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Revert changes to convert to ->poll_mask() and aio IOCB_CMD_POLL

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The poll() changes were not well thought out, and completely
unexplained.  They also caused a huge performance regression, because
"->poll()" was no longer a trivial file operation that just called down
to the underlying file operations, but instead did at least two indirect
calls.

Indirect calls are sadly slow now with the Spectre mitigation, but the
performance problem could at least be largely mitigated by changing the
"->get_poll_head()" operation to just have a per-file-descriptor pointer
to the poll head instead.  That gets rid of one of the new indirections.

But that doesn't fix the new complexity that is completely unwarranted
for the regular case.  The (undocumented) reason for the poll() changes
was some alleged AIO poll race fixing, but we don't make the common case
slower and more complex for some uncommon special case, so this all
really needs way more explanations and most likely a fundamental
redesign.

[ This revert is a revert of about 30 different commits, not reverted
  individually because that would just be unnecessarily messy  - Linus ]

Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Linus Torvalds
2018-06-28 09:43:44 -07:00
parent f57494321c
commit a11e1d432b
80 changed files with 302 additions and 451 deletions
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2
include/linux/fs.h
View File

@@ -1720,8 +1720,6 @@ struct file_operations {
int (*iterate) (struct file *, struct dir_context *);
int (*iterate_shared) (struct file *, struct dir_context *);
__poll_t (*poll) (struct file *, struct poll_table_struct *);
struct wait_queue_head * (*get_poll_head)(struct file *, __poll_t);
__poll_t (*poll_mask) (struct file *, __poll_t);
long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
int (*mmap) (struct file *, struct vm_area_struct *);

1
include/linux/net.h
View File

@@ -147,7 +147,6 @@ struct proto_ops {
int (*getname) (struct socket *sock,
struct sockaddr *addr,
int peer);
__poll_t (*poll_mask) (struct socket *sock, __poll_t events);
__poll_t (*poll) (struct file *file, struct socket *sock,
struct poll_table_struct *wait);
int (*ioctl) (struct socket *sock, unsigned int cmd,

14
include/linux/poll.h
View File

@@ -74,17 +74,17 @@ static inline void init_poll_funcptr(poll_table *pt, poll_queue_proc qproc)
pt->_key = ~(__poll_t)0; /* all events enabled */
}
static inline bool file_has_poll_mask(struct file *file)
{
return file->f_op->get_poll_head && file->f_op->poll_mask;
}
static inline bool file_can_poll(struct file *file)
{
return file->f_op->poll || file_has_poll_mask(file);
return file->f_op->poll;
}
__poll_t vfs_poll(struct file *file, struct poll_table_struct *pt);
static inline __poll_t vfs_poll(struct file *file, struct poll_table_struct *pt)
{
if (unlikely(!file->f_op->poll))
return DEFAULT_POLLMASK;
return file->f_op->poll(file, pt);
}
struct poll_table_entry {
struct file *filp;

3
include/linux/skbuff.h
View File

@@ -3252,7 +3252,8 @@ struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned flags,
int *peeked, int *off, int *err);
struct sk_buff *skb_recv_datagram(struct sock *sk, unsigned flags, int noblock,
int *err);
__poll_t datagram_poll_mask(struct socket *sock, __poll_t events);
__poll_t datagram_poll(struct file *file, struct socket *sock,
struct poll_table_struct *wait);
int skb_copy_datagram_iter(const struct sk_buff *from, int offset,
struct iov_iter *to, int size);
static inline int skb_copy_datagram_msg(const struct sk_buff *from, int offset,