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Message-ID: <20241008095606.990466-1-hsiangkao@linux.alibaba.com>
Date: Tue, 8 Oct 2024 17:56:05 +0800
From: Gao Xiang <hsiangkao@...ux.alibaba.com>
To: Christian Brauner <brauner@...nel.org>,
Alexander Viro <viro@...iv.linux.org.uk>,
Jan Kara <jack@...e.cz>
Cc: Allison Karlitskaya <allison.karlitskaya@...hat.com>,
Chao Yu <chao@...nel.org>,
LKML <linux-kernel@...r.kernel.org>,
linux-fsdevel@...r.kernel.org,
linux-erofs@...ts.ozlabs.org,
Gao Xiang <hsiangkao@...ux.alibaba.com>
Subject: [PATCH 1/2] fs/super.c: introduce get_tree_bdev_by_dev()
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_by_dev() to specify a device number explicitly
instead of the hardcoded fc->source as mentioned in [2], there are
other benefits like:
- Filesystems can have other ways to get a bdev-based sb
in addition to the current hard-coded source path;
- Pseudo-filesystems can utilize this method to generate a
filesystem from given device numbers too.
- Like get_tree_nodev(), it doesn't strictly tie to fc->source
either.
[1] https://lore.kernel.org/r/CAOYeF9VQ8jKVmpy5Zy9DNhO6xmWSKMB-DO8yvBB0XvBE7=3Ugg@mail.gmail.com
[2] https://lore.kernel.org/r/b9565874-7018-46ef-b123-b524a1dffb21@linux.alibaba.com
Signed-off-by: Gao Xiang <hsiangkao@...ux.alibaba.com>
---
fs/super.c | 41 ++++++++++++++++++++++++++------------
include/linux/fs_context.h | 3 +++
2 files changed, 31 insertions(+), 13 deletions(-)
diff --git a/fs/super.c b/fs/super.c
index 1db230432960..8cc8350b9ba6 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -1596,26 +1596,17 @@ 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_by_dev - Get a bdev-based superblock with a given device number
* @fc: The filesystem context holding the parameters
* @fill_super: Helper to initialise a new superblock
+ * @dev: The device number indicating the target block device
*/
-int get_tree_bdev(struct fs_context *fc,
+int get_tree_bdev_by_dev(struct fs_context *fc,
int (*fill_super)(struct super_block *,
- struct fs_context *))
+ struct fs_context *), dev_t dev)
{
struct super_block *s;
int error = 0;
- dev_t dev;
-
- if (!fc->source)
- return invalf(fc, "No source specified");
-
- error = lookup_bdev(fc->source, &dev);
- if (error) {
- errorf(fc, "%s: Can't lookup blockdev", fc->source);
- return error;
- }
fc->sb_flags |= SB_NOSEC;
s = sget_dev(fc, dev);
@@ -1644,6 +1635,30 @@ int get_tree_bdev(struct fs_context *fc,
fc->root = dget(s->s_root);
return 0;
}
+EXPORT_SYMBOL_GPL(get_tree_bdev_by_dev);
+
+/**
+ * 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 *))
+{
+ int error;
+ dev_t dev;
+
+ if (!fc->source)
+ return invalf(fc, "No source specified");
+
+ error = lookup_bdev(fc->source, &dev);
+ if (error) {
+ errorf(fc, "%s: Can't lookup blockdev", fc->source);
+ return error;
+ }
+ return get_tree_bdev_by_dev(fc, fill_super, dev);
+}
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 c13e99cbbf81..54f23589ad5b 100644
--- a/include/linux/fs_context.h
+++ b/include/linux/fs_context.h
@@ -160,6 +160,9 @@ extern int get_tree_keyed(struct fs_context *fc,
int setup_bdev_super(struct super_block *sb, int sb_flags,
struct fs_context *fc);
+int get_tree_bdev_by_dev(struct fs_context *fc,
+ int (*fill_super)(struct super_block *sb,
+ struct fs_context *fc), dev_t dev);
extern int get_tree_bdev(struct fs_context *fc,
int (*fill_super)(struct super_block *sb,
struct fs_context *fc));
--
2.43.5
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