linux-kernel - [PATCH 1/3] eventfd: convert to use anon_inode

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Date:   Sat,  6 Jan 2018 09:45:42 -0800
From:   Eric Biggers <ebiggers3@...il.com>
To:     linux-fsdevel@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Davide Libenzi <davidel@...ilserver.org>,
        Eric Biggers <ebiggers@...gle.com>
Subject: [PATCH 1/3] eventfd: convert to use anon_inode_getfd()

From: Eric Biggers <ebiggers@...gle.com>

Nothing actually calls eventfd_file_create() besides the eventfd2()
system call itself.  So simplify things by folding it into the system
call and using anon_inode_getfd() instead of anon_inode_getfile().  This
removes over 40 lines with no change in functionality.

(eventfd_file_create() was apparently added years ago for KVM irqfd's,
but was never used.)

Signed-off-by: Eric Biggers <ebiggers@...gle.com>
---
 fs/eventfd.c            | 53 +++++++------------------------------------------
 include/linux/eventfd.h |  5 -----
 2 files changed, 7 insertions(+), 51 deletions(-)

diff --git a/fs/eventfd.c b/fs/eventfd.c
index 2fb4eadaa118..4167e670ed4d 100644
--- a/fs/eventfd.c
+++ b/fs/eventfd.c
@@ -412,72 +412,33 @@ struct eventfd_ctx *eventfd_ctx_fileget(struct file *file)
 }
 EXPORT_SYMBOL_GPL(eventfd_ctx_fileget);
 
-/**
- * eventfd_file_create - Creates an eventfd file pointer.
- * @count: Initial eventfd counter value.
- * @flags: Flags for the eventfd file.
- *
- * This function creates an eventfd file pointer, w/out installing it into
- * the fd table. This is useful when the eventfd file is used during the
- * initialization of data structures that require extra setup after the eventfd
- * creation. So the eventfd creation is split into the file pointer creation
- * phase, and the file descriptor installation phase.
- * In this way races with userspace closing the newly installed file descriptor
- * can be avoided.
- * Returns an eventfd file pointer, or a proper error pointer.
- */
-struct file *eventfd_file_create(unsigned int count, int flags)
+SYSCALL_DEFINE2(eventfd2, unsigned int, count, int, flags)
 {
-	struct file *file;
 	struct eventfd_ctx *ctx;
+	int fd;
 
 	/* Check the EFD_* constants for consistency.  */
 	BUILD_BUG_ON(EFD_CLOEXEC != O_CLOEXEC);
 	BUILD_BUG_ON(EFD_NONBLOCK != O_NONBLOCK);
 
 	if (flags & ~EFD_FLAGS_SET)
-		return ERR_PTR(-EINVAL);
+		return -EINVAL;
 
 	ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
 	if (!ctx)
-		return ERR_PTR(-ENOMEM);
+		return -ENOMEM;
 
 	kref_init(&ctx->kref);
 	init_waitqueue_head(&ctx->wqh);
 	ctx->count = count;
 	ctx->flags = flags;
 
-	file = anon_inode_getfile("[eventfd]", &eventfd_fops, ctx,
-				  O_RDWR | (flags & EFD_SHARED_FCNTL_FLAGS));
-	if (IS_ERR(file))
+	fd = anon_inode_getfd("[eventfd]", &eventfd_fops, ctx,
+			      O_RDWR | (flags & EFD_SHARED_FCNTL_FLAGS));
+	if (fd < 0)
 		eventfd_free_ctx(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)
diff --git a/include/linux/eventfd.h b/include/linux/eventfd.h
index 60b2985e8a18..15826192cc23 100644
--- a/include/linux/eventfd.h
+++ b/include/linux/eventfd.h
@@ -30,7 +30,6 @@ struct file;
 
 #ifdef CONFIG_EVENTFD
 
-struct file *eventfd_file_create(unsigned int count, int flags);
 struct eventfd_ctx *eventfd_ctx_get(struct eventfd_ctx *ctx);
 void eventfd_ctx_put(struct eventfd_ctx *ctx);
 struct file *eventfd_fget(int fd);
@@ -47,10 +46,6 @@ int eventfd_ctx_remove_wait_queue(struct eventfd_ctx *ctx, wait_queue_entry_t *w
  * Ugly ugly ugly error layer to support modules that uses eventfd but
  * pretend to work in !CONFIG_EVENTFD configurations. Namely, AIO.
  */
-static inline struct file *eventfd_file_create(unsigned int count, int flags)
-{
-	return ERR_PTR(-ENOSYS);
-}
 
 static inline struct eventfd_ctx *eventfd_ctx_fdget(int fd)
 {
-- 
2.15.1