path: root/fs/jffs2/xattr.c

/* -------------------------------------------------------------------------
 *  File: fs/jffs2/xattr.c
 *  XATTR support on JFFS2 FileSystem
 *
 *  Implemented by KaiGai Kohei <kaigai@ak.jp.nec.com>
 *  Copyright (C) 2006 NEC Corporation
 *
 *  For licensing information, see the file 'LICENCE' in the jffs2 directory.
 * ------------------------------------------------------------------------- */

#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/time.h>
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/crc32.h>
#include <linux/jffs2.h>
#include <linux/xattr.h>
#include <linux/mtd/mtd.h>
#include "nodelist.h"
/* -------- xdatum related functions ----------------
 * xattr_datum_hashkey(xprefix, xname, xvalue, xsize)
 *   is used to calcurate xdatum hashkey. The reminder of hashkey into XATTRINDEX_HASHSIZE is
 *   the index of the xattr name/value pair cache (c->xattrindex).
 * unload_xattr_datum(c, xd)
 *   is used to release xattr name/value pair and detach from c->xattrindex.
 * reclaim_xattr_datum(c)
 *   is used to reclaim xattr name/value pairs on the xattr name/value pair cache when
 *   memory usage by cache is over c->xdatum_mem_threshold. Currentry, this threshold 
 *   is hard coded as 32KiB.
 * delete_xattr_datum_node(c, xd)
 *   is used to delete a jffs2 node is dominated by xdatum. When EBS(Erase Block Summary) is
 *   enabled, it overwrites the obsolete node by myself.
 * delete_xattr_datum(c, xd)
 *   is used to delete jffs2_xattr_datum object. It must be called with 0-value of reference
 *   counter. (It means how many jffs2_xattr_ref object refers this xdatum.)
 * do_verify_xattr_datum(c, xd)
 *   is used to load the xdatum informations without name/value pair from the medium.
 *   It's necessary once, because those informations are not collected during mounting
 *   process when EBS is enabled.
 *   0 will be returned, if success. An negative return value means recoverable error, and
 *   positive return value means unrecoverable error. Thus, caller must remove this xdatum
 *   and xref when it returned positive value.
 * do_load_xattr_datum(c, xd)
 *   is used to load name/value pair from the medium.
 *   The meanings of return value is same as do_verify_xattr_datum().
 * load_xattr_datum(c, xd)
 *   is used to be as a wrapper of do_verify_xattr_datum() and do_load_xattr_datum().
 *   If xd need to call do_verify_xattr_datum() at first, it's called before calling
 *   do_load_xattr_datum(). The meanings of return value is same as do_verify_xattr_datum().
 * save_xattr_datum(c, xd, phys_ofs)
 *   is used to write xdatum to medium. xd->version will be incremented.
 * create_xattr_datum(c, xprefix, xname, xvalue, xsize, phys_ofs)
 *   is used to create new xdatum and write to medium.
 * -------------------------------------------------- */

static uint32_t xattr_datum_hashkey(int xprefix, const char *xname, const char *xvalue, int xsize)
{
	int name_len = strlen(xname);

	return crc32(xprefix, xname, name_len) ^ crc32(xprefix, xvalue, xsize);
}

static void unload_xattr_datum(struct jffs2_sb_info *c, struct jffs2_xattr_datum *xd)
{
	/* must be called under down_write(xattr_sem) */
	D1(dbg_xattr("%s: xid=%u, version=%u\n", __FUNCTION__, xd->xid, xd->version));
	if (xd->xname) {
		c->xdatum_mem_usage -= (xd->name_len + 1 + xd->value_len);
		kfree(xd->xname);
	}

	list_del_init(&xd->xindex);
	xd->hashkey = 0;
	xd->xname = NULL;
	xd->xvalue = NULL;
}

static void reclaim_xattr_datum(struct jffs2_sb_info *c)
{
	/* must be called under down_write(xattr_sem) */
	struct jffs2_xattr_datum *xd, *_xd;
	uint32_t target, before;
	static int index = 0;
	int count;

	if (c->xdatum_mem_threshold > c->xdatum_mem_usage)
		return;

	before = c->xdatum_mem_usage;
	target = c->xdatum_mem_usage * 4 / 5; /* 20% reduction */
	for (count = 0; count < XATTRINDEX_HASHSIZE; count++) {
		list_for_each_entry_safe(xd, _xd, &c->xattrindex[index], xindex