Message-ID: <997BA7A9-9DAD-46D2-BDB8-B5EE20971E21@intel.com>
Date:	Thu, 9 Jun 2016 08:59:09 +0000
From:	"Dilger, Andreas" <andreas.dilger@...el.com>
To:	James Simmons <jsimmons@...radead.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"devel@...verdev.osuosl.org" <devel@...verdev.osuosl.org>,
	"Drokin, Oleg" <oleg.drokin@...el.com>
CC:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"Lustre Development List" <lustre-devel@...ts.lustre.org>
Subject: Re: [PATCH] staging: lustre: llite: remove lloop device

On 2016/06/08, 16:50, "James Simmons" <jsimmons@...radead.org> wrote:

>The lloop device was original developed to work around
>the lack of direct I/O for the default loop back device.
>Also the lloop device greatly out performed the default
>loop back device. The lloop hasn't been worked on for
>some time and now it no longer out performs the loop
>device and loop now supports direct I/O. Since this is
>the case we can delete this device.
>
>Signed-off-by: James Simmons <jsimmons@...radead.org>

Reviewed-by: Andreas Dilger <andreas.dilger@...el.com>

Cheers, Andreas

>---
> drivers/staging/lustre/lustre/Kconfig        |    6 -
> drivers/staging/lustre/lustre/llite/Makefile |    3 -
> drivers/staging/lustre/lustre/llite/lloop.c  |  883 --------------------------
> 3 files changed, 0 insertions(+), 892 deletions(-)
> delete mode 100644 drivers/staging/lustre/lustre/llite/lloop.c
>
>diff --git a/drivers/staging/lustre/lustre/Kconfig b/drivers/staging/lustre/lustre/Kconfig
>index 8ac7cd4..9f5d75f 100644
>--- a/drivers/staging/lustre/lustre/Kconfig
>+++ b/drivers/staging/lustre/lustre/Kconfig
>@@ -54,9 +54,3 @@ config LUSTRE_TRANSLATE_ERRNOS
> 	bool
> 	depends on LUSTRE_FS && !X86
> 	default y
>-
>-config LUSTRE_LLITE_LLOOP
>-	tristate "Lustre virtual block device"
>-	depends on LUSTRE_FS && BLOCK
>-	depends on !PPC_64K_PAGES && !ARM64_64K_PAGES && !MICROBLAZE_64K_PAGES && !PAGE_SIZE_64KB && !IA64_PAGE_SIZE_64KB && !PARISC_PAGE_SIZE_64KB
>-	default m
>diff --git a/drivers/staging/lustre/lustre/llite/Makefile b/drivers/staging/lustre/lustre/llite/Makefile
>index 2ce10ff..19701e7 100644
>--- a/drivers/staging/lustre/lustre/llite/Makefile
>+++ b/drivers/staging/lustre/lustre/llite/Makefile
>@@ -1,5 +1,4 @@
> obj-$(CONFIG_LUSTRE_FS) += lustre.o
>-obj-$(CONFIG_LUSTRE_LLITE_LLOOP) += llite_lloop.o
> lustre-y := dcache.o dir.o file.o llite_close.o llite_lib.o llite_nfs.o \
> 	    rw.o namei.o symlink.o llite_mmap.o \
> 	    xattr.o xattr_cache.o remote_perm.o llite_rmtacl.o \
>@@ -7,5 +6,3 @@ lustre-y := dcache.o dir.o file.o llite_close.o llite_lib.o llite_nfs.o \
> 	    glimpse.o lcommon_cl.o lcommon_misc.o \
> 	    vvp_dev.o vvp_page.o vvp_lock.o vvp_io.o vvp_object.o vvp_req.o \
> 	    lproc_llite.o
>-
>-llite_lloop-y := lloop.o
>diff --git a/drivers/staging/lustre/lustre/llite/lloop.c b/drivers/staging/lustre/lustre/llite/lloop.c
>deleted file mode 100644
>index 813a9a3..0000000
>--- a/drivers/staging/lustre/lustre/llite/lloop.c
>+++ /dev/null
>@@ -1,883 +0,0 @@
>-/*
>- * GPL HEADER START
>- *
>- * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
>- *
>- * This program is free software; you can redistribute it and/or modify
>- * it under the terms of the GNU General Public License version 2 only,
>- * as published by the Free Software Foundation.
>- *
>- * This program is distributed in the hope that it will be useful, but
>- * WITHOUT ANY WARRANTY; without even the implied warranty of
>- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>- * General Public License version 2 for more details (a copy is included
>- * in the LICENSE file that accompanied this code).
