gc.c

linux 内核源代码

/*
 * JFFS2 -- Journalling Flash File System, Version 2.
 *
 * Copyright © 2001-2007 Red Hat, Inc.
 *
 * Created by David Woodhouse <[e-mail]>
 *
 * For licensing information, see the file 'LICENCE' in this directory.
 *
 */

#include <linux/kernel.h>
#include <linux/mtd/mtd.h>
#include <linux/slab.h>
#include <linux/pagemap.h>
#include <linux/crc32.h>
#include <linux/compiler.h>
#include <linux/stat.h>
#include "nodelist.h"
#include "compr.h"

static int jffs2_garbage_collect_pristine(struct jffs2_sb_info *c,
					  struct jffs2_inode_cache *ic,
					  struct jffs2_raw_node_ref *raw);
static int jffs2_garbage_collect_metadata(struct jffs2_sb_info *c, struct jffs2_eraseblock *jeb,
					struct jffs2_inode_info *f, struct jffs2_full_dnode *fd);
static int jffs2_garbage_collect_dirent(struct jffs2_sb_info *c, struct jffs2_eraseblock *jeb,
					struct jffs2_inode_info *f, struct jffs2_full_dirent *fd);
static int jffs2_garbage_collect_deletion_dirent(struct jffs2_sb_info *c, struct jffs2_eraseblock *jeb,
					struct jffs2_inode_info *f, struct jffs2_full_dirent *fd);
static int jffs2_garbage_collect_hole(struct jffs2_sb_info *c, struct jffs2_eraseblock *jeb,
				      struct jffs2_inode_info *f, struct jffs2_full_dnode *fn,
				      uint32_t start, uint32_t end);
static int jffs2_garbage_collect_dnode(struct jffs2_sb_info *c, struct jffs2_eraseblock *jeb,
				       struct jffs2_inode_info *f, struct jffs2_full_dnode *fn,
				       uint32_t start, uint32_t end);
static int jffs2_garbage_collect_live(struct jffs2_sb_info *c,  struct jffs2_eraseblock *jeb,
			       struct jffs2_raw_node_ref *raw, struct jffs2_inode_info *f);

/* Called with erase_completion_lock held */
static struct jffs2_eraseblock *jffs2_find_gc_block(struct jffs2_sb_info *c)
{
	struct jffs2_eraseblock *ret;
	struct list_head *nextlist = NULL;
	int n = jiffies % 128;

	/* Pick an eraseblock to garbage collect next. This is where we'll
	   put the clever wear-levelling algorithms. Eventually.  */
	/* We possibly want to favour the dirtier blocks more when the
	   number of free blocks is low. */
again:
	if (!list_empty(&c->bad_used_list) && c->nr_free_blocks > c->resv_blocks_gcbad) {
		D1(printk(KERN_DEBUG "Picking block from bad_used_list to GC next\n"));
		nextlist = &c->bad_used_list;
	} else if (n < 50 && !list_empty(&c->erasable_list)) {
		/* Note that most of them will have gone directly to be erased.
		   So don't favour the erasable_list _too_ much. */
		D1(printk(KERN_DEBUG "Picking block from erasable_list to GC next\n"));
		nextlist = &c->erasable_list;
	} else if (n < 110 && !list_empty(&c->very_dirty_list)) {
		/* Most of the time, pick one off the very_dirty list */
		D1(printk(KERN_DEBUG "Picking block from very_dirty_list to GC next\n"));
		nextlist = &c->very_dirty_list;
	} else if (n < 126 && !list_empty(&c->dirty_list)) {
		D1(printk(KERN_DEBUG "Picking block from dirty_list to GC next\n"));
		nextlist = &c->dirty_list;
	} else if (!list_empty(&c->clean_list)) {
		D1(printk(KERN_DEBUG "Picking block from clean_list to GC next\n"));
		nextlist = &c->clean_list;
	} else if (!list_empty(&c->dirty_list)) {
		D1(printk(KERN_DEBUG "Picking block from dirty_list to GC next (clean_list was empty)\n"));

		nextlist = &c->dirty_list;
	} else if (!list_empty(&c->very_dirty_list)) {
		D1(printk(KERN_DEBUG "Picking block from very_dirty_list to GC next (clean_list and dirty_list were empty)\n"));
		nextlist = &c->very_dirty_list;
	} else if (!list_empty(&c->erasable_list)) {
		D1(printk(KERN_DEBUG "Picking block from erasable_list to GC next (clean_list and {very_,}dirty_list were empty)\n"));

