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[RFC,PKS/PMEM,24/58] fs/freevxfs: Utilize new kmap_thread()

Message ID 20201009195033.3208459-25-ira.weiny@intel.com
State New
Headers show
Series PMEM: Introduce stray write protection for PMEM | expand

Commit Message

Ira Weiny Oct. 9, 2020, 7:49 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: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
---
 fs/freevxfs/vxfs_immed.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

Ira Weiny Oct. 13, 2020, 8:52 p.m. UTC | #1 
On Tue, Oct 13, 2020 at 12:25:44PM +0100, Christoph Hellwig wrote:
> > -	kaddr = kmap(pp);
> > +	kaddr = kmap_thread(pp);
> >  	memcpy(kaddr, vip->vii_immed.vi_immed + offset, PAGE_SIZE);
> > -	kunmap(pp);
> > +	kunmap_thread(pp);
> 
> You only Cced me on this particular patch, which means I have absolutely
> no idea what kmap_thread and kunmap_thread actually do, and thus can't
> provide an informed review.

Sorry the list was so big I struggled with who to CC and on which patches.

> 
> That being said I think your life would be a lot easier if you add
> helpers for the above code sequence and its counterpart that copies
> to a potential hughmem page first, as that hides the implementation
> details from most users.

Matthew Wilcox and Al Viro have suggested similar ideas.

https://lore.kernel.org/lkml/20201013205012.GI2046448@iweiny-DESK2.sc.intel.com/

Ira
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Patch

diff --git a/fs/freevxfs/vxfs_immed.c b/fs/freevxfs/vxfs_immed.c
index bfc780c682fb..9c42fec4cd85 100644
--- a/fs/freevxfs/vxfs_immed.c
+++ b/fs/freevxfs/vxfs_immed.c
@@ -69,9 +69,9 @@  vxfs_immed_readpage(struct file *fp, struct page *pp)
 	u_int64_t	offset = (u_int64_t)pp->index << PAGE_SHIFT;
 	caddr_t		kaddr;
 
-	kaddr = kmap(pp);
+	kaddr = kmap_thread(pp);
 	memcpy(kaddr, vip->vii_immed.vi_immed + offset, PAGE_SIZE);
-	kunmap(pp);
+	kunmap_thread(pp);
 	
 	flush_dcache_page(pp);
 	SetPageUptodate(pp);