Date:	Mon, 17 Jan 2011 14:05:45 +0300
From:	Dmitry <dmonakhov@...nvz.org>
To:	Akira Fujita <a-fujita@...jp.nec.com>, Theodore Tso <tytso@....edu>
Cc:	ext4 development <linux-ext4@...r.kernel.org>
Subject: Re: [RFC][PATCH] ext4: Fix overflow of metadata block reservation counter

On Mon, 17 Jan 2011 17:29:42 +0900, Akira Fujita <a-fujita@...jp.nec.com> wrote:
> Hi,
> 
> The metadata block reservation counter overflows with data write
> on ext4 (indirect block map) when its disk space is almost full.
> This overflow triggers following BUG_ON.
> 
> Jan 14 09:36:48 TNESG9423 kernel: ------------[ cut here ]------------
> Jan 14 09:36:48 TNESG9423 kernel: kernel BUG at fs/ext4/inode.c:2170!
> Jan 14 09:36:48 TNESG9423 kernel: invalid opcode: 0000 [#1] SMP
> Jan 14 09:36:48 TNESG9423 kernel: last sysfs file: /sys/kernel/mm/ksm/run
> Jan 14 09:36:48 TNESG9423 kernel: CPU 0
> Jan 14 09:36:48 TNESG9423 kernel: Modules linked in: ip6table_filter ip6_tables ebtable_nat ebtables xt_CHECKSUM iptable_mangle ipt_MASQUERADE iptable_nat nf_nat nf_conntrack_ipv4 nf_defrag_ipv4
> xt_state nf_conntrack ipt_REJECT bridge stp llc autofs4 sunrpc p4_clockmod freq_table speedstep_lib ipv6 xt_physdev iptable_filter ip_tables nls_utf8 dm_mirror dm_region_hash dm_log dm_mod kvm_intel
> kvm uinput ppdev parport_pc parport sg pcspkr i2c_i801 iTCO_wdt iTCO_vendor_support snd_hda_codec_realtek snd_hda_intel snd_hda_codec snd_hwdep snd_seq snd_seq_device snd_pcm snd_timer snd soundcore
> snd_page_alloc e1000e ext3 jbd sd_mod crc_t10dif sr_mod cdrom pata_via pata_acpi ata_generic ata_piix i915 drm_kms_helper drm i2c_algo_bit i2c_core video output [last unloaded: mperf]
> Jan 14 09:36:48 TNESG9423 kernel:
> Jan 14 09:36:48 TNESG9423 kernel: Pid: 937, comm: flush-8:0 Not tainted 2.6.37 #1 MS-7264BLM/PC-MJ18ABZR4
> Jan 14 09:36:48 TNESG9423 kernel: RIP: 0010:[<ffffffff811c5298>]  [<ffffffff811c5298>] ext4_da_block_invalidatepages+0x168/0x180
> Jan 14 09:36:48 TNESG9423 kernel: RSP: 0018:ffff88007613f780  EFLAGS: 00010246
> Jan 14 09:36:48 TNESG9423 kernel: RAX: 0010000000000024 RBX: 0000000000008cf2 RCX: 000000000000000e
> Jan 14 09:36:48 TNESG9423 kernel: RDX: 000000000000000e RSI: 0000000000000001 RDI: ffffea0000a70d30
> Jan 14 09:36:48 TNESG9423 kernel: RBP: ffff88007613f850 R08: 0000000000000001 R09: 0000000000000002
> Jan 14 09:36:48 TNESG9423 kernel: R10: ffffea0000a70d38 R11: ffff880035f01b58 R12: ffff88007613f7a0
> Jan 14 09:36:48 TNESG9423 kernel: R13: ffff880065eecd68 R14: ffff88007613f7b8 R15: ffffea0000a70a58
> Jan 14 09:36:48 TNESG9423 kernel: FS:  0000000000000000(0000) GS:ffff88007f400000(0000) knlGS:0000000000000000