		nextlist = &c->erasable_list;
	} else if (!list_empty(&c->erasable_pending_wbuf_list)) {
		/* There are blocks are wating for the wbuf sync */
		D1(printk(KERN_DEBUG "Synching wbuf in order to reuse erasable_pending_wbuf_list blocks\n"));
		spin_unlock(&c->erase_completion_lock);
		jffs2_flush_wbuf_pad(c);
		spin_lock(&c->erase_completion_lock);
		goto again;
	} else {
		/* Eep. All were empty */
		D1(printk(KERN_NOTICE "jffs2: No clean, dirty _or_ erasable blocks to GC from! Where are they all?\n"));
		return NULL;
	}

	ret = list_entry(nextlist->next, struct jffs2_eraseblock, list);
	list_del(&ret->list);
	c->gcblock = ret;
	ret->gc_node = ret->first_node;
	if (!ret->gc_node) {
		printk(KERN_WARNING "Eep. ret->gc_node for block at 0x%08x is NULL\n", ret->offset);
		BUG();
	}

	/* Have we accidentally picked a clean block with wasted space ? */
	if (ret->wasted_size) {
		D1(printk(KERN_DEBUG "Converting wasted_size %08x to dirty_size\n", ret->wasted_size));
		ret->dirty_size += ret->wasted_size;
		c->wasted_size -= ret->wasted_size;
		c->dirty_size += ret->wasted_size;
		ret->wasted_size = 0;
	}

	return ret;
}

/* jffs2_garbage_collect_pass
 * Make a single attempt to progress GC. Move one node, and possibly
 * start erasing one eraseblock.
 */
int jffs2_garbage_collect_pass(struct jffs2_sb_info *c)
{
	struct jffs2_inode_info *f;
	struct jffs2_inode_cache *ic;
	struct jffs2_eraseblock *jeb;
	struct jffs2_raw_node_ref *raw;
	uint32_t gcblock_dirty;
	int ret = 0, inum, nlink;
	int xattr = 0;

	if (down_interruptible(&c->alloc_sem))
		return -EINTR;

	for (;;) {
		spin_lock(&c->erase_completion_lock);
		if (!c->unchecked_size)
			break;

		/* We can't start doing GC yet. We haven't finished checking
		   the node CRCs etc. Do it now. */

		/* checked_ino is protected by the alloc_sem */
		if (c->checked_ino > c->highest_ino && xattr) {
			printk(KERN_CRIT "Checked all inodes but still 0x%x bytes of unchecked space?\n",
			       c->unchecked_size);
			jffs2_dbg_dump_block_lists_nolock(c);
			spin_unlock(&c->erase_completion_lock);
			up(&c->alloc_sem);
			return -ENOSPC;
		}

		spin_unlock(&c->erase_completion_lock);

		if (!xattr)
			xattr = jffs2_verify_xattr(c);

		spin_lock(&c->inocache_lock);

		ic = jffs2_get_ino_cache(c, c->checked_ino++);

		if (!ic) {
			spin_unlock(&c->inocache_lock);
			continue;
		}

		if (!ic->nlink) {
			D1(printk(KERN_DEBUG "Skipping check of ino #%d with nlink zero\n",
				  ic->ino));
			spin_unlock(&c->inocache_lock);
			jffs2_xattr_delete_inode(c, ic);
			continue;
		}
		switch(ic->state) {
		case INO_STATE_CHECKEDABSENT:
		case INO_STATE_PRESENT:
			D1(printk(KERN_DEBUG "Skipping ino #%u already checked\n", ic->ino));
			spin_unlock(&c->inocache_lock);
			continue;

		case INO_STATE_GC:
		case INO_STATE_CHECKING:
			printk(KERN_WARNING "Inode #%u is in state %d during CRC check phase!\n", ic->ino, ic->state);
			spin_unlock(&c->inocache_lock);
			BUG();

		case INO_STATE_READING:
			/* We need to wait for it to finish, lest we move on
			   and trigger the BUG() above while we haven't yet
			   finished checking all its nodes */
			D1(printk(KERN_DEBUG "Waiting for ino #%u to finish reading\n", ic->ino));
			/* We need to come back again for the _same_ inode. We've
			 made no progress in this case, but that should be OK */
			c->checked_ino--;

			up(&c->alloc_sem);
			sleep_on_spinunlock(&c->inocache_wq, &c->inocache_lock);
			return 0;

		default:
			BUG();

		case INO_STATE_UNCHECKED:
			;
		}
		ic->state = INO_STATE_CHECKING;
		spin_unlock(&c->inocache_lock);

