fs/super.c: introduce get_tree_bdev_flags()

As Allison reported [1], currently get_tree_bdev() will store
"Can't lookup blockdev" error message.  Although it makes sense for
pure bdev-based fses, this message may mislead users who try to use
EROFS file-backed mounts since get_tree_nodev() is used as a fallback
then.

Add get_tree_bdev_flags() to specify extensible flags [2] and
GET_TREE_BDEV_QUIET_LOOKUP to silence "Can't lookup blockdev" message
since it's misleading to EROFS file-backed mounts now.

[1] https://lore.kernel.org/r/CAOYeF9VQ8jKVmpy5Zy9DNhO6xmWSKMB-DO8yvBB0XvBE7=3Ugg@mail.gmail.com
[2] https://lore.kernel.org/r/ZwUkJEtwIpUA4qMz@infradead.org

Suggested-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20241009033151.2334888-1-hsiangkao@linux.alibaba.com
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/super.c b/fs/super.c
index 1db230432960dca184f4b0ac61aa3553e15bdef9..c9c7223bc2a2e9cb5391a1b3a291f724416289c2 100644 (file)
--- a/fs/super.c
+++ b/fs/super.c
@@ -1596,13 +1596,14 @@ int setup_bdev_super(struct super_block *sb, int sb_flags,
 EXPORT_SYMBOL_GPL(setup_bdev_super);
 
 /**
- * get_tree_bdev - Get a superblock based on a single block device
+ * get_tree_bdev_flags - Get a superblock based on a single block device
  * @fc: The filesystem context holding the parameters
  * @fill_super: Helper to initialise a new superblock
+ * @flags: GET_TREE_BDEV_* flags
  */
-int get_tree_bdev(struct fs_context *fc,
-               int (*fill_super)(struct super_block *,
-                                 struct fs_context *))
+int get_tree_bdev_flags(struct fs_context *fc,
+               int (*fill_super)(struct super_block *sb,
+                                 struct fs_context *fc), unsigned int flags)
 {
        struct super_block *s;
        int error = 0;
@@ -1613,10 +1614,10 @@ int get_tree_bdev(struct fs_context *fc,
 
        error = lookup_bdev(fc->source, &dev);
        if (error) {
-               errorf(fc, "%s: Can't lookup blockdev", fc->source);
+               if (!(flags & GET_TREE_BDEV_QUIET_LOOKUP))
+                       errorf(fc, "%s: Can't lookup blockdev", fc->source);
                return error;
        }
-
        fc->sb_flags |= SB_NOSEC;
        s = sget_dev(fc, dev);
        if (IS_ERR(s))
@@ -1644,6 +1645,19 @@ int get_tree_bdev(struct fs_context *fc,
        fc->root = dget(s->s_root);
        return 0;
 }
+EXPORT_SYMBOL_GPL(get_tree_bdev_flags);
+
+/**
+ * get_tree_bdev - Get a superblock based on a single block device
+ * @fc: The filesystem context holding the parameters
+ * @fill_super: Helper to initialise a new superblock
+ */
+int get_tree_bdev(struct fs_context *fc,
+               int (*fill_super)(struct super_block *,
+                                 struct fs_context *))
+{
+       return get_tree_bdev_flags(fc, fill_super, 0);
+}
 EXPORT_SYMBOL(get_tree_bdev);
 
 static int test_bdev_super(struct super_block *s, void *data)

diff --git a/include/linux/fs_context.h b/include/linux/fs_context.h
index c13e99cbbf8162bb395a48f3709cbd69ac009e7d..4b4bfef6f053a49557118c3592ef64fc7ce1ab39 100644 (file)
--- a/include/linux/fs_context.h
+++ b/include/linux/fs_context.h
@@ -160,6 +160,12 @@ extern int get_tree_keyed(struct fs_context *fc,
 
 int setup_bdev_super(struct super_block *sb, int sb_flags,
                struct fs_context *fc);
+
+#define GET_TREE_BDEV_QUIET_LOOKUP             0x0001
+int get_tree_bdev_flags(struct fs_context *fc,
+               int (*fill_super)(struct super_block *sb,
+                                 struct fs_context *fc), unsigned int flags);
+
 extern int get_tree_bdev(struct fs_context *fc,
                               int (*fill_super)(struct super_block *sb,
                                                 struct fs_context *fc));