>- *
>- * You should have received a copy of the GNU General Public License
>- * version 2 along with this program; If not, see
>- * http://www.sun.com/software/products/lustre/docs/GPLv2.pdf
>- *
>- * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
>- * CA 95054 USA or visit www.sun.com if you need additional information or
>- * have any questions.
>- *
>- * GPL HEADER END
>- */
>-/*
>- * Copyright (c) 2007, 2010, Oracle and/or its affiliates. All rights reserved.
>- * Use is subject to license terms.
>- *
>- * Copyright (c) 2011, 2012, Intel Corporation.
>- */
>-/*
>- * This file is part of Lustre, http://www.lustre.org/
>- * Lustre is a trademark of Sun Microsystems, Inc.
>- */
>-
>-/*
>- *  linux/drivers/block/loop.c
>- *
>- *  Written by Theodore Ts'o, 3/29/93
>- *
>- * Copyright 1993 by Theodore Ts'o.  Redistribution of this file is
>- * permitted under the GNU General Public License.
>- *
>- * Modularized and updated for 1.1.16 kernel - Mitch Dsouza 28th May 1994
>- * Adapted for 1.3.59 kernel - Andries Brouwer, 1 Feb 1996
>- *
>- * Fixed do_loop_request() re-entrancy - Vincent.Renardias@....com Mar 20, 1997
>- *
>- * Added devfs support - Richard Gooch <rgooch@...f.csiro.au> 16-Jan-1998
>- *
>- * Handle sparse backing files correctly - Kenn Humborg, Jun 28, 1998
>- *
>- * Loadable modules and other fixes by AK, 1998
>- *
>- * Maximum number of loop devices now dynamic via max_loop module parameter.
>- * Russell Kroll <rkroll@...loits.org> 19990701
>- *
>- * Maximum number of loop devices when compiled-in now selectable by passing
>- * max_loop=<1-255> to the kernel on boot.
>- * Erik I. Bols?, <eriki@...olde.no>, Oct 31, 1999
>- *
>- * Completely rewrite request handling to be make_request_fn style and
>- * non blocking, pushing work to a helper thread. Lots of fixes from
>- * Al Viro too.
>- * Jens Axboe <axboe@...e.de>, Nov 2000
>- *
>- * Support up to 256 loop devices
>- * Heinz Mauelshagen <mge@...tina.com>, Feb 2002
>- *
>- * Support for falling back on the write file operation when the address space
>- * operations prepare_write and/or commit_write are not available on the
>- * backing filesystem.
>- * Anton Altaparmakov, 16 Feb 2005
>- *
>- * Still To Fix:
>- * - Advisory locking is ignored here.
>- * - Should use an own CAP_* category instead of CAP_SYS_ADMIN
>- *
>- */
>-
>-#include <linux/module.h>
>-
>-#include <linux/sched.h>
>-#include <linux/fs.h>
>-#include <linux/file.h>
>-#include <linux/stat.h>
>-#include <linux/errno.h>
>-#include <linux/major.h>
>-#include <linux/wait.h>
>-#include <linux/blkdev.h>
>-#include <linux/blkpg.h>
>-#include <linux/init.h>
>-#include <linux/swap.h>
>-#include <linux/slab.h>
>-#include <linux/suspend.h>
>-#include <linux/writeback.h>
>-#include <linux/buffer_head.h>		/* for invalidate_bdev() */
>-#include <linux/completion.h>
>-#include <linux/highmem.h>
>-#include <linux/gfp.h>
>-#include <linux/pagevec.h>
>-#include <linux/uaccess.h>
>-
>-#include "../include/lustre_lib.h"
>-#include "../include/lustre_lite.h"
>-#include "llite_internal.h"
>-
>-#define LLOOP_MAX_SEGMENTS	LNET_MAX_IOV
>-
>-/* Possible states of device */
>-enum {
>-	LLOOP_UNBOUND,
>-	LLOOP_BOUND,
>-	LLOOP_RUNDOWN,
>-};
>-
>-struct lloop_device {
>-	int		  lo_number;
>-	int		  lo_refcnt;
>-	loff_t	       lo_offset;
>-	loff_t	       lo_sizelimit;
>-	int		  lo_flags;
>-	struct file	 *lo_backing_file;
>-	struct block_device *lo_device;
>-	unsigned	     lo_blocksize;
>-
>-	gfp_t		  old_gfp_mask;
>-
>-	spinlock_t		lo_lock;
