On Tue, Jan 23, 2024 at 10:36:14AM +0800, Zhihao Cheng wrote:
在 2024/1/22 22:40, Matthew Wilcox 写道:
On Mon, Jan 22, 2024 at 03:22:45PM +0800, Zhihao Cheng wrote:
在 2024/1/21 7:08, Matthew Wilcox (Oracle) 写道:
Page cache reads are lockless, so setting the freshly allocated page uptodate before we've overwritten it with the data it's supposed to have in it will allow a simultaneous reader to see old data. Move the call to SetPageUptodate into ubifs_write_end(), which is after we copied the new data into the page.
This solution looks good to me, and I think 'SetPageUptodate' should be removed from write_begin_slow(slow path) too.
I didn't bother because we have just read into the page so it is uptodate. A racing read will see the data from before the write, but that's an acceptable ordering of events. .
I can't find where the page is read and set uptodate. I think the uninitialized data can be found in following path:
You're right; thanks. I'd misread the code. I'll send a new version in a few hours.