mtdswap + ubi results in deadlock

* mtdswap + ubi results in deadlock
@ 2019-10-15 16:59 Emil Lenngren
  2019-10-15 18:59 ` Richard Weinberger
  0 siblings, 1 reply; 4+ messages in thread
From: Emil Lenngren @ 2019-10-15 16:59 UTC (permalink / raw)
  To: linux-mtd

[-- Attachment #1: Type: text/plain, Size: 10984 bytes --]

Hi. I'm trying to use mtdswap together with ubi increase memory.
Normally mtdswap has its own wear leveling but I want ubi to do that
job instead. So I removed all wear leveling and oob usage from mtdswap
(or really it doesn't do wear leveling if the mtd device has no oob)
and am now using it with a gluebi mtd partition on top of ubi. It
works good but in some occasions it deadlocks because ubi internally
uses kmalloc, which in case of low memory, waits for swap to complete.
But swap won't complete until the data is written to flash.

Do you have any idea how to mitigate this issue?

I'm attaching the patched mtdswap.c file. Here is the kernel hung message:

[ 5161.590076] INFO: task kworker/0:0H:4 blocked for more than 61 seconds.
[ 5161.596700]       Tainted: G           O
5.2.0-rc3-00024-g788a024921c4-dirty #175
[ 5161.604615] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
disables this message.
[ 5161.612440] kworker/0:0H    D    0     4      2 0x00000000
[ 5161.617938] Workqueue: kblockd blk_mq_run_work_fn
[ 5161.622663] [<c04afa5d>] (__schedule) from [<c04afc0d>] (schedule+0x29/0x78)
[ 5161.629710] [<c04afc0d>] (schedule) from [<c012b253>] (io_schedule+0xf/0x28)
[ 5161.636771] [<c012b253>] (io_schedule) from [<c023e607>]
(blk_mq_get_tag+0x123/0x1f8)
[ 5161.644604] [<c023e607>] (blk_mq_get_tag) from [<c023b137>]
(blk_mq_get_request+0x8b/0x23c)
[ 5161.652954] [<c023b137>] (blk_mq_get_request) from [<c023c967>]
(blk_mq_make_request+0x87/0x244)
[ 5161.661739] [<c023c967>] (blk_mq_make_request) from [<c0235f81>]
(generic_make_request+0xa5/0x194)
[ 5161.670706] [<c0235f81>] (generic_make_request) from [<c02360a3>]
(submit_bio+0x33/0xf8)
[ 5161.678792] [<c02360a3>] (submit_bio) from [<c0196441>]
(__swap_writepage+0x251/0x280)
[ 5161.686719] [<c0196441>] (__swap_writepage) from [<c01755ed>]
(shrink_page_list+0x6f1/0xacc)
[ 5161.695158] [<c01755ed>] (shrink_page_list) from [<c0175f37>]
(shrink_inactive_list+0x13f/0x26c)
[ 5161.703939] [<c0175f37>] (shrink_inactive_list) from [<c0176649>]
(shrink_node+0x371/0x6a8)
[ 5161.712289] [<c0176649>] (shrink_node) from [<c0176af9>]
(try_to_free_pages+0x179/0x498)
[ 5161.720375] [<c0176af9>] (try_to_free_pages) from [<c0192ecb>]
(__alloc_pages_nodemask+0x30b/0x8c0)
[ 5161.729414] [<c0192ecb>] (__alloc_pages_nodemask) from [<c019bcab>]
(new_slab+0x7f/0x294)
[ 5161.737592] [<c019bcab>] (new_slab) from [<c019cbad>]
(___slab_alloc.constprop.13+0xfd/0x218)
[ 5161.746111] [<c019cbad>] (___slab_alloc.constprop.13) from
[<c019cd47>] (__kmalloc+0x7f/0xc4)
[ 5161.754635] [<c019cd47>] (__kmalloc) from [<c02e0c6b>]
(sync_erase+0x57/0x14c)
[ 5161.761856] [<c02e0c6b>] (sync_erase) from [<c02e1115>]
(__erase_worker+0x21/0x294)
[ 5161.769503] [<c02e1115>] (__erase_worker) from [<c02e1393>]
(erase_worker+0xb/0x44)
[ 5161.777157] [<c02e1393>] (erase_worker) from [<c02e1e03>]
(ubi_wl_flush+0x7f/0xd4)
[ 5161.784725] [<c02e1e03>] (ubi_wl_flush) from [<c02e577f>]
(gluebi_erase+0x113/0x148)
[ 5161.792469] [<c02e577f>] (gluebi_erase) from [<c02d4ccb>]
(mtdswap_erase_block+0x6f/0xc0)
[ 5161.800642] [<c02d4ccb>] (mtdswap_erase_block) from [<c02d4fa5>]
(mtdswap_gc+0x195/0x548)
[ 5161.808810] [<c02d4fa5>] (mtdswap_gc) from [<c02d5691>]
(mtdswap_background+0x19/0x20)
[ 5161.816724] [<c02d5691>] (mtdswap_background) from [<c02d41ff>]
(mtd_queue_rq+0x357/0x40c)
[ 5161.824985] [<c02d41ff>] (mtd_queue_rq) from [<c023cba1>]
(blk_mq_dispatch_rq_list+0x7d/0x378)
[ 5161.833595] [<c023cba1>] (blk_mq_dispatch_rq_list) from
[<c023f273>] (blk_mq_do_dispatch_sched+0x43/0x8c)
[ 5161.843158] [<c023f273>] (blk_mq_do_dispatch_sched) from
[<c023f671>] (blk_mq_sched_dispatch_requests+0x8d/0xf0)
[ 5161.853325] [<c023f671>] (blk_mq_sched_dispatch_requests) from
[<c023badb>] (__blk_mq_run_hw_queue+0x37/0xb4)
[ 5161.863237] [<c023badb>] (__blk_mq_run_hw_queue) from [<c0122909>]
(process_one_work+0x11d/0x2a8)
[ 5161.872107] [<c0122909>] (process_one_work) from [<c0122b81>]
(worker_thread+0xed/0x3a0)
[ 5161.880195] [<c0122b81>] (worker_thread) from [<c01263f1>]
(kthread+0xe9/0xf0)
[ 5161.887410] [<c01263f1>] (kthread) from [<c01010f9>]
(ret_from_fork+0x11/0x38)
[ 5161.894625] Exception stack(0xc2841fb0 to 0xc2841ff8)
[ 5161.899672] 1fa0:                                     00000000
00000000 00000000 00000000
[ 5161.907843] 1fc0: 00000000 00000000 00000000 00000000 00000000
00000000 00000000 00000000
[ 5161.916013] 1fe0: 00000000 00000000 00000000 00000000 00000013 00000000
[ 5161.922686] INFO: task kswapd0:86 blocked for more than 61 seconds.
[ 5161.928944]       Tainted: G           O
5.2.0-rc3-00024-g788a024921c4-dirty #175
[ 5161.936858] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
disables this message.
[ 5161.944682] kswapd0         D    0    86      2 0x00000000
[ 5161.950180] [<c04afa5d>] (__schedule) from [<c04afc0d>] (schedule+0x29/0x78)
[ 5161.957222] [<c04afc0d>] (schedule) from [<c012b253>] (io_schedule+0xf/0x28)
[ 5161.964275] [<c012b253>] (io_schedule) from [<c023e607>]
(blk_mq_get_tag+0x123/0x1f8)
[ 5161.972107] [<c023e607>] (blk_mq_get_tag) from [<c023b137>]
(blk_mq_get_request+0x8b/0x23c)
[ 5161.980454] [<c023b137>] (blk_mq_get_request) from [<c023c967>]
(blk_mq_make_request+0x87/0x244)
[ 5161.989230] [<c023c967>] (blk_mq_make_request) from [<c0235f81>]
(generic_make_request+0xa5/0x194)
[ 5161.998210] [<c0235f81>] (generic_make_request) from [<c02360a3>]
