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Date: Mon, 6 Jun 2011 17:08:08 +0200 (CEST)
From: Lukas Czerner <lczerner@...hat.com>
To: amir73il@...rs.sourceforge.net
cc: linux-ext4@...r.kernel.org, tytso@....edu,
Amir Goldstein <amir73il@...rs.sf.net>,
Yongqiang Yang <xiaoqiangnk@...il.com>
Subject: Re: [PATCH RFC 02/30] ext4: snapshot debugging support
On Mon, 9 May 2011, amir73il@...rs.sourceforge.net wrote:
> From: Amir Goldstein <amir73il@...rs.sf.net>
>
> Control snapshot debug level via debugfs entry /ext4/snapshot-debug
> and induce delay tests via debugfs entries /ext4/test-XXX-delay-msec.
Wouldn't you rather consider adding fixed tracepoints ? I think
tracepoints would be useful regardless on this debufs interface.
>
> Signed-off-by: Amir Goldstein <amir73il@...rs.sf.net>
> Signed-off-by: Yongqiang Yang <xiaoqiangnk@...il.com>
> ---
> fs/ext4/Makefile | 1 +
> fs/ext4/mballoc.c | 3 +
> fs/ext4/snapshot.h | 9 ++++
> fs/ext4/snapshot_debug.h | 105 ++++++++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 118 insertions(+), 0 deletions(-)
>
> diff --git a/fs/ext4/Makefile b/fs/ext4/Makefile
> index 16a779d..9981306 100644
> --- a/fs/ext4/Makefile
> +++ b/fs/ext4/Makefile
> @@ -21,3 +21,4 @@ ext4-$(CONFIG_EXT4_FS_POSIX_ACL) += acl.o
> ext4-$(CONFIG_EXT4_FS_SECURITY) += xattr_security.o
> ext4-$(CONFIG_EXT4_FS_SNAPSHOT) += snapshot.o snapshot_ctl.o
> ext4-$(CONFIG_EXT4_FS_SNAPSHOT) += snapshot_inode.o snapshot_buffer.o
> +ext4-$(CONFIG_EXT4_FS_SNAPSHOT) += snapshot_debug.o
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index 4952b7b..42961bf 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -2657,10 +2657,13 @@ static void __init ext4_create_debugfs_entry(void)
> S_IRUGO | S_IWUSR,
> debugfs_dir,
> &mb_enable_debug);
> + if (debugfs_dir)
> + ext4_snapshot_create_debugfs_entry(debugfs_dir);
> }
>
> static void ext4_remove_debugfs_entry(void)
> {
> + ext4_snapshot_remove_debugfs_entry();
I do not see it defined anywhere.
> debugfs_remove(debugfs_debug);
> debugfs_remove(debugfs_dir);
> }
> diff --git a/fs/ext4/snapshot.h b/fs/ext4/snapshot.h
> index a927090..52bfa52 100644
> --- a/fs/ext4/snapshot.h
> +++ b/fs/ext4/snapshot.h
> @@ -18,6 +18,7 @@
> #include <linux/version.h>
> #include <linux/delay.h>
> #include "ext4.h"
> +#include "snapshot_debug.h"
>
>
> /*
> @@ -109,6 +110,14 @@
> static inline void snapshot_size_extend(struct inode *inode,
> ext4_fsblk_t blocks)
> {
> +#ifdef CONFIG_EXT4_DEBUG
> + ext4_fsblk_t old_blocks = SNAPSHOT_PROGRESS(inode);
> + ext4_fsblk_t max_blocks = SNAPSHOT_BLOCKS(inode);
> +
> + /* sleep total of tunable delay unit over 100% progress */
What is this good for, it is not clear from the description.
> + snapshot_test_delay_progress(SNAPTEST_DELETE,
> + old_blocks, blocks, max_blocks);
> +#endif
> i_size_write((inode), (loff_t)(blocks) << SNAPSHOT_BLOCK_SIZE_BITS);
> }
>
> diff --git a/fs/ext4/snapshot_debug.h b/fs/ext4/snapshot_debug.h
> index e69de29..f893eb1 100644
> --- a/fs/ext4/snapshot_debug.h
> +++ b/fs/ext4/snapshot_debug.h
> @@ -0,0 +1,105 @@
> +/*
> + * linux/fs/ext4/snapshot_debug.h
> + *
> + * Written by Amir Goldstein <amir73il@...rs.sf.net>, 2008
> + *
> + * Copyright (C) 2008-2011 CTERA Networks
> + *
> + * This file is part of the Linux kernel and is made available under
> + * the terms of the GNU General Public License, version 2, or at your
> + * option, any later version, incorporated herein by reference.
