Merge tag 'for-5.20/io_uring-buffered-writes-2022-07-29' of git://git.kernel.dk/linux-block

Pull io_uring buffered writes support from Jens Axboe:
 "This contains support for buffered writes, specifically for XFS. btrfs
  is in progress, will be coming in the next release.

  io_uring does support buffered writes on any file type, but since the
  buffered write path just always -EAGAIN (or -EOPNOTSUPP) any attempt
  to do so if IOCB_NOWAIT is set, any buffered write will effectively be
  handled by io-wq offload. This isn't very efficient, and we even have
  specific code in io-wq to serialize buffered writes to the same inode
  to avoid further inefficiencies with thread offload.

  This is particularly sad since most buffered writes don't block, they
  simply copy data to a page and dirty it. With this pull request, we
  can handle buffered writes a lot more effiently.

  If balance_dirty_pages() needs to block, we back off on writes as
  indicated.

  This improves buffered write support by 2-3x.

  Jan Kara helped with the mm bits for this, and Stefan handled the
  fs/iomap/xfs/io_uring parts of it"

* tag 'for-5.20/io_uring-buffered-writes-2022-07-29' of git://git.kernel.dk/linux-block:
  mm: honor FGP_NOWAIT for page cache page allocation
  xfs: Add async buffered write support
  xfs: Specify lockmode when calling xfs_ilock_for_iomap()
  io_uring: Add tracepoint for short writes
  io_uring: fix issue with io_write() not always undoing sb_start_write()
  io_uring: Add support for async buffered writes
  fs: Add async write file modification handling.
  fs: Split off inode_needs_update_time and __file_update_time
  fs: add __remove_file_privs() with flags parameter
  fs: add a FMODE_BUF_WASYNC flags for f_mode
  iomap: Return -EAGAIN from iomap_write_iter()
  iomap: Add async buffered write support
  iomap: Add flags parameter to iomap_page_create()
  mm: Add balance_dirty_pages_ratelimited_flags() function
  mm: Move updates of dirty_exceeded into one place
  mm: Move starting of background writeback into the main balancing loop

1 files changed, 25 insertions, 0 deletions

diff --git a/include/trace/events/io_uring.h b/include/trace/events/io_uring.h
index 95a8cfaad15a..c5b21ff0ac85 100644
--- a/include/trace/events/io_uring.h
+++ b/include/trace/events/io_uring.h
@@ -630,6 +630,31 @@ TRACE_EVENT(io_uring_task_work_run,
 		 __entry->tctx, __entry->count, __entry->loops)
 );
 
+TRACE_EVENT(io_uring_short_write,
+
+	TP_PROTO(void *ctx, u64 fpos, u64 wanted, u64 got),
+
+	TP_ARGS(ctx, fpos, wanted, got),
+
+	TP_STRUCT__entry(
+		__field(void *,	ctx)
+		__field(u64,	fpos)
+		__field(u64,	wanted)
+		__field(u64,	got)
+	),
+
+	TP_fast_assign(
+		__entry->ctx	= ctx;
+		__entry->fpos	= fpos;
+		__entry->wanted	= wanted;
+		__entry->got	= got;
+	),
+
+	TP_printk("ring %p, fpos %lld, wanted %lld, got %lld",
+			  __entry->ctx, __entry->fpos,
+			  __entry->wanted, __entry->got)
+);
+
 #endif /* _TRACE_IO_URING_H */
 
 /* This part must be outside protection */