(submit_bio+0x33/0xf8)
[ 5162.006304] [<c02360a3>] (submit_bio) from [<c0196441>]
(__swap_writepage+0x251/0x280)
[ 5162.014224] [<c0196441>] (__swap_writepage) from [<c01755ed>]
(shrink_page_list+0x6f1/0xacc)
[ 5162.022661] [<c01755ed>] (shrink_page_list) from [<c0175f37>]
(shrink_inactive_list+0x13f/0x26c)
[ 5162.031442] [<c0175f37>] (shrink_inactive_list) from [<c0176649>]
(shrink_node+0x371/0x6a8)
[ 5162.039785] [<c0176649>] (shrink_node) from [<c0177077>] (kswapd+0x25f/0x548)
[ 5162.046922] [<c0177077>] (kswapd) from [<c01263f1>] (kthread+0xe9/0xf0)
[ 5162.053537] [<c01263f1>] (kthread) from [<c01010f9>]
(ret_from_fork+0x11/0x38)
[ 5162.060751] Exception stack(0xc293ffb0 to 0xc293fff8)
[ 5162.065797] ffa0:                                     00000000
00000000 00000000 00000000
[ 5162.073969] ffc0: 00000000 00000000 00000000 00000000 00000000
00000000 00000000 00000000
[ 5162.082140] ffe0: 00000000 00000000 00000000 00000000 00000013 00000000
[ 5162.088878] INFO: task klogd:151 blocked for more than 61 seconds.
[ 5162.095068]       Tainted: G           O
5.2.0-rc3-00024-g788a024921c4-dirty #175
[ 5162.102977] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
disables this message.
[ 5162.110798] klogd           D    0   151      1 0x00000000
[ 5162.116289] [<c04afa5d>] (__schedule) from [<c04afc0d>] (schedule+0x29/0x78)
[ 5162.123342] [<c04afc0d>] (schedule) from [<c012b253>] (io_schedule+0xf/0x28)
[ 5162.130393] [<c012b253>] (io_schedule) from [<c023e607>]
(blk_mq_get_tag+0x123/0x1f8)
[ 5162.138214] [<c023e607>] (blk_mq_get_tag) from [<c023b137>]
(blk_mq_get_request+0x8b/0x23c)
[ 5162.146563] [<c023b137>] (blk_mq_get_request) from [<c023c967>]
(blk_mq_make_request+0x87/0x244)
[ 5162.155352] [<c023c967>] (blk_mq_make_request) from [<c0235f81>]
(generic_make_request+0xa5/0x194)
[ 5162.164309] [<c0235f81>] (generic_make_request) from [<c02360a3>]
(submit_bio+0x33/0xf8)
[ 5162.172397] [<c02360a3>] (submit_bio) from [<c0196441>]
(__swap_writepage+0x251/0x280)
[ 5162.180314] [<c0196441>] (__swap_writepage) from [<c01755ed>]
(shrink_page_list+0x6f1/0xacc)
[ 5162.188743] [<c01755ed>] (shrink_page_list) from [<c0175f37>]
(shrink_inactive_list+0x13f/0x26c)
[ 5162.197524] [<c0175f37>] (shrink_inactive_list) from [<c0176649>]
(shrink_node+0x371/0x6a8)
[ 5162.205873] [<c0176649>] (shrink_node) from [<c0176af9>]
(try_to_free_pages+0x179/0x498)
[ 5162.213961] [<c0176af9>] (try_to_free_pages) from [<c0192ecb>]
(__alloc_pages_nodemask+0x30b/0x8c0)
[ 5162.223004] [<c0192ecb>] (__alloc_pages_nodemask) from [<c019bcab>]
(new_slab+0x7f/0x294)
[ 5162.231185] [<c019bcab>] (new_slab) from [<c019cbad>]
(___slab_alloc.constprop.13+0xfd/0x218)
[ 5162.239700] [<c019cbad>] (___slab_alloc.constprop.13) from
[<c019dfeb>] (__kmalloc_track_caller+0x7f/0xc4)
[ 5162.249355] [<c019dfeb>] (__kmalloc_track_caller) from [<c0391c0b>]
(__kmalloc_reserve.constprop.23+0x17/0x44)
[ 5162.259353] [<c0391c0b>] (__kmalloc_reserve.constprop.23) from
[<c0391c9b>] (__alloc_skb+0x63/0x118)
[ 5162.268482] [<c0391c9b>] (__alloc_skb) from [<c0392433>]
(alloc_skb_with_frags+0x27/0x104)
[ 5162.276745] [<c0392433>] (alloc_skb_with_frags) from [<c038d4ed>]
(sock_alloc_send_pskb+0x1ad/0x1c4)
[ 5162.285878] [<c038d4ed>] (sock_alloc_send_pskb) from [<c0402141>]
(unix_dgram_sendmsg+0x12d/0x3a4)
[ 5162.294836] [<c0402141>] (unix_dgram_sendmsg) from [<c038ab2f>]
(sock_sendmsg+0xb/0x18)
[ 5162.302840] [<c038ab2f>] (sock_sendmsg) from [<c038b917>]
(__sys_sendto+0x77/0x9c)
[ 5162.310409] [<c038b917>] (__sys_sendto) from [<c038b94f>] (sys_send+0xf/0x14)
[ 5162.317537] [<c038b94f>] (sys_send) from [<c0101001>]
(ret_fast_syscall+0x1/0x62)
[ 5162.325012] Exception stack(0xc215ffa8 to 0xc215fff0)
[ 5162.330064] ffa0:                   00000001 0009f008 00000003
0009f180 0000002d 00004000
[ 5162.338231] ffc0: 00000001 0009f008 00000014 00000121 ffffffff
b6fa9000 000819b2 be910cd0
[ 5162.346401] ffe0: 00000000 be910c0c b6f50dcb b6f544d8
[ 5162.351577] INFO: task ntpd:267 blocked for more than 62 seconds.
[ 5162.357672]       Tainted: G           O
5.2.0-rc3-00024-g788a024921c4-dirty #175
[ 5162.365590] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
disables this message.
[ 5162.373413] ntpd            D    0   267      1 0x00000001
[ 5162.378904] [<c04afa5d>] (__schedule) from [<c04afc0d>] (schedule+0x29/0x78)
[ 5162.385957] [<c04afc0d>] (schedule) from [<c012b253>] (io_schedule+0xf/0x28)
[ 5162.393011] [<c012b253>] (io_schedule) from [<c023e607>]
(blk_mq_get_tag+0x123/0x1f8)
[ 5162.400841] [<c023e607>] (blk_mq_get_tag) from [<c023b137>]
(blk_mq_get_request+0x8b/0x23c)
[ 5162.409183] [<c023b137>] (blk_mq_get_request) from [<c023c967>]
(blk_mq_make_request+0x87/0x244)
[ 5162.417968] [<c023c967>] (blk_mq_make_request) from [<c0235f81>]
(generic_make_request+0xa5/0x194)
[ 5162.426925] [<c0235f81>] (generic_make_request) from [<c02360a3>]
(submit_bio+0x33/0xf8)
[ 5162.435013] [<c02360a3>] (submit_bio) from [<c01965cf>]
(swap_readpage+0x133/0x198)
[ 5162.442669] [<c01965cf>] (swap_readpage) from [<c0196fcd>]
(read_swap_cache_async+0x2d/0x40)
[ 5162.451102] [<c0196fcd>] (read_swap_cache_async) from [<c0197321>]
(swapin_readahead+0x81/0x32c)
[ 5162.459887] [<c0197321>] (swapin_readahead) from [<c0185f57>]
(do_swap_page+0x2bf/0x3ac)
[ 5162.467971] [<c0185f57>] (do_swap_page) from [<c018651f>]
(handle_mm_fault+0x293/0x750)
[ 5162.475977] [<c018651f>] (handle_mm_fault) from [<c010d633>]
(do_page_fault+0xd3/0x280)
[ 5162.483982] [<c010d633>] (do_page_fault) from [<c010d8f1>]
(do_DataAbort+0x2d/0x78)
[ 5162.491636] [<c010d8f1>] (do_DataAbort) from [<c0101e4f>]
(__dabt_usr+0x4f/0x60)

/Emil

[-- Attachment #2: mtdswap.c --]
[-- Type: text/x-csrc, Size: 35567 bytes --]

