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Message-ID: <alpine.DEB.1.10.0905031252540.7899@makko.or.mcafeemobile.com>
Date: Sun, 3 May 2009 13:11:39 -0700 (PDT)
From: Davide Libenzi <davidel@...ilserver.org>
To: Al Viro <viro@...IV.linux.org.uk>
cc: Gregory Haskins <ghaskins@...ell.com>, kvm@...r.kernel.org,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
avi@...hat.com
Subject: Re: [KVM PATCH v3 2/2] kvm: add support for irqfd via eventfd-notification
interface
On Sun, 3 May 2009, Al Viro wrote:
> IOW, the sane solution would be to export something that returns your
> struct file *. And stop playing with fd completely.
This builds but it's not tested at all.
- Make all the work of the old anon_inode_getfd(), done by a new
anon_inode_getfile(), with anon_inode_getfd() using its services
- Make all the work done by sys_eventfd(), done by a new
eventfd_file_create() (which in turn uses anon_inode_getfile()), with
sys_eventfd() using its services
IRQfd can use eventfd_file_create(), fget(), get_unused_fd_flags() and
fd_install() just before returning.
Is that what you had in mind?
- Davide
---
fs/anon_inodes.c | 68 +++++++++++++++++++++++++++++++++-----------
fs/eventfd.c | 44 +++++++++++++++++++++-------
include/linux/anon_inodes.h | 3 +
include/linux/eventfd.h | 6 +++
4 files changed, 92 insertions(+), 29 deletions(-)
Index: linux-2.6.mod/fs/anon_inodes.c
===================================================================
--- linux-2.6.mod.orig/fs/anon_inodes.c 2009-05-03 12:21:09.000000000 -0700
+++ linux-2.6.mod/fs/anon_inodes.c 2009-05-03 12:54:02.000000000 -0700
@@ -64,28 +64,24 @@ static const struct dentry_operations an
*
* Creates a new file by hooking it on a single inode. This is useful for files
* that do not need to have a full-fledged inode in order to operate correctly.
- * All the files created with anon_inode_getfd() will share a single inode,
+ * All the files created with anon_inode_getfile() will share a single inode,
* hence saving memory and avoiding code duplication for the file/inode/dentry
- * setup. Returns new descriptor or -error.
+ * setup. Returns the newly created file* or error.
*/
-int anon_inode_getfd(const char *name, const struct file_operations *fops,
- void *priv, int flags)
+struct file *anon_inode_getfile(const char *name,
+ const struct file_operations *fops,
+ void *priv, int flags)
{
struct qstr this;
struct dentry *dentry;
struct file *file;
- int error, fd;
+ int error;
if (IS_ERR(anon_inode_inode))
- return -ENODEV;
+ return ERR_PTR(-ENODEV);
if (fops->owner && !try_module_get(fops->owner))
- return -ENOENT;
-
- error = get_unused_fd_flags(flags);
- if (error < 0)
- goto err_module;
- fd = error;
+ return ERR_PTR(-ENOENT);
/*
* Link the inode to a directory entry by creating a unique name
@@ -97,7 +93,7 @@ int anon_inode_getfd(const char *name, c
this.hash = 0;
dentry = d_alloc(anon_inode_mnt->mnt_sb->s_root, &this);
if (!dentry)
- goto err_put_unused_fd;
+ goto err_module;
/*
* We know the anon_inode inode count is always greater than zero,
@@ -123,16 +119,54 @@ int anon_inode_getfd(const char *name, c
file->f_version = 0;
file->private_data = priv;
+ return file;
+
+err_dput:
+ dput(dentry);
+err_module:
+ module_put(fops->owner);
+ return ERR_PTR(error);
+}
+EXPORT_SYMBOL_GPL(anon_inode_getfile);
+
+/**
+ * anon_inode_getfd - creates a new file instance by hooking it up to an
+ * anonymous inode, and a dentry that describe the "class"
+ * of the file
+ *
+ * @name: [in] name of the "class" of the new file
+ * @fops: [in] file operations for the new file
+ * @priv: [in] private data for the new file (will be file's private_data)
+ * @flags: [in] flags
+ *
+ * Creates a new file by hooking it on a single inode. This is useful for files
+ * that do not need to have a full-fledged inode in order to operate correctly.
+ * All the files created with anon_inode_getfd() will share a single inode,
+ * hence saving memory and avoiding code duplication for the file/inode/dentry
+ * setup. Returns new descriptor or -error.
