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From: Eric Biggers <ebiggers@kernel.org>
To: Matthew Wilcox <willy@infradead.org>
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Subject: Re: [PATCH RFC PKS/PMEM 22/58] fs/f2fs: Utilize new kmap_thread()
Date: Fri, 9 Oct 2020 18:30:36 -0700
Message-ID: <20201010013036.GD1122@sol.localdomain> (raw)
In-Reply-To: <20201010003954.GW20115@casper.infradead.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

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  reply index

Thread overview: 93+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-09 19:49 [PATCH RFC PKS/PMEM 00/58] PMEM: Introduce stray write protection for PMEM ira.weiny
2020-10-09 19:49 ` [PATCH RFC PKS/PMEM 01/58] x86/pks: Add a global pkrs option ira.weiny
2020-10-09 19:49 ` [PATCH RFC PKS/PMEM 02/58] x86/pks/test: Add testing for global option ira.weiny
2020-10-09 19:49 ` [PATCH RFC PKS/PMEM 03/58] memremap: Add zone device access protection ira.weiny
2020-10-09 19:49 ` [PATCH RFC PKS/PMEM 04/58] kmap: Add stray access protection for device pages ira.weiny
2020-10-09 19:49 ` [PATCH RFC PKS/PMEM 05/58] kmap: Introduce k[un]map_thread ira.weiny
2020-11-10  1:13   ` Thomas Gleixner
2020-11-10  4:59     ` Ira Weiny
2020-11-10  8:48       ` Thomas Gleixner
2020-10-09 19:49 ` [PATCH RFC PKS/PMEM 06/58] kmap: Introduce k[un]map_thread debugging ira.weiny
2020-10-09 19:49 ` [PATCH RFC PKS/PMEM 07/58] drivers/drbd: Utilize new kmap_thread() ira.weiny
2020-10-09 19:49 ` [PATCH RFC PKS/PMEM 08/58] drivers/firmware_loader: " ira.weiny
2020-10-09 19:49 ` [PATCH RFC PKS/PMEM 09/58] drivers/gpu: " ira.weiny
2020-10-09 22:03   ` Daniel Vetter
2020-10-10 23:01     ` Ira Weiny
2020-10-09 19:49 ` [PATCH RFC PKS/PMEM 10/58] drivers/rdma: " ira.weiny
2020-10-09 19:49 ` [PATCH RFC PKS/PMEM 11/58] drivers/net: " ira.weiny
2020-10-09 19:49 ` [PATCH RFC PKS/PMEM 12/58] fs/afs: " ira.weiny
2020-10-09 19:49 ` [PATCH RFC PKS/PMEM 13/58] fs/btrfs: " ira.weiny
2020-10-09 19:49 ` [PATCH RFC PKS/PMEM 14/58] fs/cifs: " ira.weiny
2020-10-09 19:49 ` [PATCH RFC PKS/PMEM 15/58] fs/ecryptfs: " ira.weiny
2020-10-09 19:49 ` [PATCH RFC PKS/PMEM 16/58] fs/gfs2: " ira.weiny
2020-10-09 19:49 ` [PATCH RFC PKS/PMEM 17/58] fs/nilfs2: " ira.weiny
2020-10-09 19:49 ` [PATCH RFC PKS/PMEM 18/58] fs/hfs: " ira.weiny
2020-10-09 19:49 ` [PATCH RFC PKS/PMEM 19/58] fs/hfsplus: " ira.weiny
2020-10-09 19:49 ` [PATCH RFC PKS/PMEM 20/58] fs/jffs2: " ira.weiny
2020-10-09 19:49 ` [PATCH RFC PKS/PMEM 21/58] fs/nfs: " ira.weiny
2020-10-09 19:49 ` [PATCH RFC PKS/PMEM 22/58] fs/f2fs: " ira.weiny
2020-10-09 21:34   ` Eric Biggers
2020-10-10  0:39     ` Matthew Wilcox
2020-10-10  1:30       ` Eric Biggers [this message]
2020-10-12  6:56         ` Ira Weiny
2020-10-12 16:19           ` Eric Biggers
2020-10-12 16:28             ` Dave Hansen
2020-10-12 16:44               ` Matthew Wilcox
2020-10-12 19:53                 ` Ira Weiny
2020-10-12 20:02                   ` Matthew Wilcox
2020-10-12 23:31                     ` Ira Weiny
2020-10-10  2:43     ` James Bottomley
2020-10-09 19:49 ` [PATCH RFC PKS/PMEM 23/58] fs/fuse: " ira.weiny
2020-10-09 19:49 ` [PATCH RFC PKS/PMEM 24/58] fs/freevxfs: " ira.weiny