> Jan 14 09:36:48 TNESG9423 kernel: CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> Jan 14 09:36:48 TNESG9423 kernel: CR2: 0000003680ae1560 CR3: 000000004da45000 CR4: 00000000000006f0
> Jan 14 09:36:48 TNESG9423 kernel: DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> Jan 14 09:36:48 TNESG9423 kernel: DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> Jan 14 09:36:48 TNESG9423 kernel: Process flush-8:0 (pid: 937, threadinfo ffff88007613e000, task ffff8800371b54e0)
> Jan 14 09:36:48 TNESG9423 kernel: Stack:
> Jan 14 09:36:48 TNESG9423 kernel: ffff88007613f7e0 ffffffff814ee3d6 0000000000000008 0000000e7613f7f0
> Jan 14 09:36:48 TNESG9423 kernel: 000000000000000e 000000003741a4b9 ffffea0000a70a58 ffffea0000a70a90
> Jan 14 09:36:48 TNESG9423 kernel: ffffea0000a70ac8 ffffea0000a70b00 ffffea0000a70b38 ffffea0000a70b70
> Jan 14 09:36:48 TNESG9423 kernel: Call Trace:
> Jan 14 09:36:48 TNESG9423 kernel: [<ffffffff814ee3d6>] ? printk+0x41/0x43
> Jan 14 09:36:48 TNESG9423 kernel: [<ffffffff811c9fe4>] mpage_da_map_and_submit+0x274/0x470
> Jan 14 09:36:48 TNESG9423 kernel: [<ffffffff811ca24d>] mpage_add_bh_to_extent+0x6d/0xf0
> Jan 14 09:36:48 TNESG9423 kernel: [<ffffffff811ca5a0>] write_cache_pages_da+0x2d0/0x4a0
> Jan 14 09:36:48 TNESG9423 kernel: [<ffffffff811caa4c>] ext4_da_writepages+0x2dc/0x650
> Jan 14 09:36:48 TNESG9423 kernel: [<ffffffff81105321>] do_writepages+0x21/0x40
> Jan 14 09:36:48 TNESG9423 kernel: [<ffffffff810fb55b>] __filemap_fdatawrite_range+0x5b/0x60
> Jan 14 09:36:48 TNESG9423 kernel: [<ffffffff810fb833>] filemap_fdatawrite_range+0x13/0x20
> Jan 14 09:36:48 TNESG9423 kernel: [<ffffffff811fb6ce>] jbd2_journal_begin_ordered_truncate+0x8e/0xb0
> Jan 14 09:36:48 TNESG9423 kernel: [<ffffffff811cd02b>] ext4_evict_inode+0x23b/0x3b0
> Jan 14 09:36:48 TNESG9423 kernel: [<ffffffff81167477>] evict+0x27/0xc0
> Jan 14 09:36:48 TNESG9423 kernel: [<ffffffff81167a4b>] iput+0x1bb/0x2a0
> Jan 14 09:36:48 TNESG9423 kernel: [<ffffffff811734a4>] writeback_sb_inodes+0x104/0x180
> Jan 14 09:36:48 TNESG9423 kernel: [<ffffffff81173cfd>] writeback_inodes_wb+0x9d/0x160
> Jan 14 09:36:48 TNESG9423 kernel: [<ffffffff8117404b>] wb_writeback+0x28b/0x400
> Jan 14 09:36:48 TNESG9423 kernel: [<ffffffff810714cc>] ? lock_timer_base+0x3c/0x70
> Jan 14 09:36:48 TNESG9423 kernel: [<ffffffff81072092>] ? del_timer_sync+0x22/0x30
> Jan 14 09:36:48 TNESG9423 kernel: [<ffffffff81174257>] wb_do_writeback+0x97/0x1e0
> Jan 14 09:36:48 TNESG9423 kernel: [<ffffffff81174452>] bdi_writeback_thread+0xb2/0x270
> Jan 14 09:36:48 TNESG9423 kernel: [<ffffffff811743a0>] ? bdi_writeback_thread+0x0/0x270
