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ANDROID: Revert "ANDROID: fs: pipe: wakeup readers on small writes even if pipe had data"

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This reverts commit
76879a1964 ("ANDROID: fs: pipe: wakeup readers on small writes even if pipe had data")
to replace that with the bug fix that landed upstream at
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3a34b13a88caeb2800ab44a4918f230041b37dd9

Bug: 193851993
Test: Build and boot cuttlefish.

Signed-off-by: Sandeep Patil <sspatil@android.com>
Change-Id: Ic4f5e2cc516b4ea68ae7d63225d1529217990431
This commit is contained in:
Sandeep Patil
2021-08-03 21:09:25 +00:00
parent dac8af7144
commit 6b7e007164
1 changed files with 9 additions and 10 deletions
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19
fs/pipe.c
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@@ -406,7 +406,7 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
ssize_t ret = 0;
size_t total_len = iov_iter_count(from);
ssize_t chars;
bool do_wakeup = false;
bool was_empty = false;
bool wake_next_writer = false;
/* Null write succeeds. */
@@ -429,11 +429,10 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
#endif
/*
* Wake up readers if the pipe was written to. Regardless
* of whether it was empty or not. Otherwise, threads
* waiting with EPOLLET will hang until the pipe is emptied.
* Only wake up if the pipe started out empty, since
* otherwise there should be no readers waiting.
*
* If pipe wasn't empty we try to merge new data into
* If it wasn't empty we try to merge new data into
* the last buffer.
*
* That naturally merges small writes, but it also
@@ -441,8 +440,9 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
* spanning multiple pages.
*/
head = pipe->head;
was_empty = pipe_empty(head, pipe->tail);
chars = total_len & (PAGE_SIZE-1);
if (chars && !pipe_empty(head, pipe->tail)) {
if (chars && !was_empty) {
unsigned int mask = pipe->ring_size - 1;
struct pipe_buffer *buf = &pipe->bufs[(head - 1) & mask];
int offset = buf->offset + buf->len;
@@ -460,7 +460,6 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
}
buf->len += ret;
do_wakeup = true;
if (!iov_iter_count(from))
goto out;
}
@@ -527,7 +526,6 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
ret += copied;
buf->offset = 0;
buf->len = copied;
do_wakeup = true;
if (!iov_iter_count(from))
break;
@@ -555,12 +553,13 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
* become empty while we dropped the lock.
*/
__pipe_unlock(pipe);
if (do_wakeup) {
if (was_empty) {
wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
}
wait_event_interruptible_exclusive(pipe->wr_wait, pipe_writable(pipe));
__pipe_lock(pipe);
was_empty = pipe_empty(pipe->head, pipe->tail);
wake_next_writer = true;
}
out:
@@ -577,7 +576,7 @@ out:
* how (for example) the GNU make jobserver uses small writes to
* wake up pending jobs
*/
if (do_wakeup) {
if (was_empty) {
wake_up_interruptible_sync_poll(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
}