Hi Andrew
I am sorry, my previous patch had a /proc/*/fd/ in a comment, so the */ closed
the comment and fs/dcache.c could not compile.
Could you please put this 'final-final' version in mm for testing ?
Thank's to all contributors, sorry for the noise.
[PATCH] VFS : Delay the dentry name generation on sockets and pipes.
1) Introduces a new method in 'struct dentry_operations'. This method called
d_dname() might be called from d_path() to build a pathname
for special filesystems. It is called without locks.
Future patches (if we succeed in having one common dentry for all
pipes/sockets) may need to change prototype of this method, but we now use :
char *d_dname(struct dentry *dentry, char *buffer, int buflen);
2) Use this new method for sockets : No more sprintf() at socket creation.
This is delayed up to the moment someone does an access to /proc/pid/fd/...
3) Use this new method for pipes : No more sprintf() at pipe creation. This is
delayed up to the moment someone does an access to /proc/pid/fd/...
A benchmark consisting of 1.000.000 calls to pipe()/close()/close() gives a
*nice* speedup on my Pentium(M) 1.6 Ghz :
3.090 s instead of 3.450 s
Signed-off-by: Eric Dumazet <[EMAIL PROTECTED]>
Acked-by: Christoph Hellwig <[EMAIL PROTECTED]>
Acked-by: Linus Torvalds <[EMAIL PROTECTED]>
Documentation/filesystems/Locking | 2 ++
Documentation/filesystems/vfs.txt | 12 +++++++++++-
fs/dcache.c | 10 ++++++++++
fs/pipe.c | 15 +++++++++------
include/linux/dcache.h | 1 +
net/socket.c | 17 ++++++++++-------
6 files changed, 43 insertions(+), 14 deletions(-)
--- linux-2.6.21-rc3/include/linux/dcache.h 2007-03-07 17:23:55.000000000
+0100
+++ linux-2.6.21-rc3-ed/include/linux/dcache.h 2007-03-08 11:57:41.000000000
+0100
@@ -133,6 +133,7 @@ struct dentry_operations {
int (*d_delete)(struct dentry *);
void (*d_release)(struct dentry *);
void (*d_iput)(struct dentry *, struct inode *);
+ char *(*d_dname)(struct dentry *, char *, int);
};
/* the dentry parameter passed to d_hash and d_compare is the parent
--- linux-2.6.21-rc3/Documentation/filesystems/vfs.txt 2007-03-08
10:14:38.000000000 +0100
+++ linux-2.6.21-rc3-ed/Documentation/filesystems/vfs.txt 2007-03-08
12:08:56.000000000 +0100
@@ -827,7 +827,7 @@ This describes how a filesystem can over
operations. Dentries and the dcache are the domain of the VFS and the
individual filesystem implementations. Device drivers have no business
here. These methods may be set to NULL, as they are either optional or
-the VFS uses a default. As of kernel 2.6.13, the following members are
+the VFS uses a default. As of kernel 2.6.22, the following members are
defined:
struct dentry_operations {
@@ -837,6 +837,7 @@ struct dentry_operations {
int (*d_delete)(struct dentry *);
void (*d_release)(struct dentry *);
void (*d_iput)(struct dentry *, struct inode *);
+ char *(*d_dname)(struct dentry *, char *, int);
};
d_revalidate: called when the VFS needs to revalidate a dentry. This
@@ -859,6 +860,15 @@ struct dentry_operations {
VFS calls iput(). If you define this method, you must call
iput() yourself
+ d_dname: called when the pathname of a dentry should be generated.
+ Usefull for some pseudo filesystems (sockfs, pipefs, ...) to delay
+ pathname generation. (Instead of doing it when dentry is created,
+ its done only when the path is needed.). Real filesystems probably
+ dont want to use it, because their dentries are present in global
+ dcache hash, so their hash should be an invariant. As no lock is
+ held, d_dname() should not try to modify the dentry itself, unless
+ appropriate SMP safety is used.
+
Each dentry has a pointer to its parent dentry, as well as a hash list
of child dentries. Child dentries are basically like files in a
directory.
