Messages in this thread | | | Date | Fri, 30 Aug 2013 15:33:39 +0400 | From | Maxim Patlasov <> | Subject | Re: [PATCH 2/2] fuse: wait for writeback in fuse_file_fallocate() -v2 |
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08/30/2013 01:13 PM, Miklos Szeredi пишет: > On Thu, Aug 29, 2013 at 6:41 PM, Miklos Szeredi <miklos@szeredi.hu> wrote: >> BTW, isn't it enough to do the filemap_write_and_wait() *plus* the >> fuse_set_nowrite()? > Thought about it a bit and I think this should do fine. > > Any writes before the fallocate will go trough before the fallocate. > i_mutex guarantees that only one instance of fuse_set_nowrite() is > running. Any mmaped writes during the fallocate() will go after the > fallocate request and the page cache truncation and that's fine too. > Page cache is consistent since it doens't contain pages for those > writes to the hole. Subsequent reads to that area will fill them in. > > Any other concerns?
No. What you suggest looks as a neat and correct solution. I'll resend the updated patch after some testing (since now till Monday).
As for proof-of-correctness, all you wrote above is correct, but the first point had been boiling my mind for a while. I came to the following reasoning (hopefully it is what you meant):
The fact that filemap_write_and_wait() returned infers that end_page_writeback() was called for all relevant pages. And fuse doesn't call it before adding request to fi->queued_writes and calling fuse_flush_writepages(). And the latter, in turn, guarantees proper accounting of request in fi->writectr. Here, of course, it's crucial that we can't have concurrent fuse_set_nowrite(), as you explained. Hence, so far as fi->writectr was bumped, fuse_set_nowrite() we call after filemap_write_and_wait() would wait until all changes have gone to the server.
Thanks, Maxim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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