> Jan 14 09:36:48 TNESG9423 kernel: [<ffffffff811743a0>] ? bdi_writeback_thread+0x0/0x270
> Jan 14 09:36:48 TNESG9423 kernel: [<ffffffff81083356>] kthread+0x96/0xa0
> Jan 14 09:36:48 TNESG9423 kernel: [<ffffffff8100ce84>] kernel_thread_helper+0x4/0x10
> Jan 14 09:36:48 TNESG9423 kernel: [<ffffffff810832c0>] ? kthread+0x0/0xa0
> Jan 14 09:36:48 TNESG9423 kernel: [<ffffffff8100ce80>] ? kernel_thread_helper+0x0/0x10
> Jan 14 09:36:48 TNESG9423 kernel: Code: a8 00 00 00 5b 41 5c 41 5d 41 5e 41 5f c9 c3 0f 1f 40 00 4c 89 e7 48 89 95 40 ff ff ff e8 01 1b f4 ff 48 8b 95 40 ff ff ff eb c9 <0f> 0b eb fe 0f 0b 66 90 eb fc
> 66 66 66 66 66 2e 0f 1f 84 00 00
> Jan 14 09:36:48 TNESG9423 kernel: RIP  [<ffffffff811c5298>] ext4_da_block_invalidatepages+0x168/0x180
> Jan 14 09:36:48 TNESG9423 kernel: RSP <ffff88007613f780>
> Jan 14 09:36:48 TNESG9423 kernel: ---[ end trace 0496eaed3b9ec629 ]---
> 
> To fix this, I referred to the patch which is for data blocks
> reservation counter (commit: ef627929781c98113e6ae93f159dd3c12a884ad8)
I cant find that commit in  linus's, and tytso's tries, can you please 
specify where it can be found.
> and made a following patch which prints metadata block inconsistency
> and corrects it.
> My patch is trial, if you have better idea, feel free to fix this bug.
> 
> # You can reproduce this problem with attached programs.
> # In my environment, this occurs in 1 minute.
> 
> Signed-off-by: Akira Fujita <a-fujita@...jp.nec.com>
> ---
>  fs/ext4/inode.c |   10 ++++++++++
>  1 file changed, 10 insertions(+)
> diff -Nrup -X linux-2.6.37-org/Documentation/dontdiff linux-2.6.37-org/fs/ext4/inode.c linux-2.6.37/fs/ext4/inode.c
> --- linux-2.6.37-org/fs/ext4/inode.c	2011-01-17 15:47:59.000000000 +0900
> +++ linux-2.6.37/fs/ext4/inode.c	2011-01-17 15:52:25.000000000 +0900
> @@ -1127,6 +1127,16 @@ void ext4_da_update_reserve_space(struct
>  		used = ei->i_reserved_data_blocks;
>  	}
> 
> +	if (unlikely(ei->i_allocated_meta_blocks >
> +			ei->i_reserved_meta_blocks)) {
> +		ext4_msg(inode->i_sb, KERN_NOTICE, "%s: ino %lu, "
> +			"meta blocks %d with only %d reserved meta blocks\n",
> +			__func__, inode->i_ino, ei->i_allocated_meta_blocks,
> +			ei->i_reserved_meta_blocks);
> +		WARN_ON(1);
> +		ei->i_allocated_meta_blocks = ei->i_reserved_meta_blocks;
> +	}
> +
The situation where allocated > reservation is a very nasty bug and
means what reservation is broken, so next moment result in user data
drop/corruption, due to ENOSPC, so we definitely have to investigate
the root of cause. BTW i cant reproduce the bug with your test 
on 2.6.34.7-63.fc13 which is really old, but still.
Which version should i use to reproduce the issue?
