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authornpiggin@suse.de <npiggin@suse.de>2009-04-26 20:25:55 +1000
committerAl Viro <viro@zeniv.linux.org.uk>2009-06-11 21:36:02 -0400
commit96029c4e09ccbd73a6d0ed2b29e80bf2586ad7ef (patch)
tree032d2ac7024250c18487a2c7122af68fe56567ff
parentd3ef3d7351ccfbef3e5d926efc5ee332136f40d4 (diff)
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). [AV: mnt_want_write_file() should take file alone and derive mnt from it; not only all callers have that form, but that's the only mnt about which we know that it's already held for write if file is opened for write] Cc: Dave Hansen <haveblue@us.ibm.com> Signed-off-by: Nick Piggin <npiggin@suse.de> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
-rw-r--r--fs/file_table.c2
-rw-r--r--fs/inode.c2
-rw-r--r--fs/namespace.c40
-rw-r--r--fs/open.c4
-rw-r--r--fs/xattr.c4
-rw-r--r--include/linux/mount.h4
6 files changed, 50 insertions, 6 deletions
diff --git a/fs/file_table.c b/fs/file_table.c
index 54018fe4884..3d66dbcebef 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -214,7 +214,7 @@ int init_file(struct file *file, struct vfsmount *mnt, struct dentry *dentry,
*/
if ((mode & FMODE_WRITE) && !special_file(dentry->d_inode->i_mode)) {
file_take_write(file);
- error = mnt_want_write(mnt);
+ error = mnt_clone_write(mnt);
WARN_ON(error);
}
return error;
diff --git a/fs/inode.c b/fs/inode.c
index ca337014ae2..a88baebf77c 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1422,7 +1422,7 @@ 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);
if (err)
return;
diff --git a/fs/namespace.c b/fs/namespace.c
index 22ae06ad751..120b8a6b99e 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -265,6 +265,46 @@ 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.
+ */
+int mnt_clone_write(struct vfsmount *mnt)
+{
+ /* superblock may be r/o */
+ if (__mnt_is_readonly(mnt))
+ return -EROFS;
+ preempt_disable();
+ inc_mnt_writers(mnt);
+ preempt_enable();
+ return 0;
+}
+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 file *file)
+{
+ if (!(file->f_mode & FMODE_WRITE))
+ return mnt_want_write(file->f_path.mnt);
+ else
+ return mnt_clone_write(file->f_path.mnt);
+}
+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
*
diff --git a/fs/open.c b/fs/open.c
index bdfbf03615a..7200e23d925 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -612,7 +612,7 @@ SYSCALL_DEFINE2(fchmod, unsigned int, fd, mode_t, mode)
audit_inode(NULL, dentry);
- err = mnt_want_write(file->f_path.mnt);
+ err = mnt_want_write_file(file);
if (err)
goto out_putf;
mutex_lock(&inode->i_mutex);
@@ -761,7 +761,7 @@ SYSCALL_DEFINE3(fchown, unsigned int, fd, uid_t, user, gid_t, group)
if (!file)
goto out;
- error = mnt_want_write(file->f_path.mnt);
+ error = mnt_want_write_file(file);
if (error)
goto out_fput;
dentry = file->f_path.dentry;
diff --git a/fs/xattr.c b/fs/xattr.c
index d51b8f9db92..1c3d0af59dd 100644
--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -297,7 +297,7 @@ SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
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);
if (!error) {
error = setxattr(dentry, name, value, size, flags);
mnt_drop_write(f->f_path.mnt);
@@ -524,7 +524,7 @@ SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
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);
if (!error) {
error = removexattr(dentry, name);
mnt_drop_write(f->f_path.mnt);
diff --git a/include/linux/mount.h b/include/linux/mount.h
index ac49c1f8e5c..5d527536486 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -88,7 +88,11 @@ static inline struct vfsmount *mntget(struct vfsmount *mnt)
return mnt;
}
+struct file; /* forward dec */
+
extern int mnt_want_write(struct vfsmount *mnt);
+extern int mnt_want_write_file(struct file *file);
+extern int 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);