/*
 * Swap block device support for MTDs
 * Turns an MTD device into a swap device with block wear leveling
 *
 * Copyright © 2007,2011 Nokia Corporation. All rights reserved.
 *
 * Authors: Jarkko Lavinen <jarkko.lavinen@nokia.com>
 *
 * Based on Richard Purdie's earlier implementation in 2007. Background
 * support and lock-less operation written by Adrian Hunter.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * version 2 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 for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/blktrans.h>
#include <linux/rbtree.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/genhd.h>
#include <linux/swap.h>
#include <linux/debugfs.h>
#include <linux/seq_file.h>
#include <linux/device.h>
#include <linux/math64.h>

#define MTDSWAP_PREFIX "mtdswap"

/*
 * The number of free eraseblocks when GC should stop
 */
#define CLEAN_BLOCK_THRESHOLD	20

/*
 * Number of free eraseblocks below which GC can also collect low frag
 * blocks.
 */
#define LOW_FRAG_GC_THRESHOLD	5

/*
 * Wear level cost amortization. We want to do wear leveling on the background
 * without disturbing gc too much. This is made by defining max GC frequency.
 * Frequency value 6 means 1/6 of the GC passes will pick an erase block based
 * on the biggest wear difference rather than the biggest dirtiness.
 *
 * The lower freq2 should be chosen so that it makes sure the maximum erase
 * difference will decrease even if a malicious application is deliberately
 * trying to make erase differences large.
 */
#define MAX_ERASE_DIFF		4000
#define COLLECT_NONDIRTY_BASE	MAX_ERASE_DIFF
#define COLLECT_NONDIRTY_FREQ1	6
#define COLLECT_NONDIRTY_FREQ2	4

#define PAGE_UNDEF		UINT_MAX
#define BLOCK_UNDEF		UINT_MAX
#define BLOCK_ERROR		(UINT_MAX - 1)
#define BLOCK_MAX		(UINT_MAX - 2)

#define EBLOCK_BAD		(1 << 0)
#define EBLOCK_NOMAGIC		(1 << 1)
#define EBLOCK_BITFLIP		(1 << 2)
#define EBLOCK_FAILED		(1 << 3)
#define EBLOCK_READERR		(1 << 4)
#define EBLOCK_IDX_SHIFT	5

struct swap_eb {
	struct rb_node rb;
	struct rb_root *root;

	unsigned int flags;
	unsigned int active_count;
	unsigned int erase_count;
	unsigned int pad;		/* speeds up pointer decrement */
};

#define MTDSWAP_ECNT_MIN(rbroot) (rb_entry(rb_first(rbroot), struct swap_eb, \
				rb)->erase_count)
#define MTDSWAP_ECNT_MAX(rbroot) (rb_entry(rb_last(rbroot), struct swap_eb, \
				rb)->erase_count)

struct mtdswap_tree {
	struct rb_root root;
	unsigned int count;
};

enum {
	MTDSWAP_CLEAN,
	MTDSWAP_USED,
	MTDSWAP_LOWFRAG,
	MTDSWAP_HIFRAG,
	MTDSWAP_DIRTY,
	MTDSWAP_BITFLIP,
	MTDSWAP_FAILING,
	MTDSWAP_TREE_CNT,
};

struct mtdswap_dev {
	struct mtd_blktrans_dev *mbd_dev;
	struct mtd_info *mtd;
	struct device *dev;

	unsigned int *page_data;
	unsigned int *revmap;

	unsigned int eblks;
	unsigned int spare_eblks;
	unsigned int pages_per_eblk;
	unsigned int max_erase_count;
	struct swap_eb *eb_data;

	struct mtdswap_tree trees[MTDSWAP_TREE_CNT];

	unsigned long long sect_read_count;
	unsigned long long sect_write_count;
	unsigned long long mtd_write_count;
	unsigned long long mtd_read_count;
	unsigned long long discard_count;
	unsigned long long discard_page_count;

	unsigned int curr_write_pos;
	struct swap_eb *curr_write;

	char *page_buf;
	char *oob_buf;
};

struct mtdswap_oobdata {
	__le16 magic;
	__le32 count;
} __packed;

#define MTDSWAP_MAGIC_CLEAN	0x2095
#define MTDSWAP_MAGIC_DIRTY	(MTDSWAP_MAGIC_CLEAN + 1)
#define MTDSWAP_TYPE_CLEAN	0
#define MTDSWAP_TYPE_DIRTY	1
#define MTDSWAP_OOBSIZE		sizeof(struct mtdswap_oobdata)

#define MTDSWAP_ERASE_RETRIES	3 /* Before marking erase block bad */
#define MTDSWAP_IO_RETRIES	3

enum {
	MTDSWAP_SCANNED_CLEAN,
	MTDSWAP_SCANNED_DIRTY,
	MTDSWAP_SCANNED_BITFLIP,
	MTDSWAP_SCANNED_BAD,
};

/*
 * In the worst case mtdswap_writesect() has allocated the last clean
 * page from the current block and is then pre-empted by the GC
 * thread. The thread can consume a full erase block when moving a
 * block.
 */
#define MIN_SPARE_EBLOCKS	2
#define MIN_ERASE_BLOCKS	(MIN_SPARE_EBLOCKS + 1)

#define TREE_ROOT(d, name) (&d->trees[MTDSWAP_ ## name].root)
#define TREE_EMPTY(d, name) (TREE_ROOT(d, name)->rb_node == NULL)
#define TREE_NONEMPTY(d, name) (!TREE_EMPTY(d, name))
#define TREE_COUNT(d, name) (d->trees[MTDSWAP_ ## name].count)

#define MTDSWAP_MBD_TO_MTDSWAP(dev) ((struct mtdswap_dev *)dev->priv)

static char partitions[128] = "";
module_param_string(partitions, partitions, sizeof(partitions), 0444);
MODULE_PARM_DESC(partitions, "MTD partition numbers to use as swap "
		"partitions=\"1,3,5\"");

static unsigned int spare_eblocks = 10;
module_param(spare_eblocks, uint, 0444);
MODULE_PARM_DESC(spare_eblocks, "Percentage of spare erase blocks for "
		"garbage collection (default 10%)");

static bool header; /* false */
module_param(header, bool, 0444);
MODULE_PARM_DESC(header,
		"Include builtin swap header (default 0, without header)");

static int mtdswap_gc(struct mtdswap_dev *d, unsigned int background);

static int mtdswap_can_use_oob(struct mtd_info *mtd)
{
	return mtd->oobsize && mtd->oobavail >= MTDSWAP_OOBSIZE;
}

static loff_t mtdswap_eb_offset(struct mtdswap_dev *d, struct swap_eb *eb)
{
	return (loff_t)(eb - d->eb_data) * d->mtd->erasesize;
}

static void mtdswap_eb_detach(struct mtdswap_dev *d, struct swap_eb *eb)
{
	unsigned int oldidx;
	struct mtdswap_tree *tp;

	if (eb->root) {
		tp = container_of(eb->root, struct mtdswap_tree, root);
		oldidx = tp - &d->trees[0];

		d->trees[oldidx].count--;
		rb_erase(&eb->rb, eb->root);
	}
}

static void __mtdswap_rb_add(struct rb_root *root, struct swap_eb *eb)
{
	struct rb_node **p, *parent = NULL;
	struct swap_eb *cur;

	p = &root->rb_node;
	while (*p) {
		parent = *p;
		cur = rb_entry(parent, struct swap_eb, rb);
		if (eb->erase_count > cur->erase_count)
			p = &(*p)->rb_right;
		else
			p = &(*p)->rb_left;
	}

	rb_link_node(&eb->rb, parent, p);
	rb_insert_color(&eb->rb, root);
}

static void mtdswap_rb_add(struct mtdswap_dev *d, struct swap_eb *eb, int idx)
{
	struct rb_root *root;

	if (eb->root == &d->trees[idx].root)
		return;

	mtdswap_eb_detach(d, eb);
	root = &d->trees[idx].root;
	__mtdswap_rb_add(root, eb);
	eb->root = root;
	d->trees[idx].count++;
}

static struct rb_node *mtdswap_rb_index(struct rb_root *root, unsigned int idx)
{
	struct rb_node *p;
	unsigned int i;

	p = rb_first(root);
	i = 0;
	while (i < idx && p) {
		p = rb_next(p);
		i++;
	}

	return p;
}

static int mtdswap_handle_badblock(struct mtdswap_dev *d, struct swap_eb *eb)
{
	int ret;
	loff_t offset;

	d->spare_eblks--;
	eb->flags |= EBLOCK_BAD;
	mtdswap_eb_detach(d, eb);
	eb->root = NULL;

