linux-ext4 - [PATCH 5/6] btrfs: remove BTRFS_INODE_READDIO_NEED

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Date:   Wed,  8 Jul 2020 16:19:25 -0500
From:   Goldwyn Rodrigues <rgoldwyn@...e.de>
To:     linux-btrfs@...r.kernel.org
Cc:     linux-fsdevel@...r.kernel.org, darrick.wong@...cle.com, hch@....de,
        cluster-devel@...hat.com, linux-ext4@...r.kernel.org,
        linux-xfs@...r.kernel.org, Goldwyn Rodrigues <rgoldwyn@...e.com>,
        Nikolay Borisov <nborisov@...e.com>,
        Johannes Thumshirn <jth@...nel.org>
Subject: [PATCH 5/6] btrfs: remove BTRFS_INODE_READDIO_NEED_LOCK

From: Goldwyn Rodrigues <rgoldwyn@...e.com>

Since we now perform direct reads using i_rwsem, we can remove this
inode flag used to co-ordinate unlocked reads.

The truncate call takes i_rwsem. This means it is correctly synchronized
with concurrent direct reads.

Reviewed-by: Nikolay Borisov <nborisov@...e.com>
Reviewed-by: Johannes Thumshirn <jth@...nel.org>
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@...e.com>
---
 fs/btrfs/btrfs_inode.h | 18 ------------------
 fs/btrfs/inode.c       |  3 ---
 2 files changed, 21 deletions(-)

diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h
index e7d709505cb1..aeff56a0e105 100644
--- a/fs/btrfs/btrfs_inode.h
+++ b/fs/btrfs/btrfs_inode.h
@@ -28,7 +28,6 @@ enum {
 	BTRFS_INODE_NEEDS_FULL_SYNC,
 	BTRFS_INODE_COPY_EVERYTHING,
 	BTRFS_INODE_IN_DELALLOC_LIST,
-	BTRFS_INODE_READDIO_NEED_LOCK,
 	BTRFS_INODE_HAS_PROPS,
 	BTRFS_INODE_SNAPSHOT_FLUSH,
 };
@@ -313,23 +312,6 @@ struct btrfs_dio_private {
 	u8 csums[];
 };
 
-/*
- * Disable DIO read nolock optimization, so new dio readers will be forced
- * to grab i_mutex. It is used to avoid the endless truncate due to
- * nonlocked dio read.
- */
-static inline void btrfs_inode_block_unlocked_dio(struct btrfs_inode *inode)
-{
-	set_bit(BTRFS_INODE_READDIO_NEED_LOCK, &inode->runtime_flags);
-	smp_mb();
-}
-
-static inline void btrfs_inode_resume_unlocked_dio(struct btrfs_inode *inode)
-{
-	smp_mb__before_atomic();
-	clear_bit(BTRFS_INODE_READDIO_NEED_LOCK, &inode->runtime_flags);
-}
-
 /* Array of bytes with variable length, hexadecimal format 0x1234 */
 #define CSUM_FMT				"0x%*phN"
 #define CSUM_FMT_VALUE(size, bytes)		size, bytes
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 0fa75af35a1f..264b676ebf29 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -4835,10 +4835,7 @@ static int btrfs_setsize(struct inode *inode, struct iattr *attr)
 
 		truncate_setsize(inode, newsize);
 
-		/* Disable nonlocked read DIO to avoid the endless truncate */
-		btrfs_inode_block_unlocked_dio(BTRFS_I(inode));
 		inode_dio_wait(inode);
-		btrfs_inode_resume_unlocked_dio(BTRFS_I(inode));
 
 		ret = btrfs_truncate(inode, newsize == oldsize);
 		if (ret && inode->i_nlink) {
-- 
2.26.2