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iomap: Support partial direct I/O on user copy failures
commit 97308f8b0d
upstream
In iomap_dio_rw, when iomap_apply returns an -EFAULT error and the
IOMAP_DIO_PARTIAL flag is set, complete the request synchronously and
return a partial result. This allows the caller to deal with the page
fault and retry the remainder of the request.
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit
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2 changed files with 13 additions and 0 deletions
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@ -581,6 +581,12 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
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if (iov_iter_rw(iter) == READ && iomi.pos >= dio->i_size)
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iov_iter_revert(iter, iomi.pos - dio->i_size);
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if (ret == -EFAULT && dio->size && (dio_flags & IOMAP_DIO_PARTIAL)) {
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if (!(iocb->ki_flags & IOCB_NOWAIT))
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wait_for_completion = true;
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ret = 0;
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}
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/* magic error code to fall back to buffered I/O */
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if (ret == -ENOTBLK) {
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wait_for_completion = true;
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@ -330,6 +330,13 @@ struct iomap_dio_ops {
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*/
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#define IOMAP_DIO_OVERWRITE_ONLY (1 << 1)
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/*
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* When a page fault occurs, return a partial synchronous result and allow
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* the caller to retry the rest of the operation after dealing with the page
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* fault.
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*/
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#define IOMAP_DIO_PARTIAL (1 << 2)
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ssize_t iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
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const struct iomap_ops *ops, const struct iomap_dio_ops *dops,
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unsigned int dio_flags);
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