Re: [PATCH] f2fs: fix conflict between atomic_write and truncate

[Jaegeuk Kim <jaegeuk@kernel.org>]

Hi,

On 12/13, Hou Pengyang wrote:
> On 2016/12/13 3:18, Jaegeuk Kim wrote:
> > Hi Pengyang,
> >
> Hi, kim,
> > On 12/12, Hou Pengyang wrote:
> >> In fsync_node_pages path, after locking the last_page for setting dirty,
> >> we should check if the page has been truncated. Or there may be a mem leak,
> >> as this dirty last_page will NOT be found in next page-cache travese.
> >>
> >> This patch adds page->mapping checking, and will NOT rewrite the page if
> >> it has been truncated.
> >>
> >> Signed-off-by: Hou Pengyang <houpengyang@huawei.com>
> >> ---
> >>   fs/f2fs/node.c | 5 +++++
> >>   1 file changed, 5 insertions(+)
> >>
> >> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> >> index c1bbfdc..78c5b50 100644
> >> --- a/fs/f2fs/node.c
> >> +++ b/fs/f2fs/node.c
> >> @@ -1410,6 +1410,11 @@ int fsync_node_pages(struct f2fs_sb_info *sbi, struct inode *inode,
> >>   			"Retry to write fsync mark: ino=%u, idx=%lx",
> >>   					ino, last_page->index);
> >>   		lock_page(last_page);
> >
> > We grabbed a reference count for this last_page, and thus, it won't be released.
> > Something that I missed?
> >
> Some path (e.g. shrink) would NOT release the page if we've grabbed it,
> But truncate operation will invalidate the page from page-cache
> regardless of the page reference.

This is a node page, and we guarantee that nobody will truncate them.
Did you hit an issue regarding to this?

Thanks,

> Patch: 0fac558b965 f2fs: make atomic/volatile operation exclusive
> seems fix this issue by adding inode_lock(inode) to avoid conflict
> between atomic/volatile and truncate operation.
> 
> But this patch makes codes more robust.
> 
> Thanks.
> 
> > Thanks,
> >
> >> +		if (unlikely(last_page->mapping != NODE_MAPPING(sbi))) {
> >> +			unlock_page(last_page);
> >> +			f2fs_put_page(last_page, 0);
> >> +			goto out;
> >> +		}
> >>   		f2fs_wait_on_page_writeback(last_page, NODE, true);
> >>   		set_page_dirty(last_page);
> >>   		unlock_page(last_page);
> >> --
> >> 2.10.1
> >>
> >>
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> > .
> >
> 
> 
> 
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