xfs_buf.c

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/*
 * Copyright (c) 2000-2004 Silicon Graphics, Inc.  All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of version 2 of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 *
 * Further, this software is distributed without any warranty that it is
 * free of the rightful claim of any third person regarding infringement
 * or the like.  Any license provided herein, whether implied or
 * otherwise, applies only to this software file.  Patent licenses, if
 * any, provided herein do not apply to combinations of this program with
 * other software, or any other product whatsoever.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write the Free Software Foundation, Inc., 59
 * Temple Place - Suite 330, Boston MA 02111-1307, USA.
 *
 * Contact information: Silicon Graphics, Inc., 1600 Amphitheatre Pkwy,
 * Mountain View, CA  94043, or:
 *
 * http://www.sgi.com
 *
 * For further information regarding this notice, see:
 *
 * http://oss.sgi.com/projects/GenInfo/SGIGPLNoticeExplan/
 */

/*
 *	The xfs_buf.c code provides an abstract buffer cache model on top
 *	of the Linux page cache.  Cached metadata blocks for a file system
 *	are hashed to the inode for the block device.  xfs_buf.c assembles
 *	buffers (xfs_buf_t) on demand to aggregate such cached pages for I/O.
 *
 *      Written by Steve Lord, Jim Mostek, Russell Cattelan
 *		    and Rajagopal Ananthanarayanan ("ananth") at SGI.
 *
 */

#include <linux/stddef.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/pagemap.h>
#include <linux/init.h>
#include <linux/vmalloc.h>
#include <linux/bio.h>
#include <linux/sysctl.h>
#include <linux/proc_fs.h>
#include <linux/workqueue.h>
#include <linux/suspend.h>
#include <linux/percpu.h>

#include "xfs_linux.h"

#ifndef GFP_READAHEAD
#define GFP_READAHEAD	(__GFP_NOWARN|__GFP_NORETRY)
#endif

/*
 * File wide globals
 */

STATIC kmem_cache_t *pagebuf_cache;
STATIC kmem_shaker_t pagebuf_shake;
STATIC int pagebuf_daemon_wakeup(int, unsigned int);
STATIC void pagebuf_delwri_queue(xfs_buf_t *, int);
STATIC struct workqueue_struct *pagebuf_logio_workqueue;
STATIC struct workqueue_struct *pagebuf_dataio_workqueue;

/*
 * Pagebuf debugging
 */

#ifdef PAGEBUF_TRACE
void
pagebuf_trace(
	xfs_buf_t	*pb,
	char		*id,
	void		*data,
	void		*ra)
{
	ktrace_enter(pagebuf_trace_buf,
		pb, id,
		(void *)(unsigned long)pb->pb_flags,
		(void *)(unsigned long)pb->pb_hold.counter,
		(void *)(unsigned long)pb->pb_sema.count.counter,
		(void *)current,
		data, ra,
		(void *)(unsigned long)((pb->pb_file_offset>>32) & 0xffffffff),
		(void *)(unsigned long)(pb->pb_file_offset & 0xffffffff),
		(void *)(unsigned long)pb->pb_buffer_length,
		NULL, NULL, NULL, NULL, NULL);
}
ktrace_t *pagebuf_trace_buf;
#define PAGEBUF_TRACE_SIZE	4096
#define PB_TRACE(pb, id, data)	\
	pagebuf_trace(pb, id, (void *)data, (void *)__builtin_return_address(0))
#else
#define PB_TRACE(pb, id, data)	do { } while (0)
#endif

#ifdef PAGEBUF_LOCK_TRACKING
# define PB_SET_OWNER(pb)	((pb)->pb_last_holder = current->pid)
# define PB_CLEAR_OWNER(pb)	((pb)->pb_last_holder = -1)
# define PB_GET_OWNER(pb)	((pb)->pb_last_holder)
#else
# define PB_SET_OWNER(pb)	do { } while (0)
# define PB_CLEAR_OWNER(pb)	do { } while (0)
# define PB_GET_OWNER(pb)	do { } while (0)
#endif

