Messages in this thread | | | Date | Mon, 30 Jun 2008 16:47:23 +0800 | From | "Zhao Forrest" <> | Subject | Re: Should a block device enforce block atomicity? |
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> > Don't forget that all IO requests are queued on the device. With a > modern HW and disk you usually have NCQ and most drives will throw > away write request to the same sector if they see a later write to > the same sector in the queue. > > That said. There is nothing wrong with writing again and again to > the same sector on disk. File/record locking is done at the FileSystem > level. An application that wants exclusive write need to open the file > that way. Other wise it could even be written from another machine not > even another thread. > > What is it you are concerned with? > I happen to read the email and have a question, that may not be Erez's real question :) Let's suppose the following example: 1 pdflush find a dirty inode and decides to flush a set of dirty pages to harddrive 2 while this set of dirty pages is being committed to harddrive(dma_mapping is done, but dirty pages are not really written to disk media), application/FS is trying to update some pages in this set of dirty pages.
Then what happens? Will application be put into sleep until page flushing to disk media is done?
Thanks, Forrest
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