Messages in this thread | | | Date | Mon, 02 Nov 2015 13:05:32 +0200 | From | Boaz Harrosh <> | Subject | Re: [PATCH] osd fs: __r4w_get_page rely on PageUptodate for uptodate |
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On 11/02/2015 01:39 AM, Hugh Dickins wrote: <> >> This patch is not correct! > > I think you have actually confirmed that the patch is correct: > why bother to test PageDirty or PageWriteback when PageUptodate > already tells you what you need? > > Or do these filesystems do something unusual with PageUptodate > when PageDirty is set? I didn't find it. >
This is kind of delicate stuff. It took me a while to get it right when I did it. I don't remember all the details.
But consider this option:
exofs_write_begin on a full PAGE_CACHE_SIZE, the page is instantiated new in page-cache is that PageUptodate(page) then? I thought not. (exofs does not set that)
Now that page I do not want to read in. The latest data is in memory. (Same when this page is in writeback, dirty-bit is cleared)
So for sure if page is dirty or writeback then we surly do not need a read. only if not then we need to consider the PageUptodate(page) state.
Do you think the code is actually wrong as is?
BTW: Very similar code is in fs/nfs/objlayout/objio_osd.c::__r4w_get_page
> Thanks, > Hugh > <>
Thanks Boaz
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