>-	struct bio		*lo_bio;
>-	struct bio		*lo_biotail;
>-	int			lo_state;
>-	struct semaphore	lo_sem;
>-	struct mutex		lo_ctl_mutex;
>-	atomic_t	 lo_pending;
>-	wait_queue_head_t	  lo_bh_wait;
>-
>-	struct request_queue *lo_queue;
>-
>-	const struct lu_env *lo_env;
>-	struct cl_io	 lo_io;
>-	struct ll_dio_pages  lo_pvec;
>-
>-	/* data to handle bio for lustre. */
>-	struct lo_request_data {
>-		struct page *lrd_pages[LLOOP_MAX_SEGMENTS];
>-		loff_t       lrd_offsets[LLOOP_MAX_SEGMENTS];
>-	} lo_requests[1];
>-};
>-
>-/*
>- * Loop flags
>- */
>-enum {
>-	LO_FLAGS_READ_ONLY       = 1,
>-};
>-
>-static int lloop_major;
>-#define MAX_LOOP_DEFAULT  16
>-static int max_loop = MAX_LOOP_DEFAULT;
>-static struct lloop_device *loop_dev;
>-static struct gendisk **disks;
>-static struct mutex lloop_mutex;
>-static void *ll_iocontrol_magic;
>-
>-static loff_t get_loop_size(struct lloop_device *lo, struct file *file)
>-{
>-	loff_t size, offset, loopsize;
>-
>-	/* Compute loopsize in bytes */
>-	size = i_size_read(file->f_mapping->host);
>-	offset = lo->lo_offset;
>-	loopsize = size - offset;
>-	if (lo->lo_sizelimit > 0 && lo->lo_sizelimit < loopsize)
>-		loopsize = lo->lo_sizelimit;
>-
>-	/*
>-	 * Unfortunately, if we want to do I/O on the device,
>-	 * the number of 512-byte sectors has to fit into a sector_t.
>-	 */
>-	return loopsize >> 9;
>-}
>-
>-static int do_bio_lustrebacked(struct lloop_device *lo, struct bio *head)
>-{
>-	const struct lu_env  *env   = lo->lo_env;
>-	struct cl_io	 *io    = &lo->lo_io;
>-	struct inode	 *inode = file_inode(lo->lo_backing_file);
>-	struct cl_object     *obj = ll_i2info(inode)->lli_clob;
>-	pgoff_t	       offset;
>-	int		   ret;
>-	int		   rw;
>-	u32		   page_count = 0;
>-	struct bio_vec       bvec;
>-	struct bvec_iter   iter;
>-	struct bio	   *bio;
>-	ssize_t	       bytes;
>-
>-	struct ll_dio_pages  *pvec = &lo->lo_pvec;
>-	struct page	 **pages = pvec->ldp_pages;
>-	loff_t	       *offsets = pvec->ldp_offsets;
>-
>-	truncate_inode_pages(inode->i_mapping, 0);
>-
>-	/* initialize the IO */
>-	memset(io, 0, sizeof(*io));
>-	io->ci_obj = obj;
>-	ret = cl_io_init(env, io, CIT_MISC, obj);
>-	if (ret)
>-		return io->ci_result;
>-	io->ci_lockreq = CILR_NEVER;
>-
>-	rw = head->bi_rw;
>-	for (bio = head; bio ; bio = bio->bi_next) {
>-		LASSERT(rw == bio->bi_rw);
>-
>-		offset = (pgoff_t)(bio->bi_iter.bi_sector << 9) + lo->lo_offset;
>-		bio_for_each_segment(bvec, bio, iter) {
>-			BUG_ON(bvec.bv_offset != 0);
>-			BUG_ON(bvec.bv_len != PAGE_SIZE);
>-
>-			pages[page_count] = bvec.bv_page;
>-			offsets[page_count] = offset;
>-			page_count++;
>-			offset += bvec.bv_len;
>-		}
>-		LASSERT(page_count <= LLOOP_MAX_SEGMENTS);
>-	}
>-
>-	ll_stats_ops_tally(ll_i2sbi(inode),
>-			(rw == WRITE) ? LPROC_LL_BRW_WRITE : LPROC_LL_BRW_READ,
>-			page_count);
>-
>-	pvec->ldp_size = page_count << PAGE_SHIFT;
>-	pvec->ldp_nr = page_count;
>-
>-	/* FIXME: in ll_direct_rw_pages, it has to allocate many cl_page{}s to
>-	 * write those pages into OST. Even worse case is that more pages
>-	 * would be asked to write out to swap space, and then finally get here
>-	 * again.
>-	 * Unfortunately this is NOT easy to fix.
>-	 * Thoughts on solution:
>-	 * 0. Define a reserved pool for cl_pages, which could be a list of
>-	 *    pre-allocated cl_pages;
>-	 * 1. Define a new operation in cl_object_operations{}, says clo_depth,
>-	 *    which measures how many layers for this lustre object. Generally
>-	 *    speaking, the depth would be 2, one for llite, and one for lovsub.