> + *
> + * Ext4 snapshot debugging.
> + */
> +
> +#ifndef _LINUX_EXT4_SNAPSHOT_DEBUG_H
> +#define _LINUX_EXT4_SNAPSHOT_DEBUG_H
> +
> +#if defined(CONFIG_EXT4_FS_SNAPSHOT) && defined(CONFIG_EXT4_DEBUG)
> +#include <linux/delay.h>
> +
> +#define SNAPSHOT_INDENT_MAX 4
> +#define SNAPSHOT_INDENT_STR "\t\t\t\t"
> +
> +#define SNAPTEST_TAKE 0
> +#define SNAPTEST_DELETE 1
> +#define SNAPTEST_COW 2
> +#define SNAPTEST_READ 3
> +#define SNAPTEST_BITMAP 4
> +#define SNAPSHOT_TESTS_NUM 5
> +
> +extern const char *snapshot_indent;
> +extern u8 snapshot_enable_debug;
> +extern u16 snapshot_enable_test[SNAPSHOT_TESTS_NUM];
> +extern u8 cow_cache_enabled;
> +
> +#define snapshot_test_delay(i) \
> + do { \
> + if (snapshot_enable_test[i]) \
> + msleep_interruptible(snapshot_enable_test[i]); \
> + } while (0)
> +
> +/*
> + * Sleep 1ms every 'blocks_per_ms', amounting to the total test delay
> + * over 100% of progress (when 'to' reaches 'max').
> + * snapshot_enable_test[i] (msec) is limited to 64K and max (blocks_count)
> + * is likely much more than 64K, so 'blocks_per_ms' is likely non zero.
> + */
Oh, here is a good place for explaining the purpose.
> +#define snapshot_test_delay_progress(i, from, to, max) \
> + do { \
> + if (snapshot_enable_test[i] && \
> + (max) > snapshot_enable_test[i] && \
> + (from) <= (to) && (to) <= (max)) { \
> + unsigned long blocks_per_ms = \
> + do_div((max), snapshot_enable_test[i]); \
> + unsigned long x = do_div((from), blocks_per_ms);\
> + unsigned long y = do_div((to), blocks_per_ms); \
> + if (y > x) \
> + msleep_interruptible(y - x); \
> + } \
> + } while (0)
> +
> +#define snapshot_debug_l(n, l, f, a...) \
> + do { \
> + if ((n) <= snapshot_enable_debug && \
> + (l) <= SNAPSHOT_INDENT_MAX) { \
> + printk(KERN_DEBUG "snapshot: %s" f, \
> + snapshot_indent - (l), \
> + ## a); \
> + } \
> + } while (0)
This can be done by tracepoints maybe ?
> +
> +#define snapshot_debug(n, f, a...) snapshot_debug_l(n, 0, f, ## a)
> +
> +#define snapshot_debug_once(n, f, a...) \
formating
> + do { \
> + static bool __once; \
> + if (!__once) { \
> + snapshot_debug(n, f, ## a); \
> + __once = true; \
> + } \
> + } while (0)
> +
> +extern void ext4_snapshot_create_debugfs_entry(struct dentry *debugfs_dir);
> +extern void ext4_snapshot_remove_debugfs_entry(void);
> +
> +#else
> +#define snapshot_enable_debug (0)
> +#define snapshot_test_delay(i)
> +#define snapshot_test_delay_progress(i, from, to, max)
> +#define snapshot_debug(n, f, a...)
> +#define snapshot_debug_l(n, l, f, a...)
> +#define snapshot_debug_once(n, f, a...)
> +#define ext4_snapshot_create_debugfs_entry(d)
> +#define ext4_snapshot_remove_debugfs_entry()
> +#endif
> +
> +
> +/* debug levels */
> +#define SNAP_ERR 1 /* errors and summary */
> +#define SNAP_WARN 2 /* warnings */
It seems to me that those two levels should be displayed no matter what
via standard functions.
> +#define SNAP_INFO 3 /* info */
> +#define SNAP_DEBUG 4 /* debug */
And this two levels can be done in tracepoints.
> +#define SNAP_DUMP 5 /* dump snapshot file */
Via e2fsprogs debugfs maybe ?
> +
> +#endif /* _LINUX_EXT4_SNAPSHOT_DEBUG_H */
>
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