>  	/* Update per-inode reservations */
>  	ei->i_reserved_data_blocks -= used;
>  	ei->i_reserved_meta_blocks -= ei->i_allocated_meta_blocks;
Attachment: metadata_blocks_overflow.sh (application/x-shellscript)
> #include <stdio.h>
> #include <stdlib.h>
> #include <unistd.h>
> #include <string.h>
> #include <sys/file.h>
> #include <sys/mman.h>
> #include <sys/uio.h>
> #include <sys/wait.h>
> #include <errno.h>
> #include <malloc.h>
> 
> #define	BUFSIZE	4096
> #define PATH_MAX 4096
> #define	MINIOSIZE 4*1024
> #define	MAXIOSIZE 4*1024*1024
> 
> #ifndef O_DIRECT
> #define O_DIRECT 040000
> #endif
> 
> static int	bufsize = 0;		/* Buffersize. Default random */
> static int	bufsize_random = 1;	/* Buffersize random flag. Default random */
> static long long	filesize = 0;	/* Target file size */
> static long long	target_range = 0;	/* Target range per process */
> static int	files_num = 0;
> static char	*filenames;
> static int	mmap_write = 0;
> static int	o_sync = 0;
> static int	o_async = 0;
> static int	o_direct = 0;
> 
> static void setup(void);
> static void cleanup(void);
> 
> void prg_usage()
> {
> 	fprintf(stderr, "Usage: fs_write [-S 0|1] [-D] [-n num_process]\n");
> 	fprintf(stderr, "                -s file_size file...\n");
> 	fprintf(stderr, "\n");
> 	fprintf(stderr, "		-S	sync mode (0:O_ASYNC 1:O_SYNC)\n");
> 	fprintf(stderr, "		-D	Direct IO\n");
> 	fprintf(stderr, "		-n	Process count (default is 1)\n");
> 	fprintf(stderr, "		-s	File size\n");
> 	fprintf(stderr, "		file...	Traget file\n");
> 
> 	exit(1);
> }
> 
> int runtest(int fd_w[], int childnum)
> {
> 	int num = 0;
> 	int err = 0;
> 	long long offset = target_range * childnum;
> 	long long  remain = target_range;
> 	int len = bufsize;
> 	int write_len = 0;
> 	int psize = getpagesize();
> 	int max_page = MAXIOSIZE / psize;
> 	char *buf_w;
> 	void *p;
> 
> 	buf_w = (char*)memalign(psize, MAXIOSIZE);
> 
> 	while (remain > 0) {
> 		if (bufsize_random == 1) {
> 			len = (rand() % max_page) * psize;
> 			if (!len)
> 				len = MINIOSIZE;
> 		}
> 		if (len > remain)
> 			len = remain;
> 
> 		for (num = 0; num < files_num ; num++) {
> 			memset(buf_w, childnum+num, len);
> 			if (!mmap_write) {
> 				if (lseek(fd_w[num], offset, SEEK_SET) < 0) {
> 					err = errno;
> 					goto out;
> 				}
> 				if ((write_len = write(fd_w[num], buf_w, len)) < 0) {
> 					err = errno;
> 					goto out;
> 				}
> 				if (len != write_len)
> 					goto out;
> 			} else {
> 				p = mmap(NULL, len, PROT_WRITE, MAP_SHARED,
> 							fd_w[num], offset);
> 				if (p == MAP_FAILED) {
> 					err = errno;
> 					goto out;
> 				}
> 				memcpy(p, buf_w, len);
> 				if (munmap(p, len) == -1) {
> 					err = errno;
> 					goto out;
> 				}
> 			}
> 		}
> 		offset += len;
> 		remain -= len;
> 	}
> 
> out:
> 	if (err == ENOSPC || len != write_len)
> 		err = 0;
> 	if (err > 0)
> 		fprintf(stderr, "%s;\n", strerror(err));
> 	free(buf_w);
> 
> 	return err;
> }
> 
> int child_function(int childnum)
> {
> 	int num, ret = -1;
> 	int fd_w[files_num];
> 	char *filename;
> 	
> 	for (num = 0; num < files_num ; num++) {
> 		fd_w[num] = -1;
> 	}