>-	 *    However, for SNS, there will be more since we need additional page
>-	 *    to store parity;
>-	 * 2. Reserve the # of (page_count * depth) cl_pages from the reserved
>-	 *    pool. Afterwards, the clio would allocate the pages from reserved
>-	 *    pool, this guarantees we needn't allocate the cl_pages from
>-	 *    generic cl_page slab cache.
>-	 *    Of course, if there is NOT enough pages in the pool, we might
>-	 *    be asked to write less pages once, this purely depends on
>-	 *    implementation. Anyway, we should be careful to avoid deadlocking.
>-	 */
>-	inode_lock(inode);
>-	bytes = ll_direct_rw_pages(env, io, rw, inode, pvec);
>-	inode_unlock(inode);
>-	cl_io_fini(env, io);
>-	return (bytes == pvec->ldp_size) ? 0 : (int)bytes;
>-}
>-
>-/*
>- * Add bio to back of pending list
>- */
>-static void loop_add_bio(struct lloop_device *lo, struct bio *bio)
>-{
>-	unsigned long flags;
>-
>-	spin_lock_irqsave(&lo->lo_lock, flags);
>-	if (lo->lo_biotail) {
>-		lo->lo_biotail->bi_next = bio;
>-		lo->lo_biotail = bio;
>-	} else {
>-		lo->lo_bio = lo->lo_biotail = bio;
>-	}
>-	spin_unlock_irqrestore(&lo->lo_lock, flags);
>-
>-	atomic_inc(&lo->lo_pending);
>-	if (waitqueue_active(&lo->lo_bh_wait))
>-		wake_up(&lo->lo_bh_wait);
>-}
>-
>-/*
>- * Grab first pending buffer
>- */
>-static unsigned int loop_get_bio(struct lloop_device *lo, struct bio **req)
>-{
>-	struct bio *first;
>-	struct bio **bio;
>-	unsigned int count = 0;
>-	unsigned int page_count = 0;
>-	int rw;
>-
>-	spin_lock_irq(&lo->lo_lock);
>-	first = lo->lo_bio;
>-	if (unlikely(!first)) {
>-		spin_unlock_irq(&lo->lo_lock);
>-		return 0;
>-	}
>-
>-	/* TODO: need to split the bio, too bad. */
>-	LASSERT(first->bi_vcnt <= LLOOP_MAX_SEGMENTS);
>-
>-	rw = first->bi_rw;
>-	bio = &lo->lo_bio;
>-	while (*bio && (*bio)->bi_rw == rw) {
>-		CDEBUG(D_INFO, "bio sector %llu size %u count %u vcnt%u\n",
>-		       (unsigned long long)(*bio)->bi_iter.bi_sector,
>-		       (*bio)->bi_iter.bi_size,
>-		       page_count, (*bio)->bi_vcnt);
>-		if (page_count + (*bio)->bi_vcnt > LLOOP_MAX_SEGMENTS)
>-			break;
>-
>-		page_count += (*bio)->bi_vcnt;
>-		count++;
>-		bio = &(*bio)->bi_next;
>-	}
>-	if (*bio) {
>-		/* Some of bios can't be mergeable. */
>-		lo->lo_bio = *bio;
>-		*bio = NULL;
>-	} else {
>-		/* Hit the end of queue */
>-		lo->lo_biotail = NULL;
>-		lo->lo_bio = NULL;
>-	}
>-	*req = first;
>-	spin_unlock_irq(&lo->lo_lock);
>-	return count;
>-}
>-
>-static blk_qc_t loop_make_request(struct request_queue *q, struct bio *old_bio)
>-{
>-	struct lloop_device *lo = q->queuedata;
>-	int rw = bio_rw(old_bio);
>-	int inactive;
>-
>-	blk_queue_split(q, &old_bio, q->bio_split);
>-
>-	if (!lo)
>-		goto err;
>-
>-	CDEBUG(D_INFO, "submit bio sector %llu size %u\n",
>-	       (unsigned long long)old_bio->bi_iter.bi_sector,
>-	       old_bio->bi_iter.bi_size);
>-
>-	spin_lock_irq(&lo->lo_lock);
>-	inactive = lo->lo_state != LLOOP_BOUND;
>-	spin_unlock_irq(&lo->lo_lock);
>-	if (inactive)
>-		goto err;
>-
>-	if (rw == WRITE) {
>-		if (lo->lo_flags & LO_FLAGS_READ_ONLY)
>-			goto err;
>-	} else if (rw == READA) {
>-		rw = READ;
>-	} else if (rw != READ) {
>-		CERROR("lloop: unknown command (%x)\n", rw);
>-		goto err;
>-	}
>-	loop_add_bio(lo, old_bio);
>-	return BLK_QC_T_NONE;
>-err:
>-	bio_io_error(old_bio);
>-	return BLK_QC_T_NONE;
>-}
>-
>-static inline void loop_handle_bio(struct lloop_device *lo, struct bio *bio)
>-{
>-	int ret;
>-
>-	ret = do_bio_lustrebacked(lo, bio);
>-	while (bio) {
>-		struct bio *tmp = bio->bi_next;
>-
>-		bio->bi_next = NULL;
>-		bio->bi_error = ret;
>-		bio_endio(bio);
>-		bio = tmp;
>-	}
>-}
>-
>-static inline int loop_active(struct lloop_device *lo)
>-{
>-	return atomic_read(&lo->lo_pending) ||
>-		(lo->lo_state == LLOOP_RUNDOWN);
>-}
>-
>-/*
>- * worker thread that handles reads/writes to file backed loop devices,
>- * to avoid blocking in our make_request_fn.
