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authorJens Axboe <axboe@kernel.dk>2020-05-22 09:18:38 -0600
committerJens Axboe <axboe@kernel.dk>2020-05-23 08:26:07 -0600
commit12b9e99ac7b8d5e7956785b66c86b18f439c0308 (patch)
treeb5f63cd8e077a3e5c62918dc7e6d7b34dd46f6c9
parente097beda49b559dbdab0096f88a2bb23c37b935d (diff)
mm: support async buffered reads in generic_file_buffered_read()
Use the async page locking infrastructure, if IOCB_WAITQ is set in the passed in iocb. The caller must expect an -EIOCBQUEUED return value, which means that IO is started but not done yet. This is similar to how O_DIRECT signals the same operation. Once the callback is received by the caller for IO completion, the caller must retry the operation. Signed-off-by: Jens Axboe <axboe@kernel.dk>
-rw-r--r--mm/filemap.c33
1 files changed, 26 insertions, 7 deletions
diff --git a/mm/filemap.c b/mm/filemap.c
index c746541b1d49..a3b86c9acdc8 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1219,6 +1219,14 @@ static int __wait_on_page_locked_async(struct page *page,
return ret;
}
+static int wait_on_page_locked_async(struct page *page,
+ struct wait_page_queue *wait)
+{
+ if (!PageLocked(page))
+ return 0;
+ return __wait_on_page_locked_async(compound_head(page), wait, false);
+}
+
/**
* put_and_wait_on_page_locked - Drop a reference and wait for it to be unlocked
* @page: The page to wait for.
@@ -2058,17 +2066,25 @@ find_page:
index, last_index - index);
}
if (!PageUptodate(page)) {
- if (iocb->ki_flags & IOCB_NOWAIT) {
- put_page(page);
- goto would_block;
- }
-
/*
* See comment in do_read_cache_page on why
* wait_on_page_locked is used to avoid unnecessarily
* serialisations and why it's safe.
*/
- error = wait_on_page_locked_killable(page);
+ if (iocb->ki_flags & IOCB_WAITQ) {
+ if (written) {
+ put_page(page);
+ goto out;
+ }
+ error = wait_on_page_locked_async(page,
+ iocb->private);
+ } else {
+ if (iocb->ki_flags & IOCB_NOWAIT) {
+ put_page(page);
+ goto would_block;
+ }
+ error = wait_on_page_locked_killable(page);
+ }
if (unlikely(error))
goto readpage_error;
if (PageUptodate(page))
@@ -2156,7 +2172,10 @@ page_ok:
page_not_up_to_date:
/* Get exclusive access to the page ... */
- error = lock_page_killable(page);
+ if (iocb->ki_flags & IOCB_WAITQ)
+ error = lock_page_async(page, iocb->private);
+ else
+ error = lock_page_killable(page);
if (unlikely(error))
goto readpage_error;