[XFS] Block on unwritten extent conversion during synchronous direct I/O.
Currently we do not wait on extent conversion to occur, and hence we can return to userspace from a synchronous direct I/O write without having completed all the actions in the write. Hence a read after the write may see zeroes (unwritten extent) rather than the data that was written. Block the I/O completion by triggering a synchronous workqueue flush to ensure that the conversion has occurred before we return to userspace. SGI-PV: 964092 SGI-Modid: xfs-linux-melb:xfs-kern:28775a Signed-off-by: David Chinner <dgc@sgi.com> Signed-off-by: Tim Shimmin <tes@sgi.com>
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@ -108,14 +108,19 @@ xfs_page_trace(
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/*
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* Schedule IO completion handling on a xfsdatad if this was
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* the final hold on this ioend.
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* the final hold on this ioend. If we are asked to wait,
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* flush the workqueue.
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*/
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STATIC void
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xfs_finish_ioend(
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xfs_ioend_t *ioend)
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xfs_ioend_t *ioend,
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int wait)
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{
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if (atomic_dec_and_test(&ioend->io_remaining))
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if (atomic_dec_and_test(&ioend->io_remaining)) {
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queue_work(xfsdatad_workqueue, &ioend->io_work);
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if (wait)
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flush_workqueue(xfsdatad_workqueue);
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}
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}
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/*
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@ -334,7 +339,7 @@ xfs_end_bio(
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bio->bi_end_io = NULL;
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bio_put(bio);
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xfs_finish_ioend(ioend);
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xfs_finish_ioend(ioend, 0);
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return 0;
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}
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@ -470,7 +475,7 @@ xfs_submit_ioend(
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}
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if (bio)
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xfs_submit_ioend_bio(ioend, bio);
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xfs_finish_ioend(ioend);
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xfs_finish_ioend(ioend, 0);
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} while ((ioend = next) != NULL);
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}
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@ -1416,6 +1421,13 @@ xfs_end_io_direct(
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* This is not necessary for synchronous direct I/O, but we do
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* it anyway to keep the code uniform and simpler.
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*
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* Well, if only it were that simple. Because synchronous direct I/O
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* requires extent conversion to occur *before* we return to userspace,
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* we have to wait for extent conversion to complete. Look at the
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* iocb that has been passed to us to determine if this is AIO or
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* not. If it is synchronous, tell xfs_finish_ioend() to kick the
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* workqueue and wait for it to complete.
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*
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* The core direct I/O code might be changed to always call the
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* completion handler in the future, in which case all this can
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* go away.
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@ -1423,9 +1435,9 @@ xfs_end_io_direct(
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ioend->io_offset = offset;
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ioend->io_size = size;
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if (ioend->io_type == IOMAP_READ) {
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xfs_finish_ioend(ioend);
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xfs_finish_ioend(ioend, 0);
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} else if (private && size > 0) {
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xfs_finish_ioend(ioend);
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xfs_finish_ioend(ioend, is_sync_kiocb(iocb));
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} else {
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/*
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* A direct I/O write ioend starts it's life in unwritten
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@ -1434,7 +1446,7 @@ xfs_end_io_direct(
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* handler.
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*/
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INIT_WORK(&ioend->io_work, xfs_end_bio_written);
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xfs_finish_ioend(ioend);
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xfs_finish_ioend(ioend, 0);
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}
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/*
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