>- */
>-static int loop_thread(void *data)
>-{
>-	struct lloop_device *lo = data;
>-	struct bio *bio;
>-	unsigned int count;
>-	unsigned long times = 0;
>-	unsigned long total_count = 0;
>-
>-	struct lu_env *env;
>-	int refcheck;
>-	int ret = 0;
>-
>-	set_user_nice(current, MIN_NICE);
>-
>-	lo->lo_state = LLOOP_BOUND;
>-
>-	env = cl_env_get(&refcheck);
>-	if (IS_ERR(env)) {
>-		ret = PTR_ERR(env);
>-		goto out;
>-	}
>-
>-	lo->lo_env = env;
>-	memset(&lo->lo_pvec, 0, sizeof(lo->lo_pvec));
>-	lo->lo_pvec.ldp_pages   = lo->lo_requests[0].lrd_pages;
>-	lo->lo_pvec.ldp_offsets = lo->lo_requests[0].lrd_offsets;
>-
>-	/*
>-	 * up sem, we are running
>-	 */
>-	up(&lo->lo_sem);
>-
>-	for (;;) {
>-		wait_event(lo->lo_bh_wait, loop_active(lo));
>-		if (!atomic_read(&lo->lo_pending)) {
>-			int exiting = 0;
>-
>-			spin_lock_irq(&lo->lo_lock);
>-			exiting = (lo->lo_state == LLOOP_RUNDOWN);
>-			spin_unlock_irq(&lo->lo_lock);
>-			if (exiting)
>-				break;
>-		}
>-
>-		bio = NULL;
>-		count = loop_get_bio(lo, &bio);
>-		if (!count) {
>-			CWARN("lloop(minor: %d): missing bio\n", lo->lo_number);
>-			continue;
>-		}
>-
>-		total_count += count;
>-		if (total_count < count) {     /* overflow */
>-			total_count = count;
>-			times = 1;
>-		} else {
>-			times++;
>-		}
>-		if ((times & 127) == 0) {
>-			CDEBUG(D_INFO, "total: %lu, count: %lu, avg: %lu\n",
>-			       total_count, times, total_count / times);
>-		}
>-
>-		LASSERT(bio);
>-		LASSERT(count <= atomic_read(&lo->lo_pending));
>-		loop_handle_bio(lo, bio);
>-		atomic_sub(count, &lo->lo_pending);
>-	}
>-	cl_env_put(env, &refcheck);
>-
>-out:
>-	up(&lo->lo_sem);
>-	return ret;
>-}
>-
>-static int loop_set_fd(struct lloop_device *lo, struct file *unused,
>-		       struct block_device *bdev, struct file *file)
>-{
>-	struct inode	 *inode;
>-	struct address_space *mapping;
>-	int		   lo_flags = 0;
>-	int		   error;
>-	loff_t		size;
>-
>-	if (!try_module_get(THIS_MODULE))
>-		return -ENODEV;
>-
>-	error = -EBUSY;
>-	if (lo->lo_state != LLOOP_UNBOUND)
>-		goto out;
>-
>-	mapping = file->f_mapping;
>-	inode = mapping->host;
>-
>-	error = -EINVAL;
>-	if (!S_ISREG(inode->i_mode) || inode->i_sb->s_magic != LL_SUPER_MAGIC)
>-		goto out;
>-
>-	if (!(file->f_mode & FMODE_WRITE))
>-		lo_flags |= LO_FLAGS_READ_ONLY;
>-
>-	size = get_loop_size(lo, file);
>-
>-	if ((loff_t)(sector_t)size != size) {
>-		error = -EFBIG;
>-		goto out;
>-	}
>-
>-	/* remove all pages in cache so as dirty pages not to be existent. */
>-	truncate_inode_pages(mapping, 0);
>-
>-	set_device_ro(bdev, (lo_flags & LO_FLAGS_READ_ONLY) != 0);
>-
>-	lo->lo_blocksize = PAGE_SIZE;
>-	lo->lo_device = bdev;
>-	lo->lo_flags = lo_flags;
>-	lo->lo_backing_file = file;
>-	lo->lo_sizelimit = 0;
>-	lo->old_gfp_mask = mapping_gfp_mask(mapping);
>-	mapping_set_gfp_mask(mapping, lo->old_gfp_mask & ~(__GFP_IO|__GFP_FS));
>-