		D1(printk(KERN_DEBUG "jffs2_garbage_collect_pass() triggering inode scan of ino#%u\n", ic->ino));

		ret = jffs2_do_crccheck_inode(c, ic);
		if (ret)
			printk(KERN_WARNING "Returned error for crccheck of ino #%u. Expect badness...\n", ic->ino);

		jffs2_set_inocache_state(c, ic, INO_STATE_CHECKEDABSENT);
		up(&c->alloc_sem);
		return ret;
	}

	/* First, work out which block we're garbage-collecting */
	jeb = c->gcblock;

	if (!jeb)
		jeb = jffs2_find_gc_block(c);

	if (!jeb) {
		D1 (printk(KERN_NOTICE "jffs2: Couldn't find erase block to garbage collect!\n"));
		spin_unlock(&c->erase_completion_lock);
		up(&c->alloc_sem);
		return -EIO;
	}

	D1(printk(KERN_DEBUG "GC from block %08x, used_size %08x, dirty_size %08x, free_size %08x\n", jeb->offset, jeb->used_size, jeb->dirty_size, jeb->free_size));
	D1(if (c->nextblock)
	   printk(KERN_DEBUG "Nextblock at  %08x, used_size %08x, dirty_size %08x, wasted_size %08x, free_size %08x\n", c->nextblock->offset, c->nextblock->used_size, c->nextblock->dirty_size, c->nextblock->wasted_size, c->nextblock->free_size));

	if (!jeb->used_size) {
		up(&c->alloc_sem);
		goto eraseit;
	}

	raw = jeb->gc_node;
	gcblock_dirty = jeb->dirty_size;

	while(ref_obsolete(raw)) {
		D1(printk(KERN_DEBUG "Node at 0x%08x is obsolete... skipping\n", ref_offset(raw)));
		raw = ref_next(raw);
		if (unlikely(!raw)) {
			printk(KERN_WARNING "eep. End of raw list while still supposedly nodes to GC\n");
			printk(KERN_WARNING "erase block at 0x%08x. free_size 0x%08x, dirty_size 0x%08x, used_size 0x%08x\n",
			       jeb->offset, jeb->free_size, jeb->dirty_size, jeb->used_size);
			jeb->gc_node = raw;
			spin_unlock(&c->erase_completion_lock);
			up(&c->alloc_sem);
			BUG();
		}
	}
	jeb->gc_node = raw;

	D1(printk(KERN_DEBUG "Going to garbage collect node at 0x%08x\n", ref_offset(raw)));

	if (!raw->next_in_ino) {
		/* Inode-less node. Clean marker, snapshot or something like that */
		spin_unlock(&c->erase_completion_lock);
		if (ref_flags(raw) == REF_PRISTINE) {
			/* It's an unknown node with JFFS2_FEATURE_RWCOMPAT_COPY */
			jffs2_garbage_collect_pristine(c, NULL, raw);
		} else {
			/* Just mark it obsolete */
			jffs2_mark_node_obsolete(c, raw);
		}
		up(&c->alloc_sem);
		goto eraseit_lock;
	}

	ic = jffs2_raw_ref_to_ic(raw);

#ifdef CONFIG_JFFS2_FS_XATTR
	/* When 'ic' refers xattr_datum/xattr_ref, this node is GCed as xattr.
	 * We can decide whether this node is inode or xattr by ic->class.     */
	if (ic->class == RAWNODE_CLASS_XATTR_DATUM
	    || ic->class == RAWNODE_CLASS_XATTR_REF) {
		spin_unlock(&c->erase_completion_lock);

		if (ic->class == RAWNODE_CLASS_XATTR_DATUM) {
			ret = jffs2_garbage_collect_xattr_datum(c, (struct jffs2_xattr_datum *)ic, raw);
		} else {
			ret = jffs2_garbage_collect_xattr_ref(c, (struct jffs2_xattr_ref *)ic, raw);
		}
		goto test_gcnode;
	}
#endif

	/* We need to hold the inocache. Either the erase_completion_lock or
	   the inocache_lock are sufficient; we trade down since the inocache_lock
	   causes less contention. */
	spin_lock(&c->inocache_lock);

	spin_unlock(&c->erase_completion_lock);

	D1(printk(KERN_DEBUG "jffs2_garbage_collect_pass collecting from block @0x%08x. Node @0x%08x(%d), ino #%u\n", jeb->offset, ref_offset(raw), ref_flags(raw), ic->ino));

