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) Adds a dynamic_dname() helper function that eases d_dname() implementations
3) Defines d_dname method for sockets : No more sprintf() at socket
creation. This is delayed up to the moment someone does an access to
/proc/pid/fd/...
4) Defines d_dname 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 <dada1@cosmosbay.com>
Acked-by: Christoph Hellwig <hch@infradead.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/pipe.c b/fs/pipe.c
index ebafde7..3a89592 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -841,8 +841,18 @@
return 0;
}
+/*
+ * pipefs_dname() is called from d_path().
+ */
+static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
+{
+ return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
+ dentry->d_inode->i_ino);
+}
+
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 +898,7 @@
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 +908,8 @@
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;