>-	lo->lo_bio = lo->lo_biotail = NULL;
>-
>-	/*
>-	 * set queue make_request_fn, and add limits based on lower level
>-	 * device
>-	 */
>-	blk_queue_make_request(lo->lo_queue, loop_make_request);
>-	lo->lo_queue->queuedata = lo;
>-
>-	/* queue parameters */
>-	CLASSERT(PAGE_SIZE < (1 << (sizeof(unsigned short) * 8)));
>-	blk_queue_logical_block_size(lo->lo_queue,
>-				     (unsigned short)PAGE_SIZE);
>-	blk_queue_max_hw_sectors(lo->lo_queue,
>-				 LLOOP_MAX_SEGMENTS << (PAGE_SHIFT - 9));
>-	blk_queue_max_segments(lo->lo_queue, LLOOP_MAX_SEGMENTS);
>-
>-	set_capacity(disks[lo->lo_number], size);
>-	bd_set_size(bdev, size << 9);
>-
>-	set_blocksize(bdev, lo->lo_blocksize);
>-
>-	kthread_run(loop_thread, lo, "lloop%d", lo->lo_number);
>-	down(&lo->lo_sem);
>-	return 0;
>-
>-out:
>-	/* This is safe: open() is still holding a reference. */
>-	module_put(THIS_MODULE);
>-	return error;
>-}
>-
>-static int loop_clr_fd(struct lloop_device *lo, struct block_device *bdev,
>-		       int count)
>-{
>-	struct file *filp = lo->lo_backing_file;
>-	gfp_t gfp = lo->old_gfp_mask;
>-
>-	if (lo->lo_state != LLOOP_BOUND)
>-		return -ENXIO;
>-
>-	if (lo->lo_refcnt > count)	/* we needed one fd for the ioctl */
>-		return -EBUSY;
>-
>-	if (!filp)
>-		return -EINVAL;
>-
>-	spin_lock_irq(&lo->lo_lock);
>-	lo->lo_state = LLOOP_RUNDOWN;
>-	spin_unlock_irq(&lo->lo_lock);
>-	wake_up(&lo->lo_bh_wait);
>-
>-	down(&lo->lo_sem);
>-	lo->lo_backing_file = NULL;
>-	lo->lo_device = NULL;
>-	lo->lo_offset = 0;
>-	lo->lo_sizelimit = 0;
>-	lo->lo_flags = 0;
>-	invalidate_bdev(bdev);
>-	set_capacity(disks[lo->lo_number], 0);
>-	bd_set_size(bdev, 0);
>-	mapping_set_gfp_mask(filp->f_mapping, gfp);
>-	lo->lo_state = LLOOP_UNBOUND;
>-	fput(filp);
>-	/* This is safe: open() is still holding a reference. */
>-	module_put(THIS_MODULE);
>-	return 0;
>-}
>-
>-static int lo_open(struct block_device *bdev, fmode_t mode)
>-{
>-	struct lloop_device *lo = bdev->bd_disk->private_data;
>-
>-	mutex_lock(&lo->lo_ctl_mutex);
>-	lo->lo_refcnt++;
>-	mutex_unlock(&lo->lo_ctl_mutex);
>-
>-	return 0;
>-}
>-
>-static void lo_release(struct gendisk *disk, fmode_t mode)
>-{
>-	struct lloop_device *lo = disk->private_data;
>-
>-	mutex_lock(&lo->lo_ctl_mutex);
>-	--lo->lo_refcnt;
>-	mutex_unlock(&lo->lo_ctl_mutex);
>-}
>-
>-/* lloop device node's ioctl function. */
>-static int lo_ioctl(struct block_device *bdev, fmode_t mode,
>-		    unsigned int cmd, unsigned long arg)
>-{
>-	struct lloop_device *lo = bdev->bd_disk->private_data;
>-	struct inode *inode = NULL;
>-	int err = 0;
>-
>-	mutex_lock(&lloop_mutex);
>-	switch (cmd) {
>-	case LL_IOC_LLOOP_DETACH: {
>-		err = loop_clr_fd(lo, bdev, 2);
>-		if (err == 0)
>-			blkdev_put(bdev, 0); /* grabbed in LLOOP_ATTACH */
>-		break;
>-	}
>-
>-	case LL_IOC_LLOOP_INFO: {
>-		struct lu_fid fid;
>-
>-		if (!lo->lo_backing_file) {