	/* Three possibilities:
	   1. Inode is already in-core. We must iget it and do proper
	      updating to its fragtree, etc.
	   2. Inode is not in-core, node is REF_PRISTINE. We lock the
	      inocache to prevent a read_inode(), copy the node intact.
	   3. Inode is not in-core, node is not pristine. We must iget()
	      and take the slow path.
	*/

	switch(ic->state) {
	case INO_STATE_CHECKEDABSENT:
		/* It's been checked, but it's not currently in-core.
		   We can just copy any pristine nodes, but have
		   to prevent anyone else from doing read_inode() while
		   we're at it, so we set the state accordingly */
		if (ref_flags(raw) == REF_PRISTINE)
			ic->state = INO_STATE_GC;
		else {
			D1(printk(KERN_DEBUG "Ino #%u is absent but node not REF_PRISTINE. Reading.\n",
				  ic->ino));
		}
		break;

	case INO_STATE_PRESENT:
		/* It's in-core. GC must iget() it. */
		break;

	case INO_STATE_UNCHECKED:
	case INO_STATE_CHECKING:
	case INO_STATE_GC:
		/* Should never happen. We should have finished checking
		   by the time we actually start doing any GC, and since
		   we're holding the alloc_sem, no other garbage collection
		   can happen.
		*/
		printk(KERN_CRIT "Inode #%u already in state %d in jffs2_garbage_collect_pass()!\n",
		       ic->ino, ic->state);
		up(&c->alloc_sem);
		spin_unlock(&c->inocache_lock);
		BUG();

	case INO_STATE_READING:
		/* Someone's currently trying to read it. We must wait for
		   them to finish and then go through the full iget() route
		   to do the GC. However, sometimes read_inode() needs to get
		   the alloc_sem() (for marking nodes invalid) so we must
		   drop the alloc_sem before sleeping. */

		up(&c->alloc_sem);
		D1(printk(KERN_DEBUG "jffs2_garbage_collect_pass() waiting for ino #%u in state %d\n",
			  ic->ino, ic->state));
		sleep_on_spinunlock(&c->inocache_wq, &c->inocache_lock);
		/* And because we dropped the alloc_sem we must start again from the
		   beginning. Ponder chance of livelock here -- we're returning success
		   without actually making any progress.

		   Q: What are the chances that the inode is back in INO_STATE_READING
		   again by the time we next enter this function? And that this happens
		   enough times to cause a real delay?

		   A: Small enough that I don't care :)
		*/
		return 0;
	}

	/* OK. Now if the inode is in state INO_STATE_GC, we are going to copy the
	   node intact, and we don't have to muck about with the fragtree etc.
	   because we know it's not in-core. If it _was_ in-core, we go through
	   all the iget() crap anyway */

	if (ic->state == INO_STATE_GC) {
		spin_unlock(&c->inocache_lock);

		ret = jffs2_garbage_collect_pristine(c, ic, raw);

		spin_lock(&c->inocache_lock);
		ic->state = INO_STATE_CHECKEDABSENT;
		wake_up(&c->inocache_wq);

		if (ret != -EBADFD) {
			spin_unlock(&c->inocache_lock);
			goto test_gcnode;
		}

		/* Fall through if it wanted us to, with inocache_lock held */
	}

	/* Prevent the fairly unlikely race where the gcblock is
	   entirely obsoleted by the final close of a file which had
	   the only valid nodes in the block, followed by erasure,
	   followed by freeing of the ic because the erased block(s)
	   held _all_ the nodes of that inode.... never been seen but
	   it's vaguely possible. */

	inum = ic->ino;
	nlink = ic->nlink;
	spin_unlock(&c->inocache_lock);

	f = jffs2_gc_fetch_inode(c, inum, nlink);
	if (IS_ERR(f)) {
		ret = PTR_ERR(f);
		goto release_sem;
	}
	if (!f) {
		ret = 0;
		goto release_sem;
	}

	ret = jffs2_garbage_collect_live(c, jeb, raw, f);

	jffs2_gc_release_inode(c, f);

 test_gcnode:
	if (jeb->dirty_size == gcblock_dirty && !ref_obsolete(jeb->gc_node)) {
		/* Eep. This really should never happen. GC is broken */
		printk(KERN_ERR "Error garbage collecting node at %08x!\n", ref_offset(jeb->gc_node));
		ret = -ENOSPC;
	}
 release_sem:
	up(&c->alloc_sem);

 eraseit_lock:
	/* If we've finished this block, start it erasing */
	spin_lock(&c->erase_completion_lock);

 eraseit:
	if (c->gcblock && !c->gcblock->used_size) {
		D1(printk(KERN_DEBUG "Block at 0x%08x completely obsoleted by GC. Moving to erase_pending_list\n", c->gcblock->offset));
		/* We're GC'ing an empty block? */
		list_add_tail(&c->gcblock->list, &c->erase_pending_list);
		c->gcblock = NULL;
		c->nr_erasing_blocks++;
		jffs2_erase_pending_trigger(c);
	}
	spin_unlock(&c->erase_completion_lock);