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Message-ID: <20130801212405.GD31857@quack.suse.cz> Date: Thu, 1 Aug 2013 23:24:05 +0200 From: Jan Kara <jack@...e.cz> To: Paul Gortmaker <paul.gortmaker@...driver.com> Cc: Jan Kara <jack@...e.cz>, Andrew Morton <akpm@...ux-foundation.org>, linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH 1/4] jbd: use module parameters instead of debugfs for jbd_debug On Thu 01-08-13 15:01:05, Paul Gortmaker wrote: > This is a direct backport of commit b6e96d0067d81f6a300bedee > ("jbd2: use module parameters instead of debugfs for jbd_debug") > from jbd2 into jbd. The value is in making ext4 and ext3 user > experiences consistent with each other. Quoting the original: > > -------------- > There are multiple reasons to move away from debugfs. First of all, > we are only using it for a single parameter, and it is much more > complicated to set up (some 30 lines of code compared to 3), and one > more thing that might fail while loading the jbd2 module. > > Secondly, as a module paramter it can be specified as a boot option if > jbd2 is built into the kernel, or as a parameter when the module is > loaded, and it can also be manipulated dynamically under > /sys/module/jbd2/parameters/jbd2_debug. So it is more flexible. > > Ultimately we want to move away from using jbd_debug() towards > tracepoints, but for now this is still a useful simplification of the > code base. > -------------- > > It is worth noting that we use /sys/module/jbd/parameters/jbd1_debug > (i.e. the "1" might appear odd) for the module parameter in order to > avoid namespace collisions with the existing jbd_debug used as a > function call. > > In addition, we combine the content of jbd2 commit 75497d0607b56e16e4 > ("jbd2: remove debug dependency on debug_fs and update Kconfig help text") > since they were only separate commits unintentionally in jbd2. Thanks for the patch but is jbd_debug really worth it - especially with the somewhat ugly jbd1_debug? I don't thing anybody besides kernel developers really uses it and those can figure how to do what they need... Honza > > Signed-off-by: Paul Gortmaker <paul.gortmaker@...driver.com> > --- > fs/jbd/Kconfig | 6 +++--- > fs/jbd/journal.c | 49 ++++++++----------------------------------------- > include/linux/jbd.h | 3 +-- > 3 files changed, 12 insertions(+), 46 deletions(-) > > diff --git a/fs/jbd/Kconfig b/fs/jbd/Kconfig > index 4e28bee..54cbb55 100644 > --- a/fs/jbd/Kconfig > +++ b/fs/jbd/Kconfig > @@ -15,7 +15,7 @@ config JBD > > config JBD_DEBUG > bool "JBD (ext3) debugging support" > - depends on JBD && DEBUG_FS > + depends on JBD > help > If you are using the ext3 journaled file system (or potentially any > other file system/device using JBD), this option allows you to > @@ -24,7 +24,7 @@ config JBD_DEBUG > debugging output will be turned off. > > If you select Y here, then you will be able to turn on debugging > - with "echo N > /sys/kernel/debug/jbd/jbd-debug", where N is a > + with "echo N > /sys/module/jbd/parameters/jbd1_debug", where N is a > number between 1 and 5, the higher the number, the more debugging > output is generated. To turn debugging off again, do > - "echo 0 > /sys/kernel/debug/jbd/jbd-debug". > + "echo 0 > /sys/module/jbd/parameters/jbd1_debug". > diff --git a/fs/jbd/journal.c b/fs/jbd/journal.c > index 6510d63..166263d 100644 > --- a/fs/jbd/journal.c > +++ b/fs/jbd/journal.c > @@ -35,7 +35,6 @@ > #include <linux/kthread.h> > #include <linux/poison.h> > #include <linux/proc_fs.h> > -#include <linux/debugfs.h> > #include <linux/ratelimit.h> > > #define CREATE_TRACE_POINTS > @@ -44,6 +43,14 @@ > #include <asm/uaccess.h> > #include <asm/page.h> > > +#ifdef CONFIG_JBD_DEBUG > +ushort jbd_journal_enable_debug __read_mostly; > +EXPORT_SYMBOL(jbd_journal_enable_debug); > + > +module_param_named(jbd1_debug, jbd_journal_enable_debug, ushort, 0644); > +MODULE_PARM_DESC(jbd1_debug, "Debugging level for jbd"); > +#endif > + > EXPORT_SYMBOL(journal_start); > EXPORT_SYMBOL(journal_restart); > EXPORT_SYMBOL(journal_extend); > @@ -2017,44 +2024,6 @@ void journal_put_journal_head(struct journal_head *jh) > jbd_unlock_bh_journal_head(bh); > } > > -/* > - * debugfs tunables > - */ > -#ifdef CONFIG_JBD_DEBUG > - > -u8 journal_enable_debug __read_mostly; > -EXPORT_SYMBOL(journal_enable_debug); > - > -static struct dentry *jbd_debugfs_dir; > -static struct dentry *jbd_debug; > - > -static void __init jbd_create_debugfs_entry(void) > -{ > - jbd_debugfs_dir = debugfs_create_dir("jbd", NULL); > - if (jbd_debugfs_dir) > - jbd_debug = debugfs_create_u8("jbd-debug", S_IRUGO | S_IWUSR, > - jbd_debugfs_dir, > - &journal_enable_debug); > -} > - > -static void __exit jbd_remove_debugfs_entry(void) > -{ > - debugfs_remove(jbd_debug); > - debugfs_remove(jbd_debugfs_dir); > -} > - > -#else > - > -static inline void jbd_create_debugfs_entry(void) > -{ > -} > - > -static inline void jbd_remove_debugfs_entry(void) > -{ > -} > - > -#endif > - > struct kmem_cache *jbd_handle_cache; > > static int __init journal_init_handle_cache(void) > @@ -2109,7 +2078,6 @@ static int __init journal_init(void) > ret = journal_init_caches(); > if (ret != 0) > journal_destroy_caches(); > - jbd_create_debugfs_entry(); > return ret; > } > > @@ -2120,7 +2088,6 @@ static void __exit journal_exit(void) > if (n) > printk(KERN_EMERG "JBD: leaked %d journal_heads!\n", n); > #endif > - jbd_remove_debugfs_entry(); > journal_destroy_caches(); > } > > diff --git a/include/linux/jbd.h b/include/linux/jbd.h > index 8685d1b..e45b430 100644 > --- a/include/linux/jbd.h > +++ b/include/linux/jbd.h > @@ -20,7 +20,6 @@ > #ifndef __KERNEL__ > #include "jfs_compat.h" > #define JFS_DEBUG > -#define jfs_debug jbd_debug > #else > > #include <linux/types.h> > @@ -55,7 +54,7 @@ > * CONFIG_JBD_DEBUG is on. > */ > #define JBD_EXPENSIVE_CHECKING > -extern u8 journal_enable_debug; > +extern ushort journal_enable_debug; > > #define jbd_debug(n, f, a...) \ > do { \ > -- > 1.8.1.2 > -- Jan Kara <jack@...e.cz> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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