Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756565AbZCJOiY (ORCPT ); Tue, 10 Mar 2009 10:38:24 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755852AbZCJOiI (ORCPT ); Tue, 10 Mar 2009 10:38:08 -0400 Received: from cantor.suse.de ([195.135.220.2]:46027 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752442AbZCJOiF (ORCPT ); Tue, 10 Mar 2009 10:38:05 -0400 Date: Tue, 10 Mar 2009 15:38:01 +0100 From: Nick Piggin To: Linux Kernel Mailing List , linux-fsdevel@vger.kernel.org, Andrew Morton , Dave Hansen Subject: [patch 2/2] fs: introduce mnt_clone_write Message-ID: <20090310143801.GC15977@wotan.suse.de> References: <20090310143718.GB15977@wotan.suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090310143718.GB15977@wotan.suse.de> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5478 Lines: 173 fs: introduce mnt_clone_write This patch speeds up lmbench lat_mmap test by about another 2% after the first patch. Before: avg = 462.286 std = 5.46106 After: avg = 453.12 std = 9.58257 (50 runs of each, stddev gives a reasonable confidence) It does this by introducing mnt_clone_write, which avoids some heavyweight operations of mnt_want_write if called on a vfsmount which we know already has a write count; and mnt_want_write_file, which can call mnt_clone_write if the file is open for write. After these two patches, mnt_want_write and mnt_drop_write go from 7% on the profile down to 1.3% (including mnt_clone_write). Cc: Dave Hansen Signed-off-by: Nick Piggin --- fs/file_table.c | 3 +-- fs/inode.c | 2 +- fs/namespace.c | 38 ++++++++++++++++++++++++++++++++++++++ fs/open.c | 4 ++-- fs/xattr.c | 4 ++-- include/linux/mount.h | 2 ++ 6 files changed, 46 insertions(+), 7 deletions(-) Index: linux-2.6/fs/file_table.c =================================================================== --- linux-2.6.orig/fs/file_table.c +++ linux-2.6/fs/file_table.c @@ -213,8 +213,7 @@ int init_file(struct file *file, struct */ if ((mode & FMODE_WRITE) && !special_file(dentry->d_inode->i_mode)) { file_take_write(file); - error = mnt_want_write(mnt); - WARN_ON(error); + mnt_clone_write(mnt); } return error; } Index: linux-2.6/fs/inode.c =================================================================== --- linux-2.6.orig/fs/inode.c +++ linux-2.6/fs/inode.c @@ -1362,7 +1362,7 @@ void file_update_time(struct file *file) if (IS_NOCMTIME(inode)) return; - err = mnt_want_write(file->f_path.mnt); + err = mnt_want_write_file(file->f_path.mnt, file); if (err) return; Index: linux-2.6/fs/namespace.c =================================================================== --- linux-2.6.orig/fs/namespace.c +++ linux-2.6/fs/namespace.c @@ -264,6 +264,44 @@ out: EXPORT_SYMBOL_GPL(mnt_want_write); /** + * mnt_clone_write - get write access to a mount + * @mnt: the mount on which to take a write + * + * This is effectively like mnt_want_write, except + * it must only be used to take an extra write reference + * on a mountpoint that we already know has a write reference + * on it. This allows some optimisation. + * + * After finished, mnt_drop_write must be called as usual to + * drop the reference. + */ +void mnt_clone_write(struct vfsmount *mnt) +{ + preempt_disable(); + inc_mnt_writers(mnt); + preempt_enable(); +} +EXPORT_SYMBOL_GPL(mnt_clone_write); + +/** + * mnt_want_write_file - get write access to a file's mount + * @file: the file who's mount on which to take a write + * + * This is like mnt_want_write, but it takes a file and can + * do some optimisations if the file is open for write already + */ +int mnt_want_write_file(struct vfsmount *mnt, struct file *file) +{ + if (!(file->f_mode & FMODE_WRITE)) + return mnt_want_write(mnt); + else { + mnt_clone_write(mnt); + return 0; + } +} +EXPORT_SYMBOL_GPL(mnt_want_write_file); + +/** * mnt_drop_write - give up write access to a mount * @mnt: the mount on which to give up write access * Index: linux-2.6/fs/open.c =================================================================== --- linux-2.6.orig/fs/open.c +++ linux-2.6/fs/open.c @@ -611,7 +611,7 @@ SYSCALL_DEFINE2(fchmod, unsigned int, fd audit_inode(NULL, dentry); - err = mnt_want_write(file->f_path.mnt); + err = mnt_want_write_file(file->f_path.mnt, file); if (err) goto out_putf; mutex_lock(&inode->i_mutex); @@ -760,7 +760,7 @@ SYSCALL_DEFINE3(fchown, unsigned int, fd if (!file) goto out; - error = mnt_want_write(file->f_path.mnt); + error = mnt_want_write_file(file->f_path.mnt, file); if (error) goto out_fput; dentry = file->f_path.dentry; Index: linux-2.6/fs/xattr.c =================================================================== --- linux-2.6.orig/fs/xattr.c +++ linux-2.6/fs/xattr.c @@ -301,7 +301,7 @@ SYSCALL_DEFINE5(fsetxattr, int, fd, cons return error; dentry = f->f_path.dentry; audit_inode(NULL, dentry); - error = mnt_want_write(f->f_path.mnt); + error = mnt_want_write_file(f->f_path.mnt, f); if (!error) { error = setxattr(dentry, name, value, size, flags); mnt_drop_write(f->f_path.mnt); @@ -528,7 +528,7 @@ SYSCALL_DEFINE2(fremovexattr, int, fd, c return error; dentry = f->f_path.dentry; audit_inode(NULL, dentry); - error = mnt_want_write(f->f_path.mnt); + error = mnt_want_write_file(f->f_path.mnt, f); if (!error) { error = removexattr(dentry, name); mnt_drop_write(f->f_path.mnt); Index: linux-2.6/include/linux/mount.h =================================================================== --- linux-2.6.orig/include/linux/mount.h +++ linux-2.6/include/linux/mount.h @@ -89,6 +89,8 @@ static inline struct vfsmount *mntget(st } extern int mnt_want_write(struct vfsmount *mnt); +extern int mnt_want_write_file(struct vfsmount *mnt, struct file *file); +extern void mnt_clone_write(struct vfsmount *mnt); extern void mnt_drop_write(struct vfsmount *mnt); extern void mntput_no_expire(struct vfsmount *mnt); extern void mnt_pin(struct vfsmount *mnt); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/