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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Andreas Gruenbacher <agruenba@redhat.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.15 122/177] gfs2: No short reads or writes upon glock contention
Date:   Wed,  4 May 2022 18:45:15 +0200
Message-Id: <20220504153104.053123041@linuxfoundation.org>
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From: Andreas Gruenbacher <agruenba@redhat.com>

[ Upstream commit 296abc0d91d8b65d42224dd33452ace14491ad08 ]

Commit 00bfe02f4796 ("gfs2: Fix mmap + page fault deadlocks for buffered
I/O") changed gfs2_file_read_iter() and gfs2_file_buffered_write() to
allow dropping the inode glock while faulting in user buffers.  When the
lock was dropped, a short result was returned to indicate that the
operation was interrupted.

As pointed out by Linus (see the link below), this behavior is broken
and the operations should always re-acquire the inode glock and resume
the operation instead.

Link: https://lore.kernel.org/lkml/CAHk-=whaz-g_nOOoo8RRiWNjnv2R+h6_xk2F1J4TuSRxk1MtLw@mail.gmail.com/
Fixes: 00bfe02f4796 ("gfs2: Fix mmap + page fault deadlocks for buffered I/O")
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/gfs2/file.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c
index 42fa4b5b81a0..eb5ea0262f3c 100644
--- a/fs/gfs2/file.c
+++ b/fs/gfs2/file.c
@@ -998,8 +998,6 @@ static ssize_t gfs2_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
 		if (leftover != window_size) {
 			if (gfs2_holder_queued(&gh))
 				goto retry_under_glock;
-			if (written)
-				goto out_uninit;
 			goto retry;
 		}
 	}
@@ -1076,8 +1074,6 @@ static ssize_t gfs2_file_buffered_write(struct kiocb *iocb,
 			from->count = min(from->count, window_size - leftover);
 			if (gfs2_holder_queued(gh))
 				goto retry_under_glock;
-			if (read && !(iocb->ki_flags & IOCB_DIRECT))
-				goto out_uninit;
 			goto retry;
 		}
 	}
-- 
2.35.1