>-			err = -ENOENT;
>-			break;
>-		}
>-		if (!inode)
>-			inode = file_inode(lo->lo_backing_file);
>-		if (lo->lo_state == LLOOP_BOUND)
>-			fid = ll_i2info(inode)->lli_fid;
>-		else
>-			fid_zero(&fid);
>-
>-		if (copy_to_user((void __user *)arg, &fid, sizeof(fid)))
>-			err = -EFAULT;
>-		break;
>-	}
>-
>-	default:
>-		err = -EINVAL;
>-		break;
>-	}
>-	mutex_unlock(&lloop_mutex);
>-
>-	return err;
>-}
>-
>-static struct block_device_operations lo_fops = {
>-	.owner =	THIS_MODULE,
>-	.open =	 lo_open,
>-	.release =      lo_release,
>-	.ioctl =	lo_ioctl,
>-};
>-
>-/* dynamic iocontrol callback.
>- * This callback is registered in lloop_init and will be called by
>- * ll_iocontrol_call.
>- *
>- * This is a llite regular file ioctl function. It takes the responsibility
>- * of attaching or detaching a file by a lloop's device number.
>- */
>-static enum llioc_iter lloop_ioctl(struct inode *unused, struct file *file,
>-				   unsigned int cmd, unsigned long arg,
>-				   void *magic, int *rcp)
>-{
>-	struct lloop_device *lo = NULL;
>-	struct block_device *bdev = NULL;
>-	int err = 0;
>-	dev_t dev;
>-
>-	if (magic != ll_iocontrol_magic)
>-		return LLIOC_CONT;
>-
>-	if (!disks) {
>-		err = -ENODEV;
>-		goto out1;
>-	}
>-
>-	CWARN("Enter llop_ioctl\n");
>-
>-	mutex_lock(&lloop_mutex);
>-	switch (cmd) {
>-	case LL_IOC_LLOOP_ATTACH: {
>-		struct lloop_device *lo_free = NULL;
>-		int i;
>-
>-		for (i = 0; i < max_loop; i++, lo = NULL) {
>-			lo = &loop_dev[i];
>-			if (lo->lo_state == LLOOP_UNBOUND) {
>-				if (!lo_free)
>-					lo_free = lo;
>-				continue;
>-			}
>-			if (file_inode(lo->lo_backing_file) == file_inode(file))
>-				break;
>-		}
>-		if (lo || !lo_free) {
>-			err = -EBUSY;
>-			goto out;
>-		}
>-
>-		lo = lo_free;
>-		dev = MKDEV(lloop_major, lo->lo_number);
>-
>-		/* quit if the used pointer is writable */
>-		if (put_user((long)old_encode_dev(dev), (long __user *)arg)) {
>-			err = -EFAULT;
>-			goto out;
>-		}
>-
>-		bdev = blkdev_get_by_dev(dev, file->f_mode, NULL);
>-		if (IS_ERR(bdev)) {
>-			err = PTR_ERR(bdev);
>-			goto out;
>-		}
>-
>-		get_file(file);
>-		err = loop_set_fd(lo, NULL, bdev, file);
>-		if (err) {
>-			fput(file);
>-			blkdev_put(bdev, 0);
>-		}
>-
>-		break;
>-	}
>-
>-	case LL_IOC_LLOOP_DETACH_BYDEV: {
>-		int minor;
>-
>-		dev = old_decode_dev(arg);
>-		if (MAJOR(dev) != lloop_major) {
>-			err = -EINVAL;
>-			goto out;
>-		}
>-
>-		minor = MINOR(dev);
>-		if (minor > max_loop - 1) {
>-			err = -EINVAL;
>-			goto out;
>-		}
>-
>-		lo = &loop_dev[minor];
>-		if (lo->lo_state != LLOOP_BOUND) {
>-			err = -EINVAL;
>-			goto out;
>-		}
>-
>-		bdev = lo->lo_device;
>-		err = loop_clr_fd(lo, bdev, 1);
>-		if (err == 0)
>-			blkdev_put(bdev, 0); /* grabbed in LLOOP_ATTACH */
>-
>-		break;
>-	}
>-
>-	default:
>-		err = -EINVAL;
>-		break;
>-	}
>-
>-out:
>-	mutex_unlock(&lloop_mutex);
