From: "Michael S. Tsirkin" <mst@mellanox.co.il>
To: discuss@x86-64.org
Cc: linux-kernel@vger.kernel.org
Subject: f_ops flag to speed up compatible ioctls in linux kernel
Date: Wed, 1 Sep 2004 10:22:45 +0300 [thread overview]
Message-ID: <20040901072245.GF13749@mellanox.co.il> (raw)
Hello!
Currently, on the x86_64 architecture, its quite tricky to make
a char device ioctl work for an x86 executables.
In particular,
1. there is a requirement that ioctl number is unique -
which is hard to guarantee especially for out of kernel modules
2. there's a performance huge overhead for each compat call - there's
a hash lookup in a global hash inside a lock_kernel -
and I think compat performance *is* important.
Further, adding a command to the ioctl suddenly requires changing
two places - registration code and ioctl itself.
However, if all ioctl commands for a specific device
are not passing around pointers and long longs,
(relatively common case), and sometimes even
if they are, this ioctl is 64/32 bit compatible -
so why isnt there a simple way to declare this fact?
Here's a patch that simply adds a flag field to f_ops
that will cause all ioctls to get forwarded directly to the
64 bit call.
If all ioctls are compatible for a character device, a flag just
has to be set there, before the device is registered.
MST
diff -ruw linux-2.6.8.1/fs/compat.c linux-2.6.8.1-built/fs/compat.c
--- linux-2.6.8.1/fs/compat.c 2004-08-14 13:55:31.000000000 +0300
+++ linux-2.6.8.1-built/fs/compat.c 2004-09-01 09:52:10.126944256 +0300
@@ -392,7 +392,8 @@
if(!filp)
goto out2;
- if (!filp->f_op || !filp->f_op->ioctl) {
+ if (!filp->f_op || !filp->f_op->ioctl ||
+ (filp->f_op->fops_flags & FOPS_IOCTL_COMPAT)) {
error = sys_ioctl (fd, cmd, arg);
goto out;
}
diff -ruw linux-2.6.8.1/include/linux/fs.h linux-2.6.8.1-built/include/linux/fs.h
--- linux-2.6.8.1/include/linux/fs.h 2004-08-14 13:55:09.000000000 +0300
+++ linux-2.6.8.1-built/include/linux/fs.h 2004-09-01 09:50:07.265622016 +0300
@@ -871,6 +871,7 @@
*/
struct file_operations {
struct module *owner;
+ unsigned long fops_flags; /* Flags, listed below. */
loff_t (*llseek) (struct file *, loff_t, int);
ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
ssize_t (*aio_read) (struct kiocb *, char __user *, size_t, loff_t);
@@ -896,6 +897,8 @@
int (*dir_notify)(struct file *filp, unsigned long arg);
};
+#define FOPS_IOCTL_COMPAT 0x00000001 /* ioctl is 32/64 bit compatible */
+
struct inode_operations {
int (*create) (struct inode *,struct dentry *,int, struct nameidata *);
struct dentry * (*lookup) (struct inode *,struct dentry *, struct nameidata *);
next reply other threads:[~2004-09-01 7:20 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-09-01 7:22 Michael S. Tsirkin [this message]
2004-09-01 7:32 ` f_ops flag to speed up compatible ioctls in linux kernel viro
2004-09-01 7:44 ` Michael S. Tsirkin
2004-09-01 7:47 ` Lee Revell
2004-09-01 8:19 ` Michael S. Tsirkin
