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Commit b32f4c7e authored by Nicholas Bellinger's avatar Nicholas Bellinger
Browse files

target/file: Re-enable optional fd_buffered_io=1 operation 



This patch re-adds the ability to optionally run in buffered FILEIO mode
(eg: w/o O_DSYNC) for device backends in order to once again use the
Linux buffered cache as a write-back storage mechanism.

This logic was originally dropped with mainline v3.5-rc commit:

commit a4dff304
Author: Nicholas Bellinger <nab@linux-iscsi.org>
Date:   Wed May 30 16:25:41 2012 -0700

    target/file: Use O_DSYNC by default for FILEIO backends

This difference with this patch is that fd_create_virtdevice() now
forces the explicit setting of emulate_write_cache=1 when buffered FILEIO
operation has been enabled.

(v2: Switch to FDBD_HAS_BUFFERED_IO_WCE + add more detailed
     comment as requested by hch)

Reported-by: default avatarFerry <iscsitmp@bananateam.nl>
Cc: Christoph Hellwig <hch@lst.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
parent f25590f3

drivers/target/target_core_file.c

+38 −3
Original line number Diff line number Diff line
@@ -125,6 +125,19 @@ static struct se_device *fd_create_virtdevice( 
	 * of pure timestamp updates.

	 */

	flags = O_RDWR | O_CREAT | O_LARGEFILE | O_DSYNC;

	/*

	 * Optionally allow fd_buffered_io=1 to be enabled for people

	 * who want use the fs buffer cache as an WriteCache mechanism.

	 *

	 * This means that in event of a hard failure, there is a risk

	 * of silent data-loss if the SCSI client has *not* performed a

	 * forced unit access (FUA) write, or issued SYNCHRONIZE_CACHE

	 * to write-out the entire device cache.

	 */

	if (fd_dev->fbd_flags & FDBD_HAS_BUFFERED_IO_WCE) {

		pr_debug("FILEIO: Disabling O_DSYNC, using buffered FILEIO\n");

		flags &= ~O_DSYNC;

	}



	file = filp_open(fd_dev->fd_dev_name, flags, 0600);

	if (IS_ERR(file)) {
@@ -188,6 +201,12 @@ static struct se_device *fd_create_virtdevice( 
	if (!dev)

		goto fail;



	if (fd_dev->fbd_flags & FDBD_HAS_BUFFERED_IO_WCE) {

		pr_debug("FILEIO: Forcing setting of emulate_write_cache=1"

			" with FDBD_HAS_BUFFERED_IO_WCE\n");

		dev->se_sub_dev->se_dev_attrib.emulate_write_cache = 1;

	}



	fd_dev->fd_dev_id = fd_host->fd_host_dev_id_count++;

	fd_dev->fd_queue_depth = dev->queue_depth;
@@ -407,6 +426,7 @@ enum { 
static match_table_t tokens = {

	{Opt_fd_dev_name, "fd_dev_name=%s"},

	{Opt_fd_dev_size, "fd_dev_size=%s"},

	{Opt_fd_buffered_io, "fd_buffered_io=%d"},

	{Opt_err, NULL}

};
@@ -418,7 +438,7 @@ static ssize_t fd_set_configfs_dev_params( 
	struct fd_dev *fd_dev = se_dev->se_dev_su_ptr;

	char *orig, *ptr, *arg_p, *opts;

	substring_t args[MAX_OPT_ARGS];

	int ret = 0, token;

	int ret = 0, arg, token;



	opts = kstrdup(page, GFP_KERNEL);

	if (!opts)
@@ -459,6 +479,19 @@ static ssize_t fd_set_configfs_dev_params( 
					" bytes\n", fd_dev->fd_dev_size);

			fd_dev->fbd_flags |= FBDF_HAS_SIZE;

			break;

		case Opt_fd_buffered_io:

			match_int(args, &arg);

			if (arg != 1) {

				pr_err("bogus fd_buffered_io=%d value\n", arg);

				ret = -EINVAL;

				goto out;

			}



			pr_debug("FILEIO: Using buffered I/O"

				" operations for struct fd_dev\n");



			fd_dev->fbd_flags |= FDBD_HAS_BUFFERED_IO_WCE;

			break;

		default:

			break;

		}
@@ -490,8 +523,10 @@ static ssize_t fd_show_configfs_dev_params( 
	ssize_t bl = 0;



	bl = sprintf(b + bl, "TCM FILEIO ID: %u", fd_dev->fd_dev_id);

	bl += sprintf(b + bl, "        File: %s  Size: %llu  Mode: O_DSYNC\n",

		fd_dev->fd_dev_name, fd_dev->fd_dev_size);

	bl += sprintf(b + bl, "        File: %s  Size: %llu  Mode: %s\n",

		fd_dev->fd_dev_name, fd_dev->fd_dev_size,

		(fd_dev->fbd_flags & FDBD_HAS_BUFFERED_IO_WCE) ?

		"Buffered-WCE" : "O_DSYNC");

	return bl;

}

drivers/target/target_core_file.h

+1 −0
Original line number Diff line number Diff line
@@ -14,6 +14,7 @@ 


#define FBDF_HAS_PATH		0x01

#define FBDF_HAS_SIZE		0x02

#define FDBD_HAS_BUFFERED_IO_WCE 0x04



struct fd_dev {

	u32		fbd_flags;