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teach iomap_dio_rw() to suppress dsync
New flag, equivalent to removal of IOCB_DSYNC from iocb flags. This mimics what btrfs is doing (and that's what btrfs will switch to). However, I'm not at all sure that we want to suppress REQ_FUA for those - all btrfs hack really cares about is suppression of generic_write_sync(). For now let's keep the existing behaviour, but I really want to hear more detailed arguments pro or contra. [folded brain fix from willy] Suggested-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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0e3c3b901c
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2 changed files with 17 additions and 9 deletions
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@ -548,17 +548,19 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
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}
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}
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/* for data sync or sync, we need sync completion processing */
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/* for data sync or sync, we need sync completion processing */
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if (iocb->ki_flags & IOCB_DSYNC)
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if (iocb->ki_flags & IOCB_DSYNC &&
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!(dio_flags & IOMAP_DIO_NOSYNC)) {
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dio->flags |= IOMAP_DIO_NEED_SYNC;
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dio->flags |= IOMAP_DIO_NEED_SYNC;
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/*
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/*
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* For datasync only writes, we optimistically try using FUA for
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* For datasync only writes, we optimistically try
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* this IO. Any non-FUA write that occurs will clear this flag,
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* using FUA for this IO. Any non-FUA write that
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* hence we know before completion whether a cache flush is
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* occurs will clear this flag, hence we know before
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* necessary.
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* completion whether a cache flush is necessary.
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*/
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*/
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if ((iocb->ki_flags & (IOCB_DSYNC | IOCB_SYNC)) == IOCB_DSYNC)
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if (!(iocb->ki_flags & IOCB_SYNC))
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dio->flags |= IOMAP_DIO_WRITE_FUA;
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dio->flags |= IOMAP_DIO_WRITE_FUA;
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}
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}
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}
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if (dio_flags & IOMAP_DIO_OVERWRITE_ONLY) {
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if (dio_flags & IOMAP_DIO_OVERWRITE_ONLY) {
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@ -353,6 +353,12 @@ struct iomap_dio_ops {
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*/
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*/
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#define IOMAP_DIO_PARTIAL (1 << 2)
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#define IOMAP_DIO_PARTIAL (1 << 2)
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/*
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* The caller will sync the write if needed; do not sync it within
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* iomap_dio_rw. Overrides IOMAP_DIO_FORCE_WAIT.
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*/
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#define IOMAP_DIO_NOSYNC (1 << 3)
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ssize_t iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
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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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const struct iomap_ops *ops, const struct iomap_dio_ops *dops,
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unsigned int dio_flags, void *private, size_t done_before);
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unsigned int dio_flags, void *private, size_t done_before);
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