From 8ebc423238341b52912c7295b045a32477b33f09 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Tue, 7 Apr 2009 04:19:49 +0200 Subject: reiserfs: kill-the-BKL This patch is an attempt to remove the Bkl based locking scheme from reiserfs and is intended. It is a bit inspired from an old attempt by Peter Zijlstra: http://lkml.indiana.edu/hypermail/linux/kernel/0704.2/2174.html The bkl is heavily used in this filesystem to prevent from concurrent write accesses on the filesystem. Reiserfs makes a deep use of the specific properties of the Bkl: - It can be acqquired recursively by a same task - It is released on the schedule() calls and reacquired when schedule() returns The two properties above are a roadmap for the reiserfs write locking so it's very hard to simply replace it with a common mutex. - We need a recursive-able locking unless we want to restructure several blocks of the code. - We need to identify the sites where the bkl was implictly relaxed (schedule, wait, sync, etc...) so that we can in turn release and reacquire our new lock explicitly. Such implicit releases of the lock are often required to let other resources producer/consumer do their job or we can suffer unexpected starvations or deadlocks. So the new lock that replaces the bkl here is a per superblock mutex with a specific property: it can be acquired recursively by a same task, like the bkl. For such purpose, we integrate a lock owner and a lock depth field on the superblock information structure. The first axis on this patch is to turn reiserfs_write_(un)lock() function into a wrapper to manage this mutex. Also some explicit calls to lock_kernel() have been converted to reiserfs_write_lock() helpers. The second axis is to find the important blocking sites (schedule...(), wait_on_buffer(), sync_dirty_buffer(), etc...) and then apply an explicit release of the write lock on these locations before blocking. Then we can safely wait for those who can give us resources or those who need some. Typically this is a fight between the current writer, the reiserfs workqueue (aka the async commiter) and the pdflush threads. The third axis is a consequence of the second. The write lock is usually on top of a lock dependency chain which can include the journal lock, the flush lock or the commit lock. So it's dangerous to release and trying to reacquire the write lock while we still hold other locks. This is fine with the bkl: T1 T2 lock_kernel() mutex_lock(A) unlock_kernel() // do something lock_kernel() mutex_lock(A) -> already locked by T1 schedule() (and then unlock_kernel()) lock_kernel() mutex_unlock(A) .... This is not fine with a mutex: T1 T2 mutex_lock(write) mutex_lock(A) mutex_unlock(write) // do something mutex_lock(write) mutex_lock(A) -> already locked by T1 schedule() mutex_lock(write) -> already locked by T2 deadlock The solution in this patch is to provide a helper which releases the write lock and sleep a bit if we can't lock a mutex that depend on it. It's another simulation of the bkl behaviour. The last axis is to locate the fs callbacks that are called with the bkl held, according to Documentation/filesystem/Locking. Those are: - reiserfs_remount - reiserfs_fill_super - reiserfs_put_super Reiserfs didn't need to explicitly lock because of the context of these callbacks. But now we must take care of that with the new locking. After this patch, reiserfs suffers from a slight performance regression (for now). On UP, a high volume write with dd reports an average of 27 MB/s instead of 30 MB/s without the patch applied. Signed-off-by: Frederic Weisbecker Reviewed-by: Ingo Molnar Cc: Jeff Mahoney Cc: Peter Zijlstra Cc: Bron Gondwana Cc: Andrew Morton Cc: Linus Torvalds Cc: Alexander Viro LKML-Reference: <1239070789-13354-1-git-send-email-fweisbec@gmail.com> Signed-off-by: Ingo Molnar --- fs/reiserfs/Makefile | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'fs/reiserfs/Makefile') diff --git a/fs/reiserfs/Makefile b/fs/reiserfs/Makefile index 7c5ab6330dd6..6a9e30c041dd 100644 --- a/fs/reiserfs/Makefile +++ b/fs/reiserfs/Makefile @@ -7,7 +7,7 @@ obj-$(CONFIG_REISERFS_FS) += reiserfs.o reiserfs-objs := bitmap.o do_balan.o namei.o inode.o file.o dir.o fix_node.o \ super.o prints.o objectid.o lbalance.o ibalance.o stree.o \ hashes.o tail_conversion.o journal.o resize.o \ - item_ops.o ioctl.o procfs.o xattr.o + item_ops.o ioctl.o procfs.o xattr.o lock.o ifeq ($(CONFIG_REISERFS_FS_XATTR),y) reiserfs-objs += xattr_user.o xattr_trusted.o -- cgit v1.2.3 From e3c96f53ac132743fda1384910feb863a2eab916 Mon Sep 17 00:00:00 2001 From: Alexey Dobriyan Date: Tue, 15 Dec 2009 16:46:54 -0800 Subject: reiserfs: don't compile procfs.o at all if no support * small define cleanup in header * fix #ifdeffery in procfs.c via Kconfig Signed-off-by: Alexey Dobriyan Cc: Jeff Mahoney Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/reiserfs/Makefile | 6 +++++- fs/reiserfs/procfs.c | 26 -------------------------- include/linux/reiserfs_fs.h | 30 +++++++++++++++++++++--------- 3 files changed, 26 insertions(+), 36 deletions(-) (limited to 'fs/reiserfs/Makefile') diff --git a/fs/reiserfs/Makefile b/fs/reiserfs/Makefile index 6a9e30c041dd..792b3cb2cd18 100644 --- a/fs/reiserfs/Makefile +++ b/fs/reiserfs/Makefile @@ -7,7 +7,11 @@ obj-$(CONFIG_REISERFS_FS) += reiserfs.o reiserfs-objs := bitmap.o do_balan.o namei.o inode.o file.o dir.o fix_node.o \ super.o prints.o objectid.o lbalance.o ibalance.o stree.o \ hashes.o tail_conversion.o journal.o resize.o \ - item_ops.o ioctl.o procfs.o xattr.o lock.o + item_ops.o ioctl.o xattr.o lock.o + +ifeq ($(CONFIG_REISERFS_PROC_INFO),y) +reiserfs-objs += procfs.o +endif ifeq ($(CONFIG_REISERFS_FS_XATTR),y) reiserfs-objs += xattr_user.o xattr_trusted.o diff --git a/fs/reiserfs/procfs.c b/fs/reiserfs/procfs.c index 0ebb11646526..7a9981196c1c 100644 --- a/fs/reiserfs/procfs.c +++ b/fs/reiserfs/procfs.c @@ -17,8 +17,6 @@ #include #include -#ifdef CONFIG_REISERFS_PROC_INFO - /* * LOCKING: * @@ -551,30 +549,6 @@ int reiserfs_proc_info_global_done(void) } return 0; } - -/* REISERFS_PROC_INFO */ -#else - -int reiserfs_proc_info_init(struct super_block *sb) -{ - return 0; -} -int reiserfs_proc_info_done(struct super_block *sb) -{ - return 0; -} - -int reiserfs_proc_info_global_init(void) -{ - return 0; -} -int reiserfs_proc_info_global_done(void) -{ - return 0; -} -/* REISERFS_PROC_INFO */ -#endif - /* * Revision 1.1.8.2 2001/07/15 17:08:42 god * . use get_super() in procfs.c diff --git a/include/linux/reiserfs_fs.h b/include/linux/reiserfs_fs.h index f65ed0d3a920..c96c1858fe2c 100644 --- a/include/linux/reiserfs_fs.h +++ b/include/linux/reiserfs_fs.h @@ -2051,21 +2051,13 @@ void set_de_name_and_namelen(struct reiserfs_dir_entry *de); int search_by_entry_key(struct super_block *sb, const struct cpu_key *key, struct treepath *path, struct reiserfs_dir_entry *de); struct dentry *reiserfs_get_parent(struct dentry *); -/* procfs.c */ - -#if defined( CONFIG_PROC_FS ) && defined( CONFIG_REISERFS_PROC_INFO ) -#define REISERFS_PROC_INFO -#else -#undef REISERFS_PROC_INFO -#endif +#ifdef CONFIG_REISERFS_PROC_INFO int reiserfs_proc_info_init(struct super_block *sb); int reiserfs_proc_info_done(struct super_block *sb); int reiserfs_proc_info_global_init(void); int reiserfs_proc_info_global_done(void); -#if defined( REISERFS_PROC_INFO ) - #define PROC_EXP( e ) e #define __PINFO( sb ) REISERFS_SB(sb) -> s_proc_info_data @@ -2079,6 +2071,26 @@ int reiserfs_proc_info_global_done(void); PROC_INFO_ADD( sb, free_at[ ( level ) ], B_FREE_SPACE( bh ) ); \ PROC_INFO_ADD( sb, items_at[ ( level ) ], B_NR_ITEMS( bh ) ) #else +static inline int reiserfs_proc_info_init(struct super_block *sb) +{ + return 0; +} + +static inline int reiserfs_proc_info_done(struct super_block *sb) +{ + return 0; +} + +static inline int reiserfs_proc_info_global_init(void) +{ + return 0; +} + +static inline int reiserfs_proc_info_global_done(void) +{ + return 0; +} + #define PROC_EXP( e ) #define VOID_V ( ( void ) 0 ) #define PROC_INFO_MAX( sb, field, value ) VOID_V -- cgit v1.2.3