	/* badblocks not supported */
	if (!mtd_can_have_bb(d->mtd))
		return 1;

	offset = mtdswap_eb_offset(d, eb);
	dev_warn(d->dev, "Marking bad block at %08llx\n", offset);
	ret = mtd_block_markbad(d->mtd, offset);

	if (ret) {
		dev_warn(d->dev, "Mark block bad failed for block at %08llx "
			"error %d\n", offset, ret);
		return ret;
	}

	return 1;

}

static int mtdswap_handle_write_error(struct mtdswap_dev *d, struct swap_eb *eb)
{
	unsigned int marked = eb->flags & EBLOCK_FAILED;
	struct swap_eb *curr_write = d->curr_write;

	eb->flags |= EBLOCK_FAILED;
	if (curr_write == eb) {
		d->curr_write = NULL;

		if (!marked && d->curr_write_pos != 0) {
			mtdswap_rb_add(d, eb, MTDSWAP_FAILING);
			return 0;
		}
	}

	return mtdswap_handle_badblock(d, eb);
}

static int mtdswap_read_oob(struct mtdswap_dev *d, loff_t from,
			struct mtd_oob_ops *ops)
{
	int ret = mtd_read_oob(d->mtd, from, ops);

	if (mtd_is_bitflip(ret))
		return ret;

	if (ret) {
		dev_warn(d->dev, "Read OOB failed %d for block at %08llx\n",
			ret, from);
		return ret;
	}

	if (ops->oobretlen < ops->ooblen) {
		dev_warn(d->dev, "Read OOB return short read (%zd bytes not "
			"%zd) for block at %08llx\n",
			ops->oobretlen, ops->ooblen, from);
		return -EIO;
	}

	return 0;
}

static int mtdswap_read_markers(struct mtdswap_dev *d, struct swap_eb *eb)
{
	struct mtdswap_oobdata *data, *data2;
	int ret;
	loff_t offset;
	struct mtd_oob_ops ops;

	if (!mtdswap_can_use_oob(d->mtd)) {
		eb->flags |= EBLOCK_NOMAGIC;
		return MTDSWAP_SCANNED_DIRTY;
	}

	offset = mtdswap_eb_offset(d, eb);

	/* Check first if the block is bad. */
	if (mtd_can_have_bb(d->mtd) && mtd_block_isbad(d->mtd, offset))
		return MTDSWAP_SCANNED_BAD;

	ops.ooblen = 2 * d->mtd->oobavail;
	ops.oobbuf = d->oob_buf;
	ops.ooboffs = 0;
	ops.datbuf = NULL;
	ops.mode = MTD_OPS_AUTO_OOB;

	ret = mtdswap_read_oob(d, offset, &ops);

	if (ret && !mtd_is_bitflip(ret))
		return ret;

	data = (struct mtdswap_oobdata *)d->oob_buf;
	data2 = (struct mtdswap_oobdata *)
		(d->oob_buf + d->mtd->oobavail);

	if (le16_to_cpu(data->magic) == MTDSWAP_MAGIC_CLEAN) {
		eb->erase_count = le32_to_cpu(data->count);
		if (mtd_is_bitflip(ret))
			ret = MTDSWAP_SCANNED_BITFLIP;
		else {
			if (le16_to_cpu(data2->magic) == MTDSWAP_MAGIC_DIRTY)
				ret = MTDSWAP_SCANNED_DIRTY;
			else
				ret = MTDSWAP_SCANNED_CLEAN;
		}
	} else {
		eb->flags |= EBLOCK_NOMAGIC;
		ret = MTDSWAP_SCANNED_DIRTY;
	}

	return ret;
}

static int mtdswap_write_marker(struct mtdswap_dev *d, struct swap_eb *eb,
				u16 marker)
{
	struct mtdswap_oobdata n;
	int ret;
	loff_t offset;
	struct mtd_oob_ops ops;

	if (!mtdswap_can_use_oob(d->mtd)) {
		return 0;
	}

	ops.ooboffs = 0;
	ops.oobbuf = (uint8_t *)&n;
	ops.mode = MTD_OPS_AUTO_OOB;
	ops.datbuf = NULL;

	if (marker == MTDSWAP_TYPE_CLEAN) {
		n.magic = cpu_to_le16(MTDSWAP_MAGIC_CLEAN);
		n.count = cpu_to_le32(eb->erase_count);
		ops.ooblen = MTDSWAP_OOBSIZE;
		offset = mtdswap_eb_offset(d, eb);
	} else {
		n.magic = cpu_to_le16(MTDSWAP_MAGIC_DIRTY);
		ops.ooblen = sizeof(n.magic);
		offset = mtdswap_eb_offset(d, eb) + d->mtd->writesize;
	}

	ret = mtd_write_oob(d->mtd, offset, &ops);

	if (ret) {
		dev_warn(d->dev, "Write OOB failed for block at %08llx "
			"error %d\n", offset, ret);
		if (ret == -EIO || mtd_is_eccerr(ret))
			mtdswap_handle_write_error(d, eb);
		return ret;
	}

	if (ops.oobretlen != ops.ooblen) {
		dev_warn(d->dev, "Short OOB write for block at %08llx: "
			"%zd not %zd\n",
			offset, ops.oobretlen, ops.ooblen);
		return ret;
	}

	return 0;
}

/*
 * Are there any erase blocks without MAGIC_CLEAN header, presumably
 * because power was cut off after erase but before header write? We
 * need to guestimate the erase count.
 */
static void mtdswap_check_counts(struct mtdswap_dev *d)
{
	struct rb_root hist_root = RB_ROOT;
	struct rb_node *medrb;
	struct swap_eb *eb;
	unsigned int i, cnt, median;

	cnt = 0;
	for (i = 0; i < d->eblks; i++) {
		eb = d->eb_data + i;

		if (eb->flags & (EBLOCK_NOMAGIC | EBLOCK_BAD | EBLOCK_READERR))
			continue;

		__mtdswap_rb_add(&hist_root, eb);
		cnt++;
	}

	if (cnt == 0)
		return;

	medrb = mtdswap_rb_index(&hist_root, cnt / 2);
	median = rb_entry(medrb, struct swap_eb, rb)->erase_count;

	d->max_erase_count = MTDSWAP_ECNT_MAX(&hist_root);

	for (i = 0; i < d->eblks; i++) {
		eb = d->eb_data + i;

		if (eb->flags & (EBLOCK_NOMAGIC | EBLOCK_READERR))
			eb->erase_count = median;

		if (eb->flags & (EBLOCK_NOMAGIC | EBLOCK_BAD | EBLOCK_READERR))
			continue;

		rb_erase(&eb->rb, &hist_root);
	}
}

static void mtdswap_scan_eblks(struct mtdswap_dev *d)
{
	int status;
	unsigned int i, idx;
	struct swap_eb *eb;

	for (i = 0; i < d->eblks; i++) {
		eb = d->eb_data + i;

		status = mtdswap_read_markers(d, eb);
		if (status < 0)
			eb->flags |= EBLOCK_READERR;
		else if (status == MTDSWAP_SCANNED_BAD) {
			eb->flags |= EBLOCK_BAD;
			continue;
		}

		switch (status) {
		case MTDSWAP_SCANNED_CLEAN:
			idx = MTDSWAP_CLEAN;
			break;
		case MTDSWAP_SCANNED_DIRTY:
		case MTDSWAP_SCANNED_BITFLIP:
			idx = MTDSWAP_DIRTY;
			break;
		default:
			idx = MTDSWAP_FAILING;
		}

		eb->flags |= (idx << EBLOCK_IDX_SHIFT);
	}

	mtdswap_check_counts(d);

	for (i = 0; i < d->eblks; i++) {
		eb = d->eb_data + i;

		if (eb->flags & EBLOCK_BAD)
			continue;

		idx = eb->flags >> EBLOCK_IDX_SHIFT;
		mtdswap_rb_add(d, eb, idx);
	}
}

/*
 * Place eblk into a tree corresponding to its number of active blocks
 * it contains.
 */
static void mtdswap_store_eb(struct mtdswap_dev *d, struct swap_eb *eb)
{
	unsigned int weight = eb->active_count;
	unsigned int maxweight = d->pages_per_eblk;

