above (doing a temporary mapping just for a memcpy) that
would still be using kmap_atomic().  Is the idea that later, such code will be
converted to use kmap_thread() instead?  If not, why use one over the other?

- Eric

_______________________________________________
kexec mailing list
kexec@lists.infradead.org
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From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Biggers <ebiggers@kernel.org>
Date: Fri, 9 Oct 2020 18:30:36 -0700
Subject: [Cluster-devel] [PATCH RFC PKS/PMEM 22/58] fs/f2fs: Utilize new
	kmap_thread()
In-Reply-To: <20201010003954.GW20115@casper.infradead.org>
References: <20201009195033.3208459-1-ira.weiny@intel.com>
	<20201009195033.3208459-23-ira.weiny@intel.com>
	<20201009213434.GA839@sol.localdomain>
	<20201010003954.GW20115@casper.infradead.org>
Message-ID: <20201010013036.GD1122@sol.localdomain>
List-Id: <cluster-devel.redhat.com>
To: cluster-devel.redhat.com
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On Sat, Oct 10, 2020 at 01:39:54AM +0100, Matthew Wilcox wrote:
> On Fri, Oct 09, 2020 at 02:34:34PM -0700, Eric Biggers wrote:
> > On Fri, Oct 09, 2020 at 12:49:57PM -0700, ira.weiny at intel.com wrote:
> > > 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.
> > >
> > > @@ -2410,12 +2410,12 @@ static inline struct page *f2fs_pagecache_get_page(
> > >  
> > >  static inline void f2fs_copy_page(struct page *src, struct page *dst)
> > >  {
> > > -	char *src_kaddr = kmap(src);
> > > -	char *dst_kaddr = kmap(dst);
> > > +	char *src_kaddr = kmap_thread(src);
> > > +	char *dst_kaddr = kmap_thread(dst);
> > >  
> > >  	memcpy(dst_kaddr, src_kaddr, PAGE_SIZE);
> > > -	kunmap(dst);
> > > -	kunmap(src);
> > > +	kunmap_thread(dst);
> > > +	kunmap_thread(src);
> > >  }
> > 
> > Wouldn't it make more sense to switch cases like this to kmap_atomic()?
> > The pages are only mapped to do a memcpy(), then they're immediately unmapped.
> 
> Maybe you missed the earlier thread from Thomas trying to do something
> similar for rather different reasons ...
> 
> https://lore.kernel.org/lkml/20200919091751.011116649 at linutronix.de/

I did miss it.  I'm not subscribed to any of the mailing lists it was sent to.

Anyway, it shouldn't matter.  Patchsets should be standalone, and not require
reading random prior threads on linux-kernel to understand.

And I still don't really understand.  After this patchset, there is still code
nearly identical to the above (doing a temporary mapping just for a memcpy) that
would still be using kmap_atomic().  Is the idea that later, such code will be
converted to use kmap_thread() instead?  If not, why use one over the other?

- Eric