/*
 * Pagebuf allocation / freeing.
 */

#define pb_to_gfp(flags) \
	(((flags) & PBF_READ_AHEAD) ? GFP_READAHEAD : \
	 ((flags) & PBF_DONT_BLOCK) ? GFP_NOFS : GFP_KERNEL)

#define pb_to_km(flags) \
	 (((flags) & PBF_DONT_BLOCK) ? KM_NOFS : KM_SLEEP)


#define pagebuf_allocate(flags) \
	kmem_zone_alloc(pagebuf_cache, pb_to_km(flags))
#define pagebuf_deallocate(pb) \
	kmem_zone_free(pagebuf_cache, (pb));

/*
 * Pagebuf hashing
 */

#define NBITS	8
#define NHASH	(1<<NBITS)

typedef struct {
	struct list_head	pb_hash;
	spinlock_t		pb_hash_lock;
} pb_hash_t;

STATIC pb_hash_t	pbhash[NHASH];
#define pb_hash(pb)	&pbhash[pb->pb_hash_index]

STATIC int
_bhash(
	struct block_device *bdev,
	loff_t		base)
{
	int		bit, hval;

	base >>= 9;
	base ^= (unsigned long)bdev / L1_CACHE_BYTES;
	for (bit = hval = 0; base && bit < sizeof(base) * 8; bit += NBITS) {
		hval ^= (int)base & (NHASH-1);
		base >>= NBITS;
	}
	return hval;
}

/*
 * Mapping of multi-page buffers into contiguous virtual space
 */

typedef struct a_list {
	void		*vm_addr;
	struct a_list	*next;
} a_list_t;

STATIC a_list_t		*as_free_head;
STATIC int		as_list_len;
STATIC spinlock_t	as_lock = SPIN_LOCK_UNLOCKED;

/*
 * Try to batch vunmaps because they are costly.
 */
STATIC void
free_address(
	void		*addr)
{
	a_list_t	*aentry;

	aentry = kmalloc(sizeof(a_list_t), GFP_ATOMIC);
	if (aentry) {
		spin_lock(&as_lock);
		aentry->next = as_free_head;
		aentry->vm_addr = addr;
		as_free_head = aentry;
		as_list_len++;
		spin_unlock(&as_lock);
	} else {
		vunmap(addr);
	}
}

STATIC void
purge_addresses(void)
{
	a_list_t	*aentry, *old;

	if (as_free_head == NULL)
		return;

	spin_lock(&as_lock);
	aentry = as_free_head;
	as_free_head = NULL;
	as_list_len = 0;
	spin_unlock(&as_lock);

	while ((old = aentry) != NULL) {
		vunmap(aentry->vm_addr);
		aentry = aentry->next;
		kfree(old);
	}
}

/*
 *	Internal pagebuf object manipulation
 */

STATIC void
_pagebuf_initialize(
	xfs_buf_t		*pb,
	xfs_buftarg_t		*target,
	loff_t			range_base,
	size_t			range_length,
	page_buf_flags_t	flags)
{
	/*
	 * We don't want certain flags to appear in pb->pb_flags.
	 */
	flags &= ~(PBF_LOCK|PBF_MAPPED|PBF_DONT_BLOCK|PBF_READ_AHEAD);

	memset(pb, 0, sizeof(xfs_buf_t));
	atomic_set(&pb->pb_hold, 1);
	init_MUTEX_LOCKED(&pb->pb_iodonesema);
	INIT_LIST_HEAD(&pb->pb_list);
	INIT_LIST_HEAD(&pb->pb_hash_list);
	init_MUTEX_LOCKED(&pb->pb_sema); /* held, no waiters */
	PB_SET_OWNER(pb);
	pb->pb_target = target;
	pb->pb_file_offset = range_base;
	/*
	 * Set buffer_length and count_desired to the same value initially.
	 * I/O routines should use count_desired, which will be the same in
	 * most cases but may be reset (e.g. XFS recovery).
	 */
	pb->pb_buffer_length = pb->pb_count_desired = range_length;
	pb->pb_flags = flags | PBF_NONE;
	pb->pb_bn = XFS_BUF_DADDR_NULL;
	atomic_set(&pb->pb_pin_count, 0);
	init_waitqueue_head(&pb->pb_waiters);