	if (eb == d->curr_write)
		return;

	if (eb->flags & EBLOCK_BITFLIP)
		mtdswap_rb_add(d, eb, MTDSWAP_BITFLIP);
	else if (eb->flags & (EBLOCK_READERR | EBLOCK_FAILED))
		mtdswap_rb_add(d, eb, MTDSWAP_FAILING);
	if (weight == maxweight)
		mtdswap_rb_add(d, eb, MTDSWAP_USED);
	else if (weight == 0)
		mtdswap_rb_add(d, eb, MTDSWAP_DIRTY);
	else if (weight > (maxweight/2))
		mtdswap_rb_add(d, eb, MTDSWAP_LOWFRAG);
	else
		mtdswap_rb_add(d, eb, MTDSWAP_HIFRAG);
}

static int mtdswap_erase_block(struct mtdswap_dev *d, struct swap_eb *eb)
{
	struct mtd_info *mtd = d->mtd;
	struct erase_info erase;
	unsigned int retries = 0;
	int ret;

	eb->erase_count++;
	if (eb->erase_count > d->max_erase_count)
		d->max_erase_count = eb->erase_count;

retry:
	memset(&erase, 0, sizeof(struct erase_info));
	erase.addr	= mtdswap_eb_offset(d, eb);
	erase.len	= mtd->erasesize;

	ret = mtd_erase(mtd, &erase);
	if (ret) {
		if (retries++ < MTDSWAP_ERASE_RETRIES) {
			dev_warn(d->dev,
				"erase of erase block %#llx on %s failed",
				erase.addr, mtd->name);
			yield();
			goto retry;
		}

		dev_err(d->dev, "Cannot erase erase block %#llx on %s\n",
			erase.addr, mtd->name);

		mtdswap_handle_badblock(d, eb);
		return -EIO;
	}

	return 0;
}

static int mtdswap_map_free_block(struct mtdswap_dev *d, unsigned int page,
				unsigned int *block)
{
	int ret;
	struct swap_eb *old_eb = d->curr_write;
	struct rb_root *clean_root;
	struct swap_eb *eb;

	if (old_eb == NULL || d->curr_write_pos >= d->pages_per_eblk) {
		do {
			if (TREE_EMPTY(d, CLEAN))
				return -ENOSPC;

			clean_root = TREE_ROOT(d, CLEAN);
			eb = rb_entry(rb_first(clean_root), struct swap_eb, rb);
			rb_erase(&eb->rb, clean_root);
			eb->root = NULL;
			TREE_COUNT(d, CLEAN)--;

			ret = mtdswap_write_marker(d, eb, MTDSWAP_TYPE_DIRTY);
		} while (ret == -EIO || mtd_is_eccerr(ret));

		if (ret)
			return ret;

		d->curr_write_pos = 0;
		d->curr_write = eb;
		if (old_eb)
			mtdswap_store_eb(d, old_eb);
	}

	*block = (d->curr_write - d->eb_data) * d->pages_per_eblk +
		d->curr_write_pos;

	d->curr_write->active_count++;
	d->revmap[*block] = page;
	d->curr_write_pos++;

	return 0;
}

static unsigned int mtdswap_free_page_cnt(struct mtdswap_dev *d)
{
	return TREE_COUNT(d, CLEAN) * d->pages_per_eblk +
		d->pages_per_eblk - d->curr_write_pos;
}

static unsigned int mtdswap_enough_free_pages(struct mtdswap_dev *d)
{
	return mtdswap_free_page_cnt(d) > d->pages_per_eblk;
}

static loff_t mtdswap_blockpos_to_mtdpos(struct mtdswap_dev *d, unsigned int bp)
{
	unsigned int eblk = bp / d->pages_per_eblk;
	unsigned int page_offset_in_eblk = bp % d->pages_per_eblk;

	return eblk * d->mtd->erasesize + (page_offset_in_eblk << PAGE_SHIFT);
}

static int mtdswap_write_block(struct mtdswap_dev *d, char *buf,
			unsigned int page, unsigned int *bp, int gc_context)
{
	struct mtd_info *mtd = d->mtd;
	struct swap_eb *eb;
	size_t retlen;
	loff_t writepos;
	int ret;

retry:
	if (!gc_context)
		while (!mtdswap_enough_free_pages(d))
			if (mtdswap_gc(d, 0) > 0)
				return -ENOSPC;

	ret = mtdswap_map_free_block(d, page, bp);
	eb = d->eb_data + (*bp / d->pages_per_eblk);

	if (ret == -EIO || mtd_is_eccerr(ret)) {
		d->curr_write = NULL;
		eb->active_count--;
		d->revmap[*bp] = PAGE_UNDEF;
		goto retry;
	}

	if (ret < 0)
		return ret;

	writepos = mtdswap_blockpos_to_mtdpos(d, *bp);
	ret =  mtd_write(mtd, writepos, PAGE_SIZE, &retlen, buf);
	if (ret == -EIO || mtd_is_eccerr(ret)) {
		d->curr_write_pos--;
		eb->active_count--;
		d->revmap[*bp] = PAGE_UNDEF;
		mtdswap_handle_write_error(d, eb);
		goto retry;
	}

	if (ret < 0) {
		dev_err(d->dev, "Write to MTD device failed: %d (%zd written)",
			ret, retlen);
		goto err;
	}

	if (retlen != PAGE_SIZE) {
		dev_err(d->dev, "Short write to MTD device: %zd written",
			retlen);
		ret = -EIO;
		goto err;
	}

	return ret;

err:
	d->curr_write_pos--;
	eb->active_count--;
	d->revmap[*bp] = PAGE_UNDEF;

	return ret;
}

static int mtdswap_move_block(struct mtdswap_dev *d, unsigned int oldblock,
		unsigned int *newblock)
{
	struct mtd_info *mtd = d->mtd;
	struct swap_eb *eb, *oldeb;
	int ret;
	size_t retlen;
	unsigned int page, retries;
	loff_t readpos;

	page = d->revmap[oldblock];
	readpos = mtdswap_blockpos_to_mtdpos(d, oldblock);
	retries = 0;

retry:
	ret = mtd_read(mtd, readpos, PAGE_SIZE, &retlen, d->page_buf);

	if (ret < 0 && !mtd_is_bitflip(ret)) {
		oldeb = d->eb_data + oldblock / d->pages_per_eblk;
		oldeb->flags |= EBLOCK_READERR;

		dev_err(d->dev, "Read Error: %d (block %u)\n", ret,
			oldblock);
		retries++;
		if (retries < MTDSWAP_IO_RETRIES)
			goto retry;

		goto read_error;
	}

	if (retlen != PAGE_SIZE) {
		dev_err(d->dev, "Short read: %zd (block %u)\n", retlen,
		       oldblock);
		ret = -EIO;
		goto read_error;
	}

	ret = mtdswap_write_block(d, d->page_buf, page, newblock, 1);
	if (ret < 0) {
		d->page_data[page] = BLOCK_ERROR;
		dev_err(d->dev, "Write error: %d\n", ret);
		return ret;
	}

	eb = d->eb_data + *newblock / d->pages_per_eblk;
	d->page_data[page] = *newblock;
	d->revmap[oldblock] = PAGE_UNDEF;
	eb = d->eb_data + oldblock / d->pages_per_eblk;
	eb->active_count--;

	return 0;

read_error:
	d->page_data[page] = BLOCK_ERROR;
	d->revmap[oldblock] = PAGE_UNDEF;
	return ret;
}

static int mtdswap_gc_eblock(struct mtdswap_dev *d, struct swap_eb *eb)
{
	unsigned int i, block, eblk_base, newblock;
	int ret, errcode;

	errcode = 0;
	eblk_base = (eb - d->eb_data) * d->pages_per_eblk;

	for (i = 0; i < d->pages_per_eblk; i++) {
		if (d->spare_eblks < MIN_SPARE_EBLOCKS)
			return -ENOSPC;

		block = eblk_base + i;
		if (d->revmap[block] == PAGE_UNDEF)
			continue;

		ret = mtdswap_move_block(d, block, &newblock);
		if (ret < 0 && !errcode)
			errcode = ret;
	}

	return errcode;
}

static int __mtdswap_choose_gc_tree(struct mtdswap_dev *d)
{
	int idx, stopat;

	if (TREE_COUNT(d, CLEAN) < LOW_FRAG_GC_THRESHOLD)
		stopat = MTDSWAP_LOWFRAG;
	else
		stopat = MTDSWAP_HIFRAG;

	for (idx = MTDSWAP_BITFLIP; idx >= stopat; idx--)
		if (d->trees[idx].root.rb_node != NULL)
			return idx;

	return -1;
}

static int mtdswap_wlfreq(unsigned int maxdiff)
{
	unsigned int h, x, y, dist, base;

