Re: [PATCH 2/2 v2] f2fs: add a case of no need to read a page in write begin

[Jaegeuk Kim <jaegeuk@kernel.org>]

On 12/21, Chao Yu wrote:
> On 2016/12/21 2:03, Jaegeuk Kim wrote:
> > On 12/20, Yunlei He wrote:
> >> If the range we write cover the whole valid data in the last page,
> >> we do not need to read it.
> >>
> >> Signed-off-by: Yunlei He <heyunlei@huawei.com>
> >> ---
> >>  fs/f2fs/data.c | 5 ++++-
> >>  1 file changed, 4 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> >> index 9ac2625..303873f 100644
> >> --- a/fs/f2fs/data.c
> >> +++ b/fs/f2fs/data.c
> >> @@ -1715,6 +1715,9 @@ static int f2fs_write_begin(struct file *file, struct address_space *mapping,
> >>  	if (len == PAGE_SIZE || PageUptodate(page))
> >>  		return 0;
> >>  
> >> +	if (!(pos & (PAGE_SIZE - 1)) && (pos + len) >= i_size_read(inode))
> > 
> > I added here:
> > 		zero_user_segment(page, 0, PAGE_SIZE);
> 
> Only need to zeroout in range of [len, page_size] in the page.

Yup, fixed.

Thanks,

> 
> Thanks,
> 
> > 
> > Otherwise, xfstests/f2fs/001 gives a failure.
> > 
> > Thanks,
> > 
> >> +		return 0;
> >> +
> >>  	if (blkaddr == NEW_ADDR) {
> >>  		zero_user_segment(page, 0, PAGE_SIZE);
> >>  		SetPageUptodate(page);
> >> @@ -1768,7 +1771,7 @@ static int f2fs_write_end(struct file *file,
> >>  	 * let generic_perform_write() try to copy data again through copied=0.
> >>  	 */
> >>  	if (!PageUptodate(page)) {
> >> -		if (unlikely(copied != PAGE_SIZE))
> >> +		if (unlikely(copied != len))
> >>  			copied = 0;
> >>  		else
> >>  			SetPageUptodate(page);
> >> -- 
> >> 2.10.1
> >>
> >>
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> > .
> > 

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