	XFS_STATS_INC(pb_create);
	PB_TRACE(pb, "initialize", target);
}

/*
 * Allocate a page array capable of holding a specified number
 * of pages, and point the page buf at it.
 */
STATIC int
_pagebuf_get_pages(
	xfs_buf_t		*pb,
	int			page_count,
	page_buf_flags_t	flags)
{
	/* Make sure that we have a page list */
	if (pb->pb_pages == NULL) {
		pb->pb_offset = page_buf_poff(pb->pb_file_offset);
		pb->pb_page_count = page_count;
		if (page_count <= PB_PAGES) {
			pb->pb_pages = pb->pb_page_array;
		} else {
			pb->pb_pages = kmem_alloc(sizeof(struct page *) *
					page_count, pb_to_km(flags));
			if (pb->pb_pages == NULL)
				return -ENOMEM;
		}
		memset(pb->pb_pages, 0, sizeof(struct page *) * page_count);
	}
	return 0;
}

/*
 *	Frees pb_pages if it was malloced.
 */
STATIC void
_pagebuf_free_pages(
	xfs_buf_t	*bp)
{
	if (bp->pb_pages != bp->pb_page_array) {
		kmem_free(bp->pb_pages,
			  bp->pb_page_count * sizeof(struct page *));
	}
}

/*
 *	Releases the specified buffer.
 *
 * 	The modification state of any associated pages is left unchanged.
 * 	The buffer most not be on any hash - use pagebuf_rele instead for
 * 	hashed and refcounted buffers
 */
void
pagebuf_free(
	xfs_buf_t		*bp)
{
	PB_TRACE(bp, "free", 0);

	ASSERT(list_empty(&bp->pb_hash_list));

	if (bp->pb_flags & _PBF_PAGE_CACHE) {
		uint		i;

		if ((bp->pb_flags & PBF_MAPPED) && (bp->pb_page_count > 1))
			free_address(bp->pb_addr - bp->pb_offset);

		for (i = 0; i < bp->pb_page_count; i++)
			page_cache_release(bp->pb_pages[i]);
		_pagebuf_free_pages(bp);
	} else if (bp->pb_flags & _PBF_KMEM_ALLOC) {
		 /*
		  * XXX(hch): bp->pb_count_desired might be incorrect (see
		  * pagebuf_associate_memory for details), but fortunately
		  * the Linux version of kmem_free ignores the len argument..
		  */
		kmem_free(bp->pb_addr, bp->pb_count_desired);
		_pagebuf_free_pages(bp);
	}

	pagebuf_deallocate(bp);
}

/*
 *	Finds all pages for buffer in question and builds it's page list.
 */
STATIC int
_pagebuf_lookup_pages(
	xfs_buf_t		*bp,
	uint			flags)
{
	struct address_space	*mapping = bp->pb_target->pbr_mapping;
	unsigned int		sectorshift = bp->pb_target->pbr_sshift;
	size_t			blocksize = bp->pb_target->pbr_bsize;
	size_t			size = bp->pb_count_desired;
	size_t			nbytes, offset;
	int			gfp_mask = pb_to_gfp(flags);
	unsigned short		page_count, i;
	pgoff_t			first;
	loff_t			end;
	int			error;

	end = bp->pb_file_offset + bp->pb_buffer_length;
	page_count = page_buf_btoc(end) - page_buf_btoct(bp->pb_file_offset);

	error = _pagebuf_get_pages(bp, page_count, flags);
	if (unlikely(error))
		return error;
	bp->pb_flags |= _PBF_PAGE_CACHE;

	offset = bp->pb_offset;
	first = bp->pb_file_offset >> PAGE_CACHE_SHIFT;

	for (i = 0; i < bp->pb_page_count; i++) {
		struct page	*page;
		uint		retries = 0;

	      retry:
		page = find_or_create_page(mapping, first + i, gfp_mask);
		if (unlikely(page == NULL)) {
			if (flags & PBF_READ_AHEAD) {
				bp->pb_page_count = i;
				for (i = 0; i < bp->pb_page_count; i++)
					unlock_page(bp->pb_pages[i]);
				return -ENOMEM;
			}