	/*
	 * Calculate linear ramp down from f1 to f2 when maxdiff goes from
	 * MAX_ERASE_DIFF to MAX_ERASE_DIFF + COLLECT_NONDIRTY_BASE.  Similar
	 * to triangle with height f1 - f1 and width COLLECT_NONDIRTY_BASE.
	 */

	dist = maxdiff - MAX_ERASE_DIFF;
	if (dist > COLLECT_NONDIRTY_BASE)
		dist = COLLECT_NONDIRTY_BASE;

	/*
	 * Modelling the slop as right angular triangle with base
	 * COLLECT_NONDIRTY_BASE and height freq1 - freq2. The ratio y/x is
	 * equal to the ratio h/base.
	 */
	h = COLLECT_NONDIRTY_FREQ1 - COLLECT_NONDIRTY_FREQ2;
	base = COLLECT_NONDIRTY_BASE;

	x = dist - base;
	y = (x * h + base / 2) / base;

	return COLLECT_NONDIRTY_FREQ2 + y;
}

static int mtdswap_choose_wl_tree(struct mtdswap_dev *d)
{
	static unsigned int pick_cnt;
	unsigned int i, idx = -1, wear, max;
	struct rb_root *root;

	max = 0;
	for (i = 0; i <= MTDSWAP_DIRTY; i++) {
		root = &d->trees[i].root;
		if (root->rb_node == NULL)
			continue;

		wear = d->max_erase_count - MTDSWAP_ECNT_MIN(root);
		if (wear > max) {
			max = wear;
			idx = i;
		}
	}

	if (max > MAX_ERASE_DIFF && pick_cnt >= mtdswap_wlfreq(max) - 1) {
		pick_cnt = 0;
		return idx;
	}

	pick_cnt++;
	return -1;
}

static int mtdswap_choose_gc_tree(struct mtdswap_dev *d,
				unsigned int background)
{
	int idx;

	if (TREE_NONEMPTY(d, FAILING) &&
		(background || (TREE_EMPTY(d, CLEAN) && TREE_EMPTY(d, DIRTY))))
		return MTDSWAP_FAILING;

	idx = mtdswap_choose_wl_tree(d);
	if (idx >= MTDSWAP_CLEAN)
		return idx;

	return __mtdswap_choose_gc_tree(d);
}

static struct swap_eb *mtdswap_pick_gc_eblk(struct mtdswap_dev *d,
					unsigned int background)
{
	struct rb_root *rp = NULL;
	struct swap_eb *eb = NULL;
	int idx;

	if (background && TREE_COUNT(d, CLEAN) > CLEAN_BLOCK_THRESHOLD &&
		TREE_EMPTY(d, DIRTY) && TREE_EMPTY(d, FAILING))
		return NULL;

	idx = mtdswap_choose_gc_tree(d, background);
	if (idx < 0)
		return NULL;

	rp = &d->trees[idx].root;
	eb = rb_entry(rb_first(rp), struct swap_eb, rb);

	rb_erase(&eb->rb, rp);
	eb->root = NULL;
	d->trees[idx].count--;
	return eb;
}

static unsigned int mtdswap_test_patt(unsigned int i)
{
	return i % 2 ? 0x55555555 : 0xAAAAAAAA;
}

static unsigned int mtdswap_eblk_passes(struct mtdswap_dev *d,
					struct swap_eb *eb)
{
	struct mtd_info *mtd = d->mtd;
	unsigned int test, i, j, patt, mtd_pages;
	loff_t base, pos;
	unsigned int *p1 = (unsigned int *)d->page_buf;
	unsigned char *p2 = (unsigned char *)d->oob_buf;
	struct mtd_oob_ops ops;
	int ret;

	ops.mode = MTD_OPS_AUTO_OOB;
	ops.len = mtd->writesize;
	ops.ooblen = mtd->oobavail;
	ops.ooboffs = 0;
	ops.datbuf = d->page_buf;
	ops.oobbuf = d->oob_buf;
	base = mtdswap_eb_offset(d, eb);
	mtd_pages = d->pages_per_eblk * PAGE_SIZE / mtd->writesize;

	for (test = 0; test < 2; test++) {
		pos = base;
		for (i = 0; i < mtd_pages; i++) {
			patt = mtdswap_test_patt(test + i);
			memset(d->page_buf, patt, mtd->writesize);
			memset(d->oob_buf, patt, mtd->oobavail);
			ret = mtd_write_oob(mtd, pos, &ops);
			if (ret)
				goto error;

			pos += mtd->writesize;
		}

		pos = base;
		for (i = 0; i < mtd_pages; i++) {
			ret = mtd_read_oob(mtd, pos, &ops);
			if (ret)
				goto error;

			patt = mtdswap_test_patt(test + i);
			for (j = 0; j < mtd->writesize/sizeof(int); j++)
				if (p1[j] != patt)
					goto error;

			for (j = 0; j < mtd->oobavail; j++)
				if (p2[j] != (unsigned char)patt)
					goto error;

			pos += mtd->writesize;
		}

		ret = mtdswap_erase_block(d, eb);
		if (ret)
			goto error;
	}

	eb->flags &= ~EBLOCK_READERR;
	return 1;

error:
	mtdswap_handle_badblock(d, eb);
	return 0;
}

static int mtdswap_gc(struct mtdswap_dev *d, unsigned int background)
{
	struct swap_eb *eb;
	int ret;

	if (d->spare_eblks < MIN_SPARE_EBLOCKS)
		return 1;

	eb = mtdswap_pick_gc_eblk(d, background);
	if (!eb)
		return 1;

	ret = mtdswap_gc_eblock(d, eb);
	if (ret == -ENOSPC)
		return 1;

	if (eb->flags & EBLOCK_FAILED) {
		mtdswap_handle_badblock(d, eb);
		return 0;
	}

	eb->flags &= ~EBLOCK_BITFLIP;
	ret = mtdswap_erase_block(d, eb);
	if ((eb->flags & EBLOCK_READERR) &&
		(ret || !mtdswap_can_use_oob(d->mtd) || !mtdswap_eblk_passes(d, eb)))
		return 0;

	if (ret == 0)
		ret = mtdswap_write_marker(d, eb, MTDSWAP_TYPE_CLEAN);

	if (ret == 0)
		mtdswap_rb_add(d, eb, MTDSWAP_CLEAN);
	else if (ret != -EIO && !mtd_is_eccerr(ret))
		mtdswap_rb_add(d, eb, MTDSWAP_DIRTY);

	return 0;
}

static void mtdswap_background(struct mtd_blktrans_dev *dev)
{
	struct mtdswap_dev *d = MTDSWAP_MBD_TO_MTDSWAP(dev);
	int ret;

	while (1) {
		ret = mtdswap_gc(d, 1);
		if (ret || mtd_blktrans_cease_background(dev))
			return;
	}
}

static void mtdswap_cleanup(struct mtdswap_dev *d)
{
	vfree(d->eb_data);
	vfree(d->revmap);
	vfree(d->page_data);
	kfree(d->oob_buf);
	kfree(d->page_buf);
}

static int mtdswap_flush(struct mtd_blktrans_dev *dev)
{
	struct mtdswap_dev *d = MTDSWAP_MBD_TO_MTDSWAP(dev);

	mtd_sync(d->mtd);
	return 0;
}

static unsigned int mtdswap_badblocks(struct mtd_info *mtd, uint64_t size)
{
	loff_t offset;
	unsigned int badcnt;

	badcnt = 0;

	if (mtd_can_have_bb(mtd))
		for (offset = 0; offset < size; offset += mtd->erasesize)
			if (mtd_block_isbad(mtd, offset))
				badcnt++;

