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SubjectRe: [PATCH] fs: eventfd: fix obsolete comment
On Sat, Dec 07, 2019 at 03:45:33PM +0800, linmiaohe wrote:
> From: Miaohe Lin <linmiaohe@huawei.com>
>
> since commit 36a7411724b1 ("eventfd_ctx_fdget(): use fdget() instead of
> fget()"), this comment become outdated and looks confusing. Fix it with
> the correct function name.
>
> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
> ---
> fs/eventfd.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/eventfd.c b/fs/eventfd.c
> index 8aa0ea8c55e8..0b8466b12932 100644
> --- a/fs/eventfd.c
> +++ b/fs/eventfd.c
> @@ -352,7 +352,7 @@ EXPORT_SYMBOL_GPL(eventfd_fget);
> * Returns a pointer to the internal eventfd context, otherwise the error
> * pointers returned by the following functions:
> *
> - * eventfd_fget
> + * fdget

But this is wrong. The error pointer is returned from eventfd_ctx_fileget(),
not from fdget.

Looking at the three callers of eventfd_ctx_fileget(), I think it would
make sense to do this:

diff --git a/drivers/vfio/virqfd.c b/drivers/vfio/virqfd.c
index 997cb5d0a657..c35b614e3770 100644
--- a/drivers/vfio/virqfd.c
+++ b/drivers/vfio/virqfd.c
@@ -126,11 +126,6 @@ int vfio_virqfd_enable(void *opaque,
INIT_WORK(&virqfd->inject, virqfd_inject);

irqfd = fdget(fd);
- if (!irqfd.file) {
- ret = -EBADF;
- goto err_fd;
- }
-
ctx = eventfd_ctx_fileget(irqfd.file);
if (IS_ERR(ctx)) {
ret = PTR_ERR(ctx);
diff --git a/fs/eventfd.c b/fs/eventfd.c
index 8aa0ea8c55e8..d389ffd1dc07 100644
--- a/fs/eventfd.c
+++ b/fs/eventfd.c
@@ -349,17 +349,13 @@ EXPORT_SYMBOL_GPL(eventfd_fget);
* eventfd_ctx_fdget - Acquires a reference to the internal eventfd context.
* @fd: [in] Eventfd file descriptor.
*
- * Returns a pointer to the internal eventfd context, otherwise the error
- * pointers returned by the following functions:
- *
- * eventfd_fget
+ * Returns a pointer to the internal eventfd context, or an error pointer;
+ * see eventfd_ctx_fileget().
*/
struct eventfd_ctx *eventfd_ctx_fdget(int fd)
{
struct eventfd_ctx *ctx;
struct fd f = fdget(fd);
- if (!f.file)
- return ERR_PTR(-EBADF);
ctx = eventfd_ctx_fileget(f.file);
fdput(f);
return ctx;
@@ -368,17 +364,18 @@ EXPORT_SYMBOL_GPL(eventfd_ctx_fdget);

/**
* eventfd_ctx_fileget - Acquires a reference to the internal eventfd context.
- * @file: [in] Eventfd file pointer.
- *
- * Returns a pointer to the internal eventfd context, otherwise the error
- * pointer:
+ * @file: Eventfd file pointer.
*
- * -EINVAL : The @fd file descriptor is not an eventfd file.
+ * Return: A pointer to the internal eventfd context, or an error pointer:
+ * * -EBADF - The @file is NULL.
+ * * -EINVAL - The @file is not an eventfd file.
*/
struct eventfd_ctx *eventfd_ctx_fileget(struct file *file)
{
struct eventfd_ctx *ctx;

+ if (!file)
+ return ERR_PTR(-EBADF);
if (file->f_op != &eventfd_fops)
return ERR_PTR(-EINVAL);

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 01f3f8b665e9..74b45bc439d8 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4676,11 +4676,6 @@ static ssize_t memcg_write_event_control(struct kernfs_open_file *of,
INIT_WORK(&event->remove, memcg_event_remove);

efile = fdget(efd);
- if (!efile.file) {
- ret = -EBADF;
- goto out_kfree;
- }
-
event->eventfd = eventfd_ctx_fileget(efile.file);
if (IS_ERR(event->eventfd)) {
ret = PTR_ERR(event->eventfd);
diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
index 67b6fc153e9c..814b99c33d44 100644
--- a/virt/kvm/eventfd.c
+++ b/virt/kvm/eventfd.c
@@ -306,11 +306,6 @@ kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args)
seqcount_init(&irqfd->irq_entry_sc);

f = fdget(args->fd);
- if (!f.file) {
- ret = -EBADF;
- goto out;
- }
-
eventfd = eventfd_ctx_fileget(f.file);
if (IS_ERR(eventfd)) {
ret = PTR_ERR(eventfd);
(not even compile tested)

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