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authorLinus Torvalds <torvalds@linux-foundation.org>2018-06-28 09:43:44 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-06-28 10:40:47 -0700
commita11e1d432b51f63ba698d044441284a661f01144 (patch)
tree9f3c5a10bf0d7f9a342d5fb39c0c35ea14170124 /fs/select.c
parentf57494321cbf5b1e7769b6135407d2995a369e28 (diff)
downloadlinux-a11e1d432b51f63ba698d044441284a661f01144.tar.bz2
Revert changes to convert to ->poll_mask() and aio IOCB_CMD_POLL
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>
Diffstat (limited to 'fs/select.c')
-rw-r--r--fs/select.c23
1 files changed, 0 insertions, 23 deletions
diff --git a/fs/select.c b/fs/select.c
index 317891ff8165..4a6b6e4b21cb 100644
--- a/fs/select.c
+++ b/fs/select.c
@@ -34,29 +34,6 @@
#include <linux/uaccess.h>
-__poll_t vfs_poll(struct file *file, struct poll_table_struct *pt)
-{
- if (file->f_op->poll) {
- return file->f_op->poll(file, pt);
- } else if (file_has_poll_mask(file)) {
- unsigned int events = poll_requested_events(pt);
- struct wait_queue_head *head;
-
- if (pt && pt->_qproc) {
- head = file->f_op->get_poll_head(file, events);
- if (!head)
- return DEFAULT_POLLMASK;
- if (IS_ERR(head))
- return EPOLLERR;
- pt->_qproc(file, head, pt);
- }
-
- return file->f_op->poll_mask(file, events);
- } else {
- return DEFAULT_POLLMASK;
- }
-}
-EXPORT_SYMBOL_GPL(vfs_poll);
/*
* Estimate expected accuracy in ns from a timeval.