	return badcnt;
}

static int mtdswap_writesect(struct mtd_blktrans_dev *dev,
			unsigned long page, char *buf)
{
	struct mtdswap_dev *d = MTDSWAP_MBD_TO_MTDSWAP(dev);
	unsigned int newblock, mapped;
	struct swap_eb *eb;
	int ret;

	d->sect_write_count++;

	if (d->spare_eblks < MIN_SPARE_EBLOCKS)
		return -ENOSPC;

	if (header) {
		/* Ignore writes to the header page */
		if (unlikely(page == 0))
			return 0;

		page--;
	}

	mapped = d->page_data[page];
	if (mapped <= BLOCK_MAX) {
		eb = d->eb_data + (mapped / d->pages_per_eblk);
		eb->active_count--;
		mtdswap_store_eb(d, eb);
		d->page_data[page] = BLOCK_UNDEF;
		d->revmap[mapped] = PAGE_UNDEF;
	}

	ret = mtdswap_write_block(d, buf, page, &newblock, 0);
	d->mtd_write_count++;

	if (ret < 0)
		return ret;

	eb = d->eb_data + (newblock / d->pages_per_eblk);
	d->page_data[page] = newblock;

	return 0;
}

/* Provide a dummy swap header for the kernel */
static int mtdswap_auto_header(struct mtdswap_dev *d, char *buf)
{
	union swap_header *hd = (union swap_header *)(buf);

	memset(buf, 0, PAGE_SIZE - 10);

	hd->info.version = 1;
	hd->info.last_page = d->mbd_dev->size - 1;
	hd->info.nr_badpages = 0;

	memcpy(buf + PAGE_SIZE - 10, "SWAPSPACE2", 10);

	return 0;
}

static int mtdswap_readsect(struct mtd_blktrans_dev *dev,
			unsigned long page, char *buf)
{
	struct mtdswap_dev *d = MTDSWAP_MBD_TO_MTDSWAP(dev);
	struct mtd_info *mtd = d->mtd;
	unsigned int realblock, retries;
	loff_t readpos;
	struct swap_eb *eb;
	size_t retlen;
	int ret;

	d->sect_read_count++;

	if (header) {
		if (unlikely(page == 0))
			return mtdswap_auto_header(d, buf);

		page--;
	}

	realblock = d->page_data[page];
	if (realblock > BLOCK_MAX) {
		memset(buf, 0x0, PAGE_SIZE);
		if (realblock == BLOCK_UNDEF)
			return 0;
		else
			return -EIO;
	}

	eb = d->eb_data + (realblock / d->pages_per_eblk);
	BUG_ON(d->revmap[realblock] == PAGE_UNDEF);

	readpos = mtdswap_blockpos_to_mtdpos(d, realblock);
	retries = 0;

retry:
	ret = mtd_read(mtd, readpos, PAGE_SIZE, &retlen, buf);

	d->mtd_read_count++;
	if (mtd_is_bitflip(ret)) {
		eb->flags |= EBLOCK_BITFLIP;
		mtdswap_rb_add(d, eb, MTDSWAP_BITFLIP);
		ret = 0;
	}

	if (ret < 0) {
		dev_err(d->dev, "Read error %d\n", ret);
		eb->flags |= EBLOCK_READERR;
		mtdswap_rb_add(d, eb, MTDSWAP_FAILING);
		retries++;
		if (retries < MTDSWAP_IO_RETRIES)
			goto retry;

		return ret;
	}

	if (retlen != PAGE_SIZE) {
		dev_err(d->dev, "Short read %zd\n", retlen);
		return -EIO;
	}

	return 0;
}

static int mtdswap_discard(struct mtd_blktrans_dev *dev, unsigned long first,
			unsigned nr_pages)
{
	struct mtdswap_dev *d = MTDSWAP_MBD_TO_MTDSWAP(dev);
	unsigned long page;
	struct swap_eb *eb;
	unsigned int mapped;

	d->discard_count++;

	for (page = first; page < first + nr_pages; page++) {
		mapped = d->page_data[page];
		if (mapped <= BLOCK_MAX) {
			eb = d->eb_data + (mapped / d->pages_per_eblk);
			eb->active_count--;
			mtdswap_store_eb(d, eb);
			d->page_data[page] = BLOCK_UNDEF;
			d->revmap[mapped] = PAGE_UNDEF;
			d->discard_page_count++;
		} else if (mapped == BLOCK_ERROR) {
			d->page_data[page] = BLOCK_UNDEF;
			d->discard_page_count++;
		}
	}

	return 0;
}

static int mtdswap_show(struct seq_file *s, void *data)
{
	struct mtdswap_dev *d = (struct mtdswap_dev *) s->private;
	unsigned long sum;
	unsigned int count[MTDSWAP_TREE_CNT];
	unsigned int min[MTDSWAP_TREE_CNT];
	unsigned int max[MTDSWAP_TREE_CNT];
	unsigned int i, cw = 0, cwp = 0, cwecount = 0, bb_cnt, mapped, pages;
	uint64_t use_size;
	static const char * const name[] = {
		"clean", "used", "low", "high", "dirty", "bitflip", "failing"
	};

	mutex_lock(&d->mbd_dev->lock);

	for (i = 0; i < MTDSWAP_TREE_CNT; i++) {
		struct rb_root *root = &d->trees[i].root;

		if (root->rb_node) {
			count[i] = d->trees[i].count;
			min[i] = MTDSWAP_ECNT_MIN(root);
			max[i] = MTDSWAP_ECNT_MAX(root);
		} else
			count[i] = 0;
	}

	if (d->curr_write) {
		cw = 1;
		cwp = d->curr_write_pos;
		cwecount = d->curr_write->erase_count;
	}

	sum = 0;
	for (i = 0; i < d->eblks; i++)
		sum += d->eb_data[i].erase_count;

	use_size = (uint64_t)d->eblks * d->mtd->erasesize;
	bb_cnt = mtdswap_badblocks(d->mtd, use_size);

	mapped = 0;
	pages = d->mbd_dev->size;
	for (i = 0; i < pages; i++)
		if (d->page_data[i] != BLOCK_UNDEF)
			mapped++;

	mutex_unlock(&d->mbd_dev->lock);

	for (i = 0; i < MTDSWAP_TREE_CNT; i++) {
		if (!count[i])
			continue;

		if (min[i] != max[i])
			seq_printf(s, "%s:\t%5d erase blocks, erased min %d, "
				"max %d times\n",
				name[i], count[i], min[i], max[i]);
		else
			seq_printf(s, "%s:\t%5d erase blocks, all erased %d "
				"times\n", name[i], count[i], min[i]);
	}

	if (bb_cnt)
		seq_printf(s, "bad:\t%5u erase blocks\n", bb_cnt);

	if (cw)
		seq_printf(s, "current erase block: %u pages used, %u free, "
			"erased %u times\n",
			cwp, d->pages_per_eblk - cwp, cwecount);

	seq_printf(s, "total erasures: %lu\n", sum);

	seq_puts(s, "\n");

	seq_printf(s, "mtdswap_readsect count: %llu\n", d->sect_read_count);
	seq_printf(s, "mtdswap_writesect count: %llu\n", d->sect_write_count);
	seq_printf(s, "mtdswap_discard count: %llu\n", d->discard_count);
	seq_printf(s, "mtd read count: %llu\n", d->mtd_read_count);
	seq_printf(s, "mtd write count: %llu\n", d->mtd_write_count);
	seq_printf(s, "discarded pages count: %llu\n", d->discard_page_count);

	seq_puts(s, "\n");
	seq_printf(s, "total pages: %u\n", pages);
	seq_printf(s, "pages mapped: %u\n", mapped);

	return 0;
}
DEFINE_SHOW_ATTRIBUTE(mtdswap);

static int mtdswap_add_debugfs(struct mtdswap_dev *d)
{
	struct dentry *root = d->mtd->dbg.dfs_dir;
	struct dentry *dent;

	if (!IS_ENABLED(CONFIG_DEBUG_FS))
		return 0;

	if (IS_ERR_OR_NULL(root))
		return -1;

