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Merge branch 'work.epoll' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

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Pull epoll updates from Al Viro:
 "Deal with epoll loop check/removal races sanely (among other things).

  The solution merged last cycle (pinning a bunch of struct file
  instances) had been forced by the wrong data structures; untangling
  that takes a bunch of preparations, but it's worth doing - control
  flow in there is ridiculously overcomplicated. Memory footprint has
  also gone down, while we are at it.

  This is not all I want to do in the area, but since I didn't get
  around to posting the followups they'll have to wait for the next
  cycle"

* 'work.epoll' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (27 commits)
  epoll: take epitem list out of struct file
  epoll: massage the check list insertion
  lift rcu_read_lock() into reverse_path_check()
  convert ->f_ep_links/->fllink to hlist
  ep_insert(): move creation of wakeup source past the fl_ep_links insertion
  fold ep_read_events_proc() into the only caller
  take the common part of ep_eventpoll_poll() and ep_item_poll() into helper
  ep_insert(): we only need tep->mtx around the insertion itself
  ep_insert(): don't open-code ep_remove() on failure exits
  lift locking/unlocking ep->mtx out of ep_{start,done}_scan()
  ep_send_events_proc(): fold into the caller
  lift the calls of ep_send_events_proc() into the callers
  lift the calls of ep_read_events_proc() into the callers
  ep_scan_ready_list(): prepare to splitup
  ep_loop_check_proc(): saner calling conventions
  get rid of ep_push_nested()
  ep_loop_check_proc(): lift pushing the cookie into callers
  clean reverse_path_check_proc() a bit
  reverse_path_check_proc(): don't bother with cookies
  reverse_path_check_proc(): sane arguments
  ...
This commit is contained in:
Linus Torvalds 2020-12-15 19:01:08 -08:00
commit 1a825a6a0e
4 changed files with 305 additions and 429 deletions
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717
fs/eventpoll.c
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File diff suppressed because it is too large Load Diff

1
fs/file_table.c
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@ -113,7 +113,6 @@ static struct file *__alloc_file(int flags, const struct cred *cred)
rwlock_init(&f->f_owner.lock);
spin_lock_init(&f->f_lock);
mutex_init(&f->f_pos_lock);
eventpoll_init_file(f);
f->f_flags = flags;
f->f_mode = OPEN_FMODE(flags);
/* f->f_version: 0 */

11
include/linux/eventpoll.h
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@ -22,14 +22,6 @@ struct file;
struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd, unsigned long toff);
#endif
/* Used to initialize the epoll bits inside the "struct file" */
static inline void eventpoll_init_file(struct file *file)
{
INIT_LIST_HEAD(&file->f_ep_links);
INIT_LIST_HEAD(&file->f_tfile_llink);
}
/* Used to release the epoll bits inside the "struct file" */
void eventpoll_release_file(struct file *file);
@ -50,7 +42,7 @@ static inline void eventpoll_release(struct file *file)
* because the file in on the way to be removed and nobody ( but
* eventpoll ) has still a reference to this file.
*/
if (likely(list_empty(&file->f_ep_links)))
if (likely(!file->f_ep))
return;
/*
@ -72,7 +64,6 @@ static inline int ep_op_has_event(int op)
#else
static inline void eventpoll_init_file(struct file *file) {}
static inline void eventpoll_release(struct file *file) {}
#endif

5
include/linux/fs.h
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@ -923,7 +923,7 @@ struct file {
const struct file_operations *f_op;
/*
* Protects f_ep_links, f_flags.
* Protects f_ep, f_flags.
* Must not be taken from IRQ context.
*/
spinlock_t f_lock;
@ -946,8 +946,7 @@ struct file {
#ifdef CONFIG_EPOLL
/* Used by fs/eventpoll.c to link all the hooks to this file */
struct list_head f_ep_links;
struct list_head f_tfile_llink;
struct hlist_head *f_ep;
#endif /* #ifdef CONFIG_EPOLL */
struct address_space *f_mapping;
errseq_t f_wb_err;