>-out1:
>-	if (rcp)
>-		*rcp = err;
>-	return LLIOC_STOP;
>-}
>-
>-static int __init lloop_init(void)
>-{
>-	int	i;
>-	unsigned int cmdlist[] = {
>-		LL_IOC_LLOOP_ATTACH,
>-		LL_IOC_LLOOP_DETACH_BYDEV,
>-	};
>-
>-	if (max_loop < 1 || max_loop > 256) {
>-		max_loop = MAX_LOOP_DEFAULT;
>-		CWARN("lloop: invalid max_loop (must be between 1 and 256), using default (%u)\n",
>-		      max_loop);
>-	}
>-
>-	lloop_major = register_blkdev(0, "lloop");
>-	if (lloop_major < 0)
>-		return -EIO;
>-
>-	CDEBUG(D_CONFIG, "registered lloop major %d with %u minors\n",
>-	       lloop_major, max_loop);
>-
>-	ll_iocontrol_magic = ll_iocontrol_register(lloop_ioctl, 2, cmdlist);
>-	if (!ll_iocontrol_magic)
>-		goto out_mem1;
>-
>-	loop_dev = kcalloc(max_loop, sizeof(*loop_dev), GFP_KERNEL);
>-	if (!loop_dev)
>-		goto out_mem1;
>-
>-	disks = kcalloc(max_loop, sizeof(*disks), GFP_KERNEL);
>-	if (!disks)
>-		goto out_mem2;
>-
>-	for (i = 0; i < max_loop; i++) {
>-		disks[i] = alloc_disk(1);
>-		if (!disks[i])
>-			goto out_mem3;
>-	}
>-
>-	mutex_init(&lloop_mutex);
>-
>-	for (i = 0; i < max_loop; i++) {
>-		struct lloop_device *lo = &loop_dev[i];
>-		struct gendisk *disk = disks[i];
>-
>-		lo->lo_queue = blk_alloc_queue(GFP_KERNEL);
>-		if (!lo->lo_queue)
>-			goto out_mem4;
>-
>-		mutex_init(&lo->lo_ctl_mutex);
>-		sema_init(&lo->lo_sem, 0);
>-		init_waitqueue_head(&lo->lo_bh_wait);
>-		lo->lo_number = i;
>-		spin_lock_init(&lo->lo_lock);
>-		disk->major = lloop_major;
>-		disk->first_minor = i;
>-		disk->fops = &lo_fops;
>-		sprintf(disk->disk_name, "lloop%d", i);
>-		disk->private_data = lo;
>-		disk->queue = lo->lo_queue;
>-	}
>-
>-	/* We cannot fail after we call this, so another loop!*/
>-	for (i = 0; i < max_loop; i++)
>-		add_disk(disks[i]);
>-	return 0;
>-
>-out_mem4:
>-	while (i--)
>-		blk_cleanup_queue(loop_dev[i].lo_queue);
>-	i = max_loop;
>-out_mem3:
>-	while (i--)
>-		put_disk(disks[i]);
>-	kfree(disks);
>-out_mem2:
>-	kfree(loop_dev);
>-out_mem1:
>-	unregister_blkdev(lloop_major, "lloop");
>-	ll_iocontrol_unregister(ll_iocontrol_magic);
>-	CERROR("lloop: ran out of memory\n");
>-	return -ENOMEM;
>-}
>-
>-static void lloop_exit(void)
>-{
>-	int i;
>-
>-	ll_iocontrol_unregister(ll_iocontrol_magic);
>-	for (i = 0; i < max_loop; i++) {
>-		del_gendisk(disks[i]);
>-		blk_cleanup_queue(loop_dev[i].lo_queue);
>-		put_disk(disks[i]);
>-	}
>-
>-	unregister_blkdev(lloop_major, "lloop");
>-
>-	kfree(disks);
>-	kfree(loop_dev);
>-}
>-
>-module_param(max_loop, int, 0444);
>-MODULE_PARM_DESC(max_loop, "maximum of lloop_device");
>-MODULE_AUTHOR("OpenSFS, Inc. <http://www.lustre.org/>");
>-MODULE_DESCRIPTION("Lustre virtual block device");
>-MODULE_VERSION(LUSTRE_VERSION_STRING);
>-MODULE_LICENSE("GPL");
>-
>-module_init(lloop_init);
>-module_exit(lloop_exit);
>-- 
>1.7.1
>
>

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