+ */
+int anon_inode_getfd(const char *name, const struct file_operations *fops,
+ void *priv, int flags)
+{
+ int error, fd;
+ struct file *file;
+
+ error = get_unused_fd_flags(flags);
+ if (error < 0)
+ return error;
+ fd = error;
+
+ file = anon_inode_getfile(name, fops, priv, flags);
+ if (IS_ERR(file)) {
+ error = PTR_ERR(file);
+ goto err_put_unused_fd;
+ }
fd_install(fd, file);
return fd;
-err_dput:
- dput(dentry);
err_put_unused_fd:
put_unused_fd(fd);
-err_module:
- module_put(fops->owner);
return error;
}
EXPORT_SYMBOL_GPL(anon_inode_getfd);
Index: linux-2.6.mod/fs/eventfd.c
===================================================================
--- linux-2.6.mod.orig/fs/eventfd.c 2009-05-03 12:21:09.000000000 -0700
+++ linux-2.6.mod/fs/eventfd.c 2009-05-03 12:54:07.000000000 -0700
@@ -198,9 +198,9 @@ struct file *eventfd_fget(int fd)
return file;
}
-SYSCALL_DEFINE2(eventfd2, unsigned int, count, int, flags)
+struct file *eventfd_file_create(unsigned int count, int flags)
{
- int fd;
+ struct file *file;
struct eventfd_ctx *ctx;
/* Check the EFD_* constants for consistency. */
@@ -208,25 +208,47 @@ SYSCALL_DEFINE2(eventfd2, unsigned int,
BUILD_BUG_ON(EFD_NONBLOCK != O_NONBLOCK);
if (flags & ~EFD_FLAGS_SET)
- return -EINVAL;
+ return ERR_PTR(-EINVAL);
ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
if (!ctx)
- return -ENOMEM;
+ return ERR_PTR(-ENOMEM);
init_waitqueue_head(&ctx->wqh);
ctx->count = count;
ctx->flags = flags;
- /*
- * When we call this, the initialization must be complete, since
- * anon_inode_getfd() will install the fd.
- */
- fd = anon_inode_getfd("[eventfd]", &eventfd_fops, ctx,
- flags & EFD_SHARED_FCNTL_FLAGS);
- if (fd < 0)
+ file = anon_inode_getfile("[eventfd]", &eventfd_fops, ctx,
+ flags & EFD_SHARED_FCNTL_FLAGS);
+ if (IS_ERR(file))
kfree(ctx);
+
+ return file;
+}
+
+SYSCALL_DEFINE2(eventfd2, unsigned int, count, int, flags)
+{
+ int fd, error;
+ struct file *file;
+
+ error = get_unused_fd_flags(flags & EFD_SHARED_FCNTL_FLAGS);
+ if (error < 0)
+ return error;
+ fd = error;
+
+ file = eventfd_file_create(count, flags);
+ if (IS_ERR(file)) {
+ error = PTR_ERR(file);
+ goto err_put_unused_fd;
+ }
+ fd_install(fd, file);
+
return fd;
+
+err_put_unused_fd:
+ put_unused_fd(fd);
+
+ return error;
}
SYSCALL_DEFINE1(eventfd, unsigned int, count)
Index: linux-2.6.mod/include/linux/anon_inodes.h
===================================================================
--- linux-2.6.mod.orig/include/linux/anon_inodes.h 2009-05-03 12:21:09.000000000 -0700
+++ linux-2.6.mod/include/linux/anon_inodes.h 2009-05-03 12:48:08.000000000 -0700
@@ -8,6 +8,9 @@
#ifndef _LINUX_ANON_INODES_H
#define _LINUX_ANON_INODES_H
+struct file *anon_inode_getfile(const char *name,
+ const struct file_operations *fops,
+ void *priv, int flags);
int anon_inode_getfd(const char *name, const struct file_operations *fops,
void *priv, int flags);
Index: linux-2.6.mod/include/linux/eventfd.h
===================================================================
--- linux-2.6.mod.orig/include/linux/eventfd.h 2009-05-03 12:21:09.000000000 -0700
+++ linux-2.6.mod/include/linux/eventfd.h 2009-05-03 12:43:54.000000000 -0700
@@ -29,12 +29,16 @@
struct file *eventfd_fget(int fd);
int eventfd_signal(struct file *file, int n);
+struct file *eventfd_file_create(unsigned int count, int flags);
#else /* CONFIG_EVENTFD */
-#define eventfd_fget(fd) ERR_PTR(-ENOSYS)
+static inline struct file *eventfd_fget(int fd)
+{ ERR_PTR(-ENOSYS); }
static inline int eventfd_signal(struct file *file, int n)
{ return 0; }
+struct file *eventfd_file_create(unsigned int count, int flags)
+{ ERR_PTR(-ENOSYS); }
#endif /* CONFIG_EVENTFD */
--
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