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-rw-r--r--fs/squashfs/super.c33
1 files changed, 33 insertions, 0 deletions
diff --git a/fs/squashfs/super.c b/fs/squashfs/super.c
index bb44ff4c5cc6..b1b556dbce12 100644
--- a/fs/squashfs/super.c
+++ b/fs/squashfs/super.c
@@ -29,6 +29,7 @@
#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"
@@ -112,6 +113,24 @@ 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)
{
@@ -127,6 +146,20 @@ 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 readpage,
+ * 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");