Revert "squashfs: provide backing_dev_info in order to disable read-ahead"

Patch series "Implement readahead for squashfs", v7.

Commit 9eec1d897139("squashfs: provide backing_dev_info in order to
disable read-ahead") mitigates the performance drop issue for squashfs by
closing readahead for it.

This series implements readahead callback for squashfs.

This patch (of 4):

This reverts 9eec1d897139e5 ("squashfs: provide backing_dev_info in order
to disable read-ahead").

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

Link: https://lkml.kernel.org/r/20220617083810.337573-1-hsinyi@chromium.org
Link: https://lkml.kernel.org/r/20220617083810.337573-2-hsinyi@chromium.org
Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
Suggested-by: Xiongwei Song <Xiongwei.Song@windriver.com>
Cc: Phillip Lougher <phillip@squashfs.org.uk>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Zheng Liang <zhengliang6@huawei.com>
Cc: Zhang Yi <yi.zhang@huawei.com>
Cc: Hou Tao <houtao1@huawei.com>
Cc: Miao Xie <miaoxie@huawei.com>
Cc: kernel test robot <lkp@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/fs/squashfs/super.c b/fs/squashfs/super.c
index 6d594ba..32565da 100644 (file)
--- 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");