[f2fs-dev] 答复: [PATCH -next] f2fs: add flush_dcache_page after page was written

[zhangqilong via Linux-f2fs-devel <linux-f2fs-devel@lists.sourceforge.net>]

> 
> On 2022/8/25 10:41, Zhang Qilong wrote:
> > If the written page was mapped more than twice, the written data here
> > will not be seen by others. We add the flush_dcache_page to fix it.
> >
> > Fixes:0a2aa8fbb9693 ("f2fs: refactor __exchange_data_block for speed
> > up")
> > Signed-off-by: Zhang Qilong <zhangqilong3@huawei.com>
> > ---
> >   fs/f2fs/file.c | 1 +
> >   1 file changed, 1 insertion(+)
> >
> > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c index
> > ab9844eaa62c..b593e41dbfb3 100644
> > --- a/fs/f2fs/file.c
> > +++ b/fs/f2fs/file.c
> > @@ -1273,6 +1273,7 @@ static int __clone_blkaddrs(struct inode
> *src_inode, struct inode *dst_inode,
> >   				return PTR_ERR(pdst);
> >   			}
> >   			memcpy_page(pdst, 0, psrc, 0, PAGE_SIZE);
> > +			flush_dcache_page(pdst);
> 
> __clone_blkaddrs() was introduced for fallocate() w/
> FALLOC_FL_COLLAPSE_RANGE and FALLOC_FL_INSERT_RANGE cases, they
> are both covered w/ invalidate_lock, and before __clone_blkaddrs(), it
> will call truncate_pagecache() to drop all mapping of pagecache, so it's
> safe here?
> 
> Instead, in f2fs_move_file_range(), we need to cover
> __exchange_data_block() w/ invalidate_lock and drop pagecache as well
> as fallocate() does?

Yes ,it seems has the problem. I test it just now through the POC( ioctl(fd1, F2FS_IOC_MOVE_RANGE, &arg). I read the old data before dropping the cache. It refreshes the source file data after manually dropping cache. I will propose a new patch to solve this problem.

Thanks,

> 
> Thanks,
> 
> >   			set_page_dirty(pdst);
> >   			f2fs_put_page(pdst, 1);
> >   			f2fs_put_page(psrc, 1);

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