2004-09-01 15:55 ` Roland Dreier
2004-09-01 18:02 ` Chris Wright
2004-09-01 18:12 ` Roland Dreier
2004-09-01 18:31 ` viro
2004-09-01 20:54 ` Roland Dreier
[not found] ` <20040901170800.K1924@build.pdx.osdl.net>
[not found] ` <20040901190122.L1924@build.pdx.osdl.net>
2004-09-02 3:46 ` Roland Dreier
2004-09-01 18:06 ` Bill Davidsen
2004-09-01 8:30 ` Arjan van de Ven
2004-09-01 15:40 ` [PATCH] fs/compat.c: rwsem instead of BKL around ioctl32_hash_table Roland Dreier
2004-09-01 23:27 ` Andrew Morton
2004-09-02 21:14 ` Andi Kleen
2004-09-02 22:26 ` Roland Dreier
2004-09-03 14:37 ` [discuss] " Andi Kleen
2004-09-03 14:55 ` Roland Dreier
2004-09-03 15:02 ` Andi Kleen
2004-09-03 8:00 ` [discuss] f_ops flag to speed up compatible ioctls in linux kernel Andi Kleen
2004-09-07 10:40 ` Michael S. Tsirkin
2004-09-07 12:14 ` Andi Kleen
2004-09-07 13:45 ` Michael S. Tsirkin
2004-09-07 14:15 ` Andi Kleen
2004-09-07 14:25 ` Michael S. Tsirkin
2004-09-07 14:29 ` Andi Kleen
2004-09-07 14:37 ` Michael S. Tsirkin
2004-09-07 14:44 ` Andi Kleen
2004-09-07 14:45 ` Michael S. Tsirkin
2004-09-07 15:10 ` Andi Kleen
2004-09-07 18:16 ` Michael S. Tsirkin
2004-09-08 6:55 ` Andi Kleen
2004-09-08 14:28 ` [patch] " Michael S. Tsirkin
2004-09-08 14:38 ` Andi Kleen
2004-09-08 14:54 ` Michael S. Tsirkin
2004-09-08 14:58 ` Andi Kleen
2004-09-12 20:05 ` Michael S. Tsirkin
2004-09-15 13:19 ` [patch] Re: [discuss] " Michael S. Tsirkin
2004-09-07 21:36 ` Is FIOQSIZE compatible? ( was Re: f_ops flag to speed up compatible ioctls in linux kernel) Michael S. Tsirkin
2004-09-08 6:54 ` Andi Kleen
2004-09-07 15:03 ` [discuss] f_ops flag to speed up compatible ioctls in linux kernel Herbert Poetzl
2004-09-07 18:07 ` Michael S. Tsirkin
2004-09-09 13:54 ` Herbert Poetzl
2004-12-12 21:51 ` how to detect a 32 bit process on 64 bit kernel Michael S. Tsirkin
2004-12-12 22:01 ` Jan Engelhardt
2004-12-12 22:23 ` Christoph Hellwig
2004-12-13 19:50 ` Michael S. Tsirkin
2004-12-13 21:01 ` Jan Engelhardt
2004-12-13 21:32 ` Brian Gerst
2004-12-13 21:37 ` Michael S. Tsirkin
2004-12-12 22:37 ` Willy Tarreau
2004-12-12 23:30 ` Bongani Hlope
2004-12-14 7:28 ` Andi Kleen
2004-09-20 14:49 ` [patch] speed up ioctls in linux kernel Michael S. Tsirkin
2004-09-01 9:50 f_ops flag to speed up compatible " filia
2004-09-01 9:52 ` Arjan van de Ven
2004-09-01 10:16 ` filia
[not found] ` <4135B9FC.7050602@hist.no>
2004-09-01 13:29 ` Ihar 'Philips' Filipau
2004-09-01 15:28 ` Ihar 'Philips' Filipau
2004-09-02 7:29 ` Helge Hafting
2004-09-01 13:43 ` Olivier Galibert
2004-09-01 15:36 Albert Cahalan
2004-09-01 15:59 ` Roland Dreier
2004-09-01 21:53 ` Michael S. Tsirkin
2004-09-01 22:58 ` Roland Dreier
2004-09-01 23:18 ` Michael S. Tsirkin
2004-09-01 15:40 Albert Cahalan
2004-09-01 21:23 ` Michael S. Tsirkin
2004-09-01 21:38 ` Lee Revell
2004-09-01 21:43 ` Chris Wright
2004-09-01 21:44 ` Roland Dreier
2004-12-27 22:22 Michael S. Tsirkin
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