linux-kernel - Re: [GIT PULL] direct IO support for loop driver

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Date:	Thu, 21 Nov 2013 09:34:32 -0800
From:	Christoph Hellwig <hch@...radead.org>
To:	Kent Overstreet <kmo@...erainc.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Dave Kleikamp <dave.kleikamp@...cle.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	"Maxim V. Patlasov" <mpatlasov@...allels.com>, linux-aio@...ck.org,
	Jens Axboe <axboe@...nel.dk>
Subject: Re: [GIT PULL] direct IO support for loop driver

find the target one below.  I haven't found the ecryptfs work, but it
is a lot more involved as it only wants to use direct I/O, not aio.

--- a/drivers/target/target_core_file.c
+++ b/drivers/target/target_core_file.c
@@ -31,6 +31,7 @@
 #include <linux/spinlock.h>
 #include <linux/module.h>
 #include <linux/falloc.h>
+#include <linux/blk_types.h>
 #include <scsi/scsi.h>
 #include <scsi/scsi_host.h>
 #include <asm/unaligned.h>
@@ -120,6 +121,8 @@ static int fd_configure_device(struct se_device *dev)
 	 * of pure timestamp updates.
 	 */
 	flags = O_RDWR | O_CREAT | O_LARGEFILE | O_DSYNC;
+	if (1)
+		flags |= O_DIRECT;
 
 	/*
 	 * Optionally allow fd_buffered_io=1 to be enabled for people
@@ -546,6 +549,61 @@ fd_execute_unmap(struct se_cmd *cmd)
 	return sbc_execute_unmap(cmd, fd_do_unmap, file);
 }
 
+static void fd_rw_aio_complete(u64 data, long res)
+{
+	struct se_cmd *cmd = (struct se_cmd *)(uintptr_t)data;
+
+	kfree(cmd->priv);
+
+	if (res < 0)
+		target_complete_cmd(cmd, SAM_STAT_CHECK_CONDITION);
+	else
+		target_complete_cmd(cmd, SAM_STAT_GOOD);
+}
+
+static sense_reason_t
+fd_rw_aio(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents,
+	      enum dma_data_direction data_direction)
+{
+	struct se_device *se_dev = cmd->se_dev;
+	struct fd_dev *dev = FD_DEV(se_dev);
+	struct file *file = dev->fd_file;
+	struct scatterlist *sg;
+	struct kiocb *iocb;
+	unsigned int op;
+	struct iov_iter iter;
+	struct bio_vec *bvec;
+	loff_t pos = (cmd->t_task_lba * se_dev->dev_attrib.block_size);
+	int i;
+
+	iocb = aio_kernel_alloc(GFP_NOIO);
+	if (!iocb)
+		return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
+	
+	if (data_direction == DMA_TO_DEVICE)
+		op = IOCB_CMD_WRITE_ITER;
+	else
+		op = IOCB_CMD_READ_ITER;
+
+	bvec = cmd->priv = kcalloc(sgl_nents, sizeof(struct bio_vec), GFP_NOIO);
+	if (!bvec) {
+		aio_kernel_free(iocb);
+		return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
+	}
+
+	for_each_sg(sgl, sg, sgl_nents, i) {
+		bvec[i].bv_page = sg_page(sg);
+		bvec[i].bv_len = sg->length;
+		bvec[i].bv_offset = sg->offset;
+	}
+
+	iov_iter_init_bvec(&iter, bvec, sgl_nents, bvec_length(bvec, sgl_nents), 0);
+	aio_kernel_init_rw(iocb, file, iov_iter_count(&iter), pos);
+	aio_kernel_init_callback(iocb, fd_rw_aio_complete, (u64)(uintptr_t)bvec);
+
+	return aio_kernel_submit(iocb, op, &iter);
+}
+
 static sense_reason_t
 fd_execute_rw(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents,
 	      enum dma_data_direction data_direction)
@@ -553,6 +611,9 @@ fd_execute_rw(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents,
 	struct se_device *dev = cmd->se_dev;
 	int ret = 0;
 
+	if (1)
+		return fd_rw_aio(cmd, sgl, sgl_nents, data_direction);
+
 	/*
 	 * Call vectorized fileio functions to map struct scatterlist
 	 * physical memory addresses to struct iovec virtual memory.
--
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