2020-10-13 11:25   ` Christoph Hellwig
2020-10-13 20:52     ` Ira Weiny
2020-10-09 19:50 ` [PATCH RFC PKS/PMEM 25/58] fs/reiserfs: " ira.weiny
2020-10-09 19:50 ` [PATCH RFC PKS/PMEM 26/58] fs/zonefs: " ira.weiny
2020-10-12  2:30   ` Damien Le Moal
2020-10-09 19:50 ` [PATCH RFC PKS/PMEM 27/58] fs/ubifs: " ira.weiny
2020-10-09 19:50 ` [PATCH RFC PKS/PMEM 28/58] fs/cachefiles: " ira.weiny
2020-10-09 19:50 ` [PATCH RFC PKS/PMEM 29/58] fs/ntfs: " ira.weiny
2020-10-09 19:50 ` [PATCH RFC PKS/PMEM 30/58] fs/romfs: " ira.weiny
2020-10-09 19:50 ` [PATCH RFC PKS/PMEM 31/58] fs/vboxsf: " ira.weiny
2020-10-09 19:50 ` [PATCH RFC PKS/PMEM 32/58] fs/hostfs: " ira.weiny
2020-10-09 19:50 ` [PATCH RFC PKS/PMEM 33/58] fs/cramfs: " ira.weiny
2020-10-13 18:36   ` Nicolas Pitre
2020-10-13 18:44   ` Dan Williams
2020-10-13 19:36     ` Matthew Wilcox
2020-10-13 19:41       ` Dan Williams
2020-10-13 20:01       ` Al Viro
2020-10-13 20:50         ` Ira Weiny
2020-10-13 20:45       ` Ira Weiny
2020-10-09 19:50 ` [PATCH RFC PKS/PMEM 34/58] fs/erofs: " ira.weiny
2020-10-09 19:50 ` [PATCH RFC PKS/PMEM 35/58] fs: " ira.weiny
2020-10-09 19:50 ` [PATCH RFC PKS/PMEM 36/58] fs/ext2: Use ext2_put_page ira.weiny
2020-10-09 19:50 ` [PATCH RFC PKS/PMEM 37/58] fs/ext2: Utilize new kmap_thread() ira.weiny
2020-10-09 19:50 ` [PATCH RFC PKS/PMEM 38/58] fs/isofs: " ira.weiny
2020-10-09 19:50 ` [PATCH RFC PKS/PMEM 39/58] fs/jffs2: " ira.weiny
2020-10-09 19:50 ` [PATCH RFC PKS/PMEM 40/58] net: " ira.weiny
2020-10-09 19:50 ` [PATCH RFC PKS/PMEM 41/58] drivers/target: " ira.weiny
2020-10-09 19:50 ` [PATCH RFC PKS/PMEM 42/58] drivers/scsi: " ira.weiny
2020-10-09 19:50 ` [PATCH RFC PKS/PMEM 43/58] drivers/mmc: " ira.weiny
2020-10-09 19:50 ` [PATCH RFC PKS/PMEM 44/58] drivers/xen: " ira.weiny
2020-10-09 19:50 ` [PATCH RFC PKS/PMEM 45/58] drivers/firmware: " ira.weiny
2020-10-09 19:50 ` [PATCH RFC PKS/PMEM 46/58] drives/staging: " ira.weiny
2020-10-09 19:50 ` [PATCH RFC PKS/PMEM 47/58] drivers/mtd: " ira.weiny
2020-10-09 19:50 ` [PATCH RFC PKS/PMEM 48/58] drivers/md: " ira.weiny
2020-10-10  2:20   ` Coly Li
2020-10-12  5:28     ` Ira Weiny
2020-10-12  7:40       ` Coly Li
2020-10-09 19:50 ` [PATCH RFC PKS/PMEM 49/58] drivers/misc: " ira.weiny
2020-10-09 19:50 ` [PATCH RFC PKS/PMEM 50/58] drivers/android: " ira.weiny
2020-10-09 19:50 ` [PATCH RFC PKS/PMEM 51/58] kernel: " ira.weiny
2020-10-10  3:43   ` Eric W. Biederman
2020-10-09 19:50 ` [PATCH RFC PKS/PMEM 52/58] mm: " ira.weiny
2020-10-09 19:50 ` [PATCH RFC PKS/PMEM 53/58] lib: " ira.weiny
2020-10-09 19:50 ` [PATCH RFC PKS/PMEM 54/58] powerpc: " ira.weiny
2020-10-09 19:50 ` [PATCH RFC PKS/PMEM 55/58] samples: " ira.weiny
2020-10-09 19:50 ` [PATCH RFC PKS/PMEM 56/58] dax: Stray access protection for dax_direct_access() ira.weiny
2020-10-09 19:50 ` [PATCH RFC PKS/PMEM 57/58] nvdimm/pmem: Stray access protection for pmem->virt_addr ira.weiny
2020-10-10  2:53   ` John Hubbard
2020-10-12  5:52     ` Ira Weiny
2020-10-09 19:50 ` [PATCH RFC PKS/PMEM 58/58] [dax|pmem]: Enable stray access protection ira.weiny
2020-10-10 11:36 ` [PATCH RFC PKS/PMEM 10/58] drivers/rdma: Utilize new kmap_thread() Bernard Metzler
2020-10-12  4:47   ` Ira Weiny

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