This is a note to let you know that I've just added the patch titled gfs2: Disable page faults during lockless buffered reads to the 5.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: gfs2-disable-page-faults-during-lockless-buffered-re.patch and it can be found in the queue-5.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 9f5dab140cd6e3e2161d208ecd250e76b971c767 Author: Andreas Gruenbacher <agruenba@xxxxxxxxxx> Date: Mon Mar 14 18:32:02 2022 +0100 gfs2: Disable page faults during lockless buffered reads [ Upstream commit 52f3f033a5dbd023307520af1ff551cadfd7f037 ] During lockless buffered reads, filemap_read() holds page cache page references while trying to copy data to the user-space buffer. The calling process isn't holding the inode glock, but the page references it holds prevent those pages from being removed from the page cache, and that prevents the underlying inode glock from being moved to another node. Thus, we can end up in the same kinds of distributed deadlock situations as with normal (non-lockless) buffered reads. Fix that by disabling page faults during lockless reads as well. Signed-off-by: Andreas Gruenbacher <agruenba@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c index eb5ea0262f3c..60390f9dc31f 100644 --- a/fs/gfs2/file.c +++ b/fs/gfs2/file.c @@ -963,14 +963,16 @@ static ssize_t gfs2_file_read_iter(struct kiocb *iocb, struct iov_iter *to) return ret; iocb->ki_flags &= ~IOCB_DIRECT; } + pagefault_disable(); iocb->ki_flags |= IOCB_NOIO; ret = generic_file_read_iter(iocb, to); iocb->ki_flags &= ~IOCB_NOIO; + pagefault_enable(); if (ret >= 0) { if (!iov_iter_count(to)) return ret; written = ret; - } else { + } else if (ret != -EFAULT) { if (ret != -EAGAIN) return ret; if (iocb->ki_flags & IOCB_NOWAIT)