--- linux-2.6.21-rc3/Documentation/filesystems/Locking 2007-03-08
10:29:04.000000000 +0100
+++ linux-2.6.21-rc3-ed/Documentation/filesystems/Locking 2007-03-08
12:08:56.000000000 +0100
@@ -15,6 +15,7 @@ prototypes:
int (*d_delete)(struct dentry *);
void (*d_release)(struct dentry *);
void (*d_iput)(struct dentry *, struct inode *);
+ char *(*d_dname)((struct dentry *dentry, char *buffer, int buflen);
locking rules:
none have BKL
@@ -25,6 +26,7 @@ d_compare: no yes no
no
d_delete: yes no yes no
d_release: no no no yes
d_iput: no no no yes
+d_dname: no no no no
--------------------------- inode_operations ---------------------------
prototypes:
--- linux-2.6.21-rc3/fs/dcache.c 2007-03-07 17:23:55.000000000 +0100
+++ linux-2.6.21-rc3-ed/fs/dcache.c 2007-03-08 17:47:04.000000000 +0100
@@ -1823,6 +1823,16 @@ char * d_path(struct dentry *dentry, str
struct vfsmount *rootmnt;
struct dentry *root;
+ /*
+ * We have various synthetic filesystems that never get mounted. On
+ * these filesystems dentries are never used for lookup purposes, and
+ * thus don't need to be hashed. They also don't need a name until a
+ * user wants to identify the object in /proc/pid/fd/. The little hack
+ * below allows us to generate a name for these objects on demand:
+ */
+ if (dentry->d_op && dentry->d_op->d_dname)
+ return dentry->d_op->d_dname(dentry, buf, buflen);
+
read_lock(¤t->fs->lock);
rootmnt = mntget(current->fs->rootmnt);
root = dget(current->fs->root);
--- linux-2.6.21-rc3/fs/pipe.c 2007-03-07 17:42:36.000000000 +0100
+++ linux-2.6.21-rc3-ed/fs/pipe.c 2007-03-08 17:44:06.000000000 +0100
@@ -841,8 +841,15 @@ static int pipefs_delete_dentry(struct d
return 0;
}
+static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
+{
+ snprintf(buffer, buflen, "pipe:[%lu]", dentry->d_inode->i_ino);
+ return buffer;
+}
+
static struct dentry_operations pipefs_dentry_operations = {
.d_delete = pipefs_delete_dentry,
+ .d_dname = pipefs_dname,
};
static struct inode * get_pipe_inode(void)
@@ -888,8 +895,7 @@ struct file *create_write_pipe(void)
struct inode *inode;
struct file *f;
struct dentry *dentry;
- char name[32];
- struct qstr this;
+ struct qstr name = { .name = "" };
f = get_empty_filp();
if (!f)
@@ -899,11 +905,8 @@ struct file *create_write_pipe(void)
if (!inode)
goto err_file;
- this.len = sprintf(name, "[%lu]", inode->i_ino);
- this.name = name;
- this.hash = 0;
err = -ENOMEM;
- dentry = d_alloc(pipe_mnt->mnt_sb->s_root, &this);
+ dentry = d_alloc(pipe_mnt->mnt_sb->s_root, &name);
if (!dentry)
goto err_inode;
--- linux-2.6.21-rc3/net/socket.c 2007-03-07 17:37:56.000000000 +0100
+++ linux-2.6.21-rc3-ed/net/socket.c 2007-03-08 11:57:41.000000000 +0100
@@ -314,8 +314,16 @@ static int sockfs_delete_dentry(struct d
dentry->d_flags |= DCACHE_UNHASHED;
return 0;
}
+
+static char *sockfs_dname(struct dentry *dentry, char *buffer, int buflen)
+{
+ snprintf(buffer, buflen, "socket:[%lu]", dentry->d_inode->i_ino);
+ return buffer;
+}
+
static struct dentry_operations sockfs_dentry_operations = {
.d_delete = sockfs_delete_dentry,
+ .d_dname = sockfs_dname,
};
/*
@@ -355,14 +363,9 @@ static int sock_alloc_fd(struct file **f
static int sock_attach_fd(struct socket *sock, struct file *file)
{
- struct qstr this;
- char name[32];
-
- this.len = sprintf(name, "[%lu]", SOCK_INODE(sock)->i_ino);
- this.name = name;
- this.hash = 0;
+ struct qstr name = { .name = "" };
- file->f_path.dentry = d_alloc(sock_mnt->mnt_sb->s_root, &this);
+ file->f_path.dentry = d_alloc(sock_mnt->mnt_sb->s_root, &name);
if (unlikely(!file->f_path.dentry))
return -ENOMEM;