> 	for (num = 0; num < files_num ; num++) {
> 		filename = filenames + (num*PATH_MAX);
> 		if ((fd_w[num] = open(filename,
> 				O_RDWR|o_sync|o_async|o_direct)) < 0) {
> 			printf("TINFO:fd_w open failed for %s: %s\n",filename, strerror(errno));
> 			goto out;
> 		}
> 	}
> 
> 	ret = runtest(fd_w, childnum);
> 
> out:
> 	for (num = 0; num < files_num ; num++) {
> 		if (fd_w[num] != -1)
> 			close(fd_w[num]);
> 	}
> 
> 	exit(ret);
> }
> 
> static void setup(void)
> {
> 	int num, fd;
> 	char *filename;
> 
> 	for (num = 0; num < files_num; num++) {
> 		filename = filenames + (num * PATH_MAX);
> 		if ((fd = open(filename, O_CREAT|O_EXCL|O_WRONLY|O_TRUNC, 0666)) < 0) {
> 			printf("TBROK, Couldn't create test file %s: %s\n", filename, strerror(errno));
> 			cleanup();
> 		}
> 
> 		if (mmap_write) {
> 			if (ftruncate(fd, filesize) < 0) {
> 				printf("TBROK2: Couldn't create test file %s: %s\n", filename, strerror(errno));
> 				cleanup();
> 			}
> 		}
> 		close(fd);
> 	}
> }
> 
> static void cleanup(void)
> {
> 	int num;
> 	for (num = 0; num < files_num; num++)
> 		unlink(filenames + (num * PATH_MAX));
> 	free(filenames);
> 	exit(1);
> }
> 
> int main(int argc, char *argv[])
> {
> 	int	numchild = 1;	/* Number of children. Default 5 */
> 	int	i, num;
> 	int	err = 0;
> 	int	sync_mode = 0;
> 	int	*cpid;
> 	int 	status;
> 
> 	while ((i = getopt(argc, argv, "MS:Dn:s:")) != -1) {
> 		switch(i) {
> 		case 'M':
> 			mmap_write = 1;
> 			break;
> 		case 'S':
> 			if ((sync_mode = atoi(optarg)) < 0) {
> 				fprintf(stderr, "sync mode must be 0 or 1;\n");
> 				prg_usage();
> 			}
> 			switch (sync_mode) {
> 			case 0:
> 				o_async = O_ASYNC;
> 				break;
> 			case 1:
> 				o_sync = O_SYNC;
> 				break;
> 			default:
> 				fprintf(stderr, "sync mode must be 0 or 1;\n");
> 				prg_usage();
> 			}
> 			break;
> 		case 'D':
> 			o_direct = O_DIRECT;
> 			break;
> 		case 'n':
> 			if ((numchild = atoi(optarg)) <= 0) {
> 				fprintf(stderr, "no of children must be > 0;\n");
> 				prg_usage();
> 			}
> 			break;
> 		case 's':
> 			filesize = atol(optarg);
> 			if (filesize <= 0) {
> 				fprintf(stderr, "filesize must be > 0;\n");
> 				prg_usage();
> 			}
> 			break;
> 		default:
> 			prg_usage();
> 		}
> 	}
> 
> 	files_num = argc - optind;
> 	if (files_num <= 0)
> 		prg_usage();
> 	if (filesize % numchild != 0 || (filesize / numchild) % BUFSIZE != 0) {
> 		fprintf(stderr, "filesize must be multiple of 4k*numchild:"
> 				"filesize=%lld;\n", filesize);
> 		prg_usage();
> 	}
> 
> 	if ((filenames = (char *)malloc(files_num * PATH_MAX)) == NULL ||
> 	    (cpid = (int *)malloc(sizeof(int)*numchild)) == NULL) {
> 		perror("malloc");
> 		exit(1);
> 	}
> 	for(i = optind, num = 0 ; i < argc; i++, num++)
> 		strcpy((char *)filenames + (num * PATH_MAX), argv[i]);
> 	target_range = filesize / numchild;
> 
> 
> 	setup();
> 
> 	for(i = 0; i < numchild; i++) {
> 		*(cpid+i) = fork();
> 		if (*(cpid+i) == 0)
> 			child_function(i);
> 	}
> 	for(i = 0; i < numchild; i++) {
> 		waitpid(*(cpid+1), &status, 0);
> 	}
> 
> 	cleanup();
> 	return err;
> }
--
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