	dent = debugfs_create_file("mtdswap_stats", S_IRUSR, root, d,
				&mtdswap_fops);
	if (!dent) {
		dev_err(d->dev, "debugfs_create_file failed\n");
		return -1;
	}

	return 0;
}

static int mtdswap_init(struct mtdswap_dev *d, unsigned int eblocks,
			unsigned int spare_cnt)
{
	struct mtd_info *mtd = d->mbd_dev->mtd;
	unsigned int i, eblk_bytes, pages, blocks;
	int ret = -ENOMEM;

	d->mtd = mtd;
	d->eblks = eblocks;
	d->spare_eblks = spare_cnt;
	d->pages_per_eblk = mtd->erasesize >> PAGE_SHIFT;

	pages = d->mbd_dev->size;
	blocks = eblocks * d->pages_per_eblk;

	for (i = 0; i < MTDSWAP_TREE_CNT; i++)
		d->trees[i].root = RB_ROOT;

	d->page_data = vmalloc(array_size(pages, sizeof(int)));
	if (!d->page_data)
		goto page_data_fail;

	d->revmap = vmalloc(array_size(blocks, sizeof(int)));
	if (!d->revmap)
		goto revmap_fail;

	eblk_bytes = sizeof(struct swap_eb)*d->eblks;
	d->eb_data = vzalloc(eblk_bytes);
	if (!d->eb_data)
		goto eb_data_fail;

	for (i = 0; i < pages; i++)
		d->page_data[i] = BLOCK_UNDEF;

	for (i = 0; i < blocks; i++)
		d->revmap[i] = PAGE_UNDEF;

	d->page_buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
	if (!d->page_buf)
		goto page_buf_fail;

	if (mtdswap_can_use_oob(mtd)) {
		d->oob_buf = kmalloc_array(2, mtd->oobavail, GFP_KERNEL);
		if (!d->oob_buf)
			goto oob_buf_fail;
	}

	mtdswap_scan_eblks(d);

	return 0;

oob_buf_fail:
	kfree(d->page_buf);
page_buf_fail:
	vfree(d->eb_data);
eb_data_fail:
	vfree(d->revmap);
revmap_fail:
	vfree(d->page_data);
page_data_fail:
	printk(KERN_ERR "%s: init failed (%d)\n", MTDSWAP_PREFIX, ret);
	return ret;
}

static void mtdswap_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
{
	struct mtdswap_dev *d;
	struct mtd_blktrans_dev *mbd_dev;
	char *parts;
	char *this_opt;
	unsigned long part;
	unsigned int eblocks, eavailable, bad_blocks, spare_cnt;
	unsigned int usable_eb_size;
	uint64_t swap_size, use_size, size_limit;
	int ret;

	parts = &partitions[0];
	if (!*parts)
		return;

	while ((this_opt = strsep(&parts, ",")) != NULL) {
		if (kstrtoul(this_opt, 0, &part) < 0)
			return;

		if (mtd->index == part)
			break;
	}

	if (mtd->index != part)
		return;

	/*if (mtd->erasesize < PAGE_SIZE || mtd->erasesize % PAGE_SIZE) {
		printk(KERN_ERR "%s: Erase size %u not multiple of PAGE_SIZE "
			"%lu\n", MTDSWAP_PREFIX, mtd->erasesize, PAGE_SIZE);
		return;
	}*/

	if (PAGE_SIZE % mtd->writesize || mtd->writesize > PAGE_SIZE) {
		printk(KERN_ERR "%s: PAGE_SIZE %lu not multiple of write size"
			" %u\n", MTDSWAP_PREFIX, PAGE_SIZE, mtd->writesize);
		return;
	}

	/*if (!mtd->oobsize || mtd->oobavail < MTDSWAP_OOBSIZE) {
		printk(KERN_ERR "%s: Not enough free bytes in OOB, "
			"%d available, %zu needed.\n",
			MTDSWAP_PREFIX, mtd->oobavail, MTDSWAP_OOBSIZE);
		return;
	}*/

	if (spare_eblocks > 100)
		spare_eblocks = 100;

	use_size = mtd->size;
	size_limit = (uint64_t) BLOCK_MAX * PAGE_SIZE;

	if (mtd->size > size_limit) {
		printk(KERN_WARNING "%s: Device too large. Limiting size to "
			"%llu bytes\n", MTDSWAP_PREFIX, size_limit);
		use_size = size_limit;
	}

	eblocks = mtd_div_by_eb(use_size, mtd);
	usable_eb_size = (mtd->erasesize >> PAGE_SHIFT) << PAGE_SHIFT;
	use_size = (uint64_t)eblocks * mtd->erasesize;
	bad_blocks = mtdswap_badblocks(mtd, use_size);
	eavailable = eblocks - bad_blocks;

	if (eavailable < MIN_ERASE_BLOCKS) {
		printk(KERN_ERR "%s: Not enough erase blocks. %u available, "
			"%d needed\n", MTDSWAP_PREFIX, eavailable,
			MIN_ERASE_BLOCKS);
		return;
	}

	spare_cnt = div_u64((uint64_t)eavailable * spare_eblocks, 100);

	if (spare_cnt < MIN_SPARE_EBLOCKS)
		spare_cnt = MIN_SPARE_EBLOCKS;

	if (spare_cnt > eavailable - 1)
		spare_cnt = eavailable - 1;

	swap_size = (uint64_t)(eavailable - spare_cnt) * usable_eb_size +
		(header ? PAGE_SIZE : 0);

	printk(KERN_INFO "%s: Enabling MTD swap on device %lu, size %llu KB, "
		"%u spare, %u bad blocks\n",
		MTDSWAP_PREFIX, part, swap_size / 1024, spare_cnt, bad_blocks);

	d = kzalloc(sizeof(struct mtdswap_dev), GFP_KERNEL);
	if (!d)
		return;

	mbd_dev = kzalloc(sizeof(struct mtd_blktrans_dev), GFP_KERNEL);
	if (!mbd_dev) {
		kfree(d);
		return;
	}

	d->mbd_dev = mbd_dev;
	mbd_dev->priv = d;

	mbd_dev->mtd = mtd;
	mbd_dev->devnum = mtd->index;
	mbd_dev->size = swap_size >> PAGE_SHIFT;
	mbd_dev->tr = tr;

	if (!(mtd->flags & MTD_WRITEABLE))
		mbd_dev->readonly = 1;

	if (mtdswap_init(d, eblocks, spare_cnt) < 0)
		goto init_failed;

	if (add_mtd_blktrans_dev(mbd_dev) < 0)
		goto cleanup;

	d->dev = disk_to_dev(mbd_dev->disk);

	ret = mtdswap_add_debugfs(d);
	if (ret < 0)
		goto debugfs_failed;

	return;

debugfs_failed:
	del_mtd_blktrans_dev(mbd_dev);

cleanup:
	mtdswap_cleanup(d);

init_failed:
	kfree(mbd_dev);
	kfree(d);
}

static void mtdswap_remove_dev(struct mtd_blktrans_dev *dev)
{
	struct mtdswap_dev *d = MTDSWAP_MBD_TO_MTDSWAP(dev);

	del_mtd_blktrans_dev(dev);
	mtdswap_cleanup(d);
	kfree(d);
}

static struct mtd_blktrans_ops mtdswap_ops = {
	.name		= "mtdswap",
	.major		= 0,
	.part_bits	= 0,
	.blksize	= PAGE_SIZE,
	.flush		= mtdswap_flush,
	.readsect	= mtdswap_readsect,
	.writesect	= mtdswap_writesect,
	.discard	= mtdswap_discard,
	.background	= mtdswap_background,
	.add_mtd	= mtdswap_add_mtd,
	.remove_dev	= mtdswap_remove_dev,
	.owner		= THIS_MODULE,
};

static int __init mtdswap_modinit(void)
{
	return register_mtd_blktrans(&mtdswap_ops);
}

static void __exit mtdswap_modexit(void)
{
	deregister_mtd_blktrans(&mtdswap_ops);
}

module_init(mtdswap_modinit);
module_exit(mtdswap_modexit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Jarkko Lavinen <jarkko.lavinen@nokia.com>");
MODULE_DESCRIPTION("Block device access to an MTD suitable for using as "
		"swap space");

[-- Attachment #3: Type: text/plain, Size: 144 bytes --]

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