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From:   Hsin-Yi Wang <hsinyi@chromium.org>
To:     Phillip Lougher <phillip@squashfs.org.uk>,
        Matthew Wilcox <willy@infradead.org>,
        Xiongwei Song <Xiongwei.Song@windriver.com>
Cc:     Zheng Liang <zhengliang6@huawei.com>,
        Zhang Yi <yi.zhang@huawei.com>, Hou Tao <houtao1@huawei.com>,
        Miao Xie <miaoxie@huawei.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        "linux-mm @ kvack . org" <linux-mm@kvack.org>,
        "squashfs-devel @ lists . sourceforge . net" 
        <squashfs-devel@lists.sourceforge.net>,
        linux-kernel@vger.kernel.org
Subject: [PATCH 1/2] Revert "squashfs: provide backing_dev_info in order to disable read-ahead"
Date:   Mon, 16 May 2022 18:51:01 +0800
Message-Id: <20220516105100.1412740-2-hsinyi@chromium.org>
In-Reply-To: <20220516105100.1412740-1-hsinyi@chromium.org>
References: <20220516105100.1412740-1-hsinyi@chromium.org>
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This reverts commit 9eec1d897139e5de287af5d559a02b811b844d82.

Revert closing the readahead to squashfs since the readahead callback
for squashfs is implemented.

Suggested-by: Xiongwei Song <sxwjean@gmail.com>
Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
---
 fs/squashfs/super.c | 33 ---------------------------------
 1 file changed, 33 deletions(-)

diff --git a/fs/squashfs/super.c b/fs/squashfs/super.c
index 6d594ba2ed28..32565dafa7f3 100644
--- a/fs/squashfs/super.c
+++ b/fs/squashfs/super.c
@@ -29,7 +29,6 @@
 #include <linux/module.h>
 #include <linux/magic.h>
 #include <linux/xattr.h>
-#include <linux/backing-dev.h>
 
 #include "squashfs_fs.h"
 #include "squashfs_fs_sb.h"
@@ -113,24 +112,6 @@ static const struct squashfs_decompressor *supported_squashfs_filesystem(
 	return decompressor;
 }
 
-static int squashfs_bdi_init(struct super_block *sb)
-{
-	int err;
-	unsigned int major = MAJOR(sb->s_dev);
-	unsigned int minor = MINOR(sb->s_dev);
-
-	bdi_put(sb->s_bdi);
-	sb->s_bdi = &noop_backing_dev_info;
-
-	err = super_setup_bdi_name(sb, "squashfs_%u_%u", major, minor);
-	if (err)
-		return err;
-
-	sb->s_bdi->ra_pages = 0;
-	sb->s_bdi->io_pages = 0;
-
-	return 0;
-}
 
 static int squashfs_fill_super(struct super_block *sb, struct fs_context *fc)
 {
@@ -146,20 +127,6 @@ static int squashfs_fill_super(struct super_block *sb, struct fs_context *fc)
 
 	TRACE("Entered squashfs_fill_superblock\n");
 
-	/*
-	 * squashfs provides 'backing_dev_info' in order to disable read-ahead. For
-	 * squashfs, I/O is not deferred, it is done immediately in read_folio,
-	 * which means the user would always have to wait their own I/O. So the effect
-	 * of readahead is very weak for squashfs. squashfs_bdi_init will set
-	 * sb->s_bdi->ra_pages and sb->s_bdi->io_pages to 0 and close readahead for
-	 * squashfs.
-	 */
-	err = squashfs_bdi_init(sb);
-	if (err) {
-		errorf(fc, "squashfs init bdi failed");
-		return err;
-	}
-
 	sb->s_fs_info = kzalloc(sizeof(*msblk), GFP_KERNEL);
 	if (sb->s_fs_info == NULL) {
 		ERROR("Failed to allocate squashfs_sb_info\n");
-- 
2.36.0.550.gb090851708-goog