FAILED: patch "[PATCH] btrfs: fix error handling when submitting direct I/O bio" failed to apply to 4.4-stable tree

The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 6d3113a193e3385c72240096fe397618ecab6e43 Mon Sep 17 00:00:00 2001
From: Omar Sandoval <[email protected]>
Date: Thu, 16 Apr 2020 14:46:12 -0700
Subject: [PATCH] btrfs: fix error handling when submitting direct I/O bio

In btrfs_submit_direct_hook(), if a direct I/O write doesn't span a RAID stripe or chunk, we submit orig_bio without cloning it. In this case, we don't increment pending_bios. Then, if btrfs_submit_dio_bio() fails, we decrement pending_bios to -1, and we never complete orig_bio. Fix it by initializing pending_bios to 1 instead of incrementing later.

Fixing this exposes another bug: we put orig_bio prematurely and then put it again from end_io. Fix it by not putting orig_bio.

After this change, pending_bios is really more of a reference count, but I'll leave that cleanup separate to keep the fix small.

index 259239b33370..b628c319a5b6 100644
@@ -7939,7 +7939,6 @@ static int btrfs_submit_direct_hook(struct btrfs_dio_private *dip)
 
 	/* bio split */
 	ASSERT(geom.len <= INT_MAX);
-	atomic_inc(&dip->pending_bios);
 	do {
 		clone_len = min_t(int, submit_len, geom.len);
 

@@ -7989,7 +7988,8 @@ static int btrfs_submit_direct_hook(struct btrfs_dio_private *dip)
 	if (!status)
 		return 0;
 
-	bio_put(bio);
+	if (bio != orig_bio)
+		bio_put(bio);
 out_err:
 	dip->errors = 1;
 	/*

@@ -8030,7 +8030,7 @@ static void btrfs_submit_direct(struct bio *dio_bio, struct inode *inode,
 	bio->bi_private = dip;
 	dip->orig_bio = bio;
 	dip->dio_bio = dio_bio;
-	atomic_set(&dip->pending_bios, 0);
+	atomic_set(&dip->pending_bios, 1);
 	io_bio = btrfs_io_bio(bio);
 	io_bio->logical = file_offset;