			/*
			 * This could deadlock.
			 *
			 * But until all the XFS lowlevel code is revamped to
			 * handle buffer allocation failures we can't do much.
			 */
			if (!(++retries % 100))
				printk(KERN_ERR
					"possible deadlock in %s (mode:0x%x)\n",
					__FUNCTION__, gfp_mask);

			XFS_STATS_INC(pb_page_retries);
			pagebuf_daemon_wakeup(0, gfp_mask);
			set_current_state(TASK_UNINTERRUPTIBLE);
			schedule_timeout(10);
			goto retry;
		}

		XFS_STATS_INC(pb_page_found);

		nbytes = min_t(size_t, size, PAGE_CACHE_SIZE - offset);
		size -= nbytes;

		if (!PageUptodate(page)) {
			page_count--;
			if (blocksize == PAGE_CACHE_SIZE) {
				if (flags & PBF_READ)
					bp->pb_locked = 1;
			} else if (!PagePrivate(page)) {
				unsigned long	j, range;

				/*
				 * In this case page->private holds a bitmap
				 * of uptodate sectors within the page
				 */
				ASSERT(blocksize < PAGE_CACHE_SIZE);
				range = (offset + nbytes) >> sectorshift;
				for (j = offset >> sectorshift; j < range; j++)
					if (!test_bit(j, &page->private))
						break;
				if (j == range)
					page_count++;
			}
		}

		bp->pb_pages[i] = page;
		offset = 0;
	}

	if (!bp->pb_locked) {
		for (i = 0; i < bp->pb_page_count; i++)
			unlock_page(bp->pb_pages[i]);
	}

	if (page_count) {
		/* if we have any uptodate pages, mark that in the buffer */
		bp->pb_flags &= ~PBF_NONE;

		/* if some pages aren't uptodate, mark that in the buffer */
		if (page_count != bp->pb_page_count)
			bp->pb_flags |= PBF_PARTIAL;
	}

	PB_TRACE(bp, "lookup_pages", (long)page_count);
	return error;
}

/*
 *	Map buffer into kernel address-space if nessecary.
 */
STATIC int
_pagebuf_map_pages(
	xfs_buf_t		*bp,
	uint			flags)
{
	/* A single page buffer is always mappable */
	if (bp->pb_page_count == 1) {
		bp->pb_addr = page_address(bp->pb_pages[0]) + bp->pb_offset;
		bp->pb_flags |= PBF_MAPPED;
	} else if (flags & PBF_MAPPED) {
		if (as_list_len > 64)
			purge_addresses();
		bp->pb_addr = vmap(bp->pb_pages, bp->pb_page_count,
				VM_MAP, PAGE_KERNEL);
		if (unlikely(bp->pb_addr == NULL))
			return -ENOMEM;
		bp->pb_addr += bp->pb_offset;
		bp->pb_flags |= PBF_MAPPED;
	}

	return 0;
}

/*
 *	Finding and Reading Buffers
 */

/*
 *	_pagebuf_find
 *
 *	Looks up, and creates if absent, a lockable buffer for
 *	a given range of an inode.  The buffer is returned
 *	locked.	 If other overlapping buffers exist, they are
 *	released before the new buffer is created and locked,
 *	which may imply that this call will block until those buffers
 *	are unlocked.  No I/O is implied by this call.
 */
STATIC xfs_buf_t *
_pagebuf_find(				/* find buffer for block	*/
	xfs_buftarg_t		*target,/* target for block		*/
	loff_t			ioff,	/* starting offset of range	*/
	size_t			isize,	/* length of range		*/
	page_buf_flags_t	flags,	/* PBF_TRYLOCK			*/
	xfs_buf_t		*new_pb)/* newly allocated buffer	*/
{
	loff_t			range_base;
	size_t			range_length;
	int			hval;
	pb_hash_t		*h;
	xfs_buf_t		*pb, *n;
	int			not_locked;

	range_base = (ioff << BBSHIFT);
	range_length = (isize << BBSHIFT);

	/* Ensure we never do IOs smaller than the sector size */
	BUG_ON(range_length < (1 << target->pbr_sshift));

	/* Ensure we never do IOs that are not sector aligned */
	BUG_ON(range_base & (loff_t)target->pbr_smask);

	hval = _bhash(target->pbr_bdev, range_base);
	h = &pbhash[hval];

	spin_lock(&h->pb_hash_lock);
	list_for_each_entry_safe(pb, n, &h->pb_hash, pb_hash_list) {
		if (pb->pb_target == target &&
		    pb->pb_file_offset == range_base &&
		    pb->pb_buffer_length == range_length) {
			/* If we look at something bring it to the
			 * front of the list for next time
			 */
			atomic_inc(&pb->pb_hold);
			list_move(&pb->pb_hash_list, &h->pb_hash);
			goto found;
		}
	}

	/* No match found */
	if (new_pb) {
		_pagebuf_initialize(new_pb, target, range_base,
				range_length, flags);
		new_pb->pb_hash_index = hval;
		list_add(&new_pb->pb_hash_list, &h->pb_hash);
	} else {
		XFS_STATS_INC(pb_miss_locked);
	}

	spin_unlock(&h->pb_hash_lock);
	return (new_pb);

found:
	spin_unlock(&h->pb_hash_lock);

	/* Attempt to get the semaphore without sleeping,
	 * if this does not work then we need to drop the
	 * spinlock and do a hard attempt on the semaphore.
	 */
	not_locked = down_trylock(&pb->pb_sema);
	if (not_locked) {
		if (!(flags & PBF_TRYLOCK)) {
			/* wait for buffer ownership */
			PB_TRACE(pb, "get_lock", 0);
			pagebuf_lock(pb);
			XFS_STATS_INC(pb_get_locked_waited);
		} else {
			/* We asked for a trylock and failed, no need
			 * to look at file offset and length here, we
			 * know that this pagebuf at least overlaps our
			 * pagebuf and is locked, therefore our buffer
			 * either does not exist, or is this buffer
			 */

			pagebuf_rele(pb);
			XFS_STATS_INC(pb_busy_locked);
			return (NULL);
		}
	} else {
		/* trylock worked */
		PB_SET_OWNER(pb);
	}

	if (pb->pb_flags & PBF_STALE)
		pb->pb_flags &= PBF_MAPPED;
	PB_TRACE(pb, "got_lock", 0);
	XFS_STATS_INC(pb_get_locked);
	return (pb);
}


/*
 *	pagebuf_find
 *
 *	pagebuf_find returns a buffer matching the specified range of
 *	data for the specified target, if any of the relevant blocks
 *	are in memory.  The buffer may have unallocated holes, if
 *	some, but not all, of the blocks are in memory.  Even where
 *	pages are present in the buffer, not all of every page may be
 *	valid.
 */
xfs_buf_t *
pagebuf_find(				/* find buffer for block	*/
					/* if the block is in memory	*/
	xfs_buftarg_t		*target,/* target for block		*/
	loff_t			ioff,	/* starting offset of range	*/
	size_t			isize,	/* length of range		*/
	page_buf_flags_t	flags)	/* PBF_TRYLOCK			*/
{
	return _pagebuf_find(target, ioff, isize, flags, NULL);
}

/*
 *	pagebuf_get
 *
 *	pagebuf_get assembles a buffer covering the specified range.
 *	Some or all of the blocks in the range may be valid.  Storage
 *	in memory for all portions of the buffer will be allocated,
 *	although backing storage may not be.  If PBF_READ is set in
 *	flags, pagebuf_iostart is called also.
 */
xfs_buf_t *
pagebuf_get(				/* allocate a buffer		*/