On 10/28/24 4:43 PM, Kalesh Singh wrote:
Commit 78ff64081949 ("vfs: Convert tracefs to use the new mount API") tracefs to use the new mount APIs caused mounting with the gid=<gid> option to not take effect.
Or any other mount options. I'm sure this isn't unique to gid, right? So, might want to fix the commit title.
The tracefs superblock can be updated from multiple paths: - on fs_initcall() to init_trace_printk_function_export() - form a work queue to initialize eventfs tracer_init_tracefs_work_func() - fsconfig() syscall to mount of remount sysfs
The tracefs super block root inode gets created early on in init_trace_printk_function_export().
With the new mount API tracefs effectively uses get_tree_single() instead of the old API mount_single().
Previously, mount_single() ensured that the options are alway applied to the superblock root inode: (1) If the root inode didn't exist, called fill_super() to create it and apply the options. (2) If the root inode exists, called reconfigure_single() which effectively called tracefs_apply_options() to parse and apply options to the subperblock's fs_info and inode and remount eventfs (if necessary)
On the other hand, get_tree_single() effectively calls vfs_get_super() which: (3) If the root inode doesn't exists calls fill_super() to create it and apply the options. (4) If the root inode already exists, updates the fs_context root with the superblock's root inode.
I'm honestly a little lost here, but given the differences between mount_single() and get_tree_single() - are other get_tree_single() users similarly broken?
Should get_tree_single() just be calling reconfigure_single() internally like mount_single() did? The comment in reconfigure_single() confuses me.
(4) above is always the case for tracefs mounts, since the super block's root inode will already be created by init_trace_printk_function_export().
this reminds me a little of
commit a6097180d884ddab769fb25588ea8598589c218c Author: NeilBrown neilb@suse.de Date: Mon Jan 17 09:07:26 2022 +1100
devtmpfs regression fix: reconfigure on each mount
This means that the gid mount option gets ignored: - Since it isn't applied to the super block's root inode, it doesn't get inherited by the children. - Since eventfs is initialized from form a separate work queue and before call to mount with the options, and it doesn't get remounted for mount.
Ensure that the mount options are applied to the super block and eventfs is remounted to respect the new mount options.
[1] https://lore.kernel.org/r/536e99d3-345c-448b-adee-a21389d7ab4b@redhat.com/
Fixes: 78ff64081949 ("vfs: Convert tracefs to use the new mount API") Cc: David Howells dhowells@redhat.com Cc: Steven Rostedt rostedt@goodmis.org Cc: Masami Hiramatsu mhiramat@kernel.org Signed-off-by: Kalesh Singh kaleshsingh@google.com
fs/tracefs/inode.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c index 1748dff58c3b..cfc614c638da 100644 --- a/fs/tracefs/inode.c +++ b/fs/tracefs/inode.c @@ -392,6 +392,9 @@ static int tracefs_reconfigure(struct fs_context *fc) struct tracefs_fs_info *sb_opts = sb->s_fs_info; struct tracefs_fs_info *new_opts = fc->s_fs_info;
- if (!new_opts)
return 0;
Can this really happen?
- sync_filesystem(sb); /* structure copy of new mount options to sb */ *sb_opts = *new_opts;
FWIW doing this as a structure copy was probably a terrible choice on my part. :(
@@ -478,14 +481,17 @@ static int tracefs_fill_super(struct super_block *sb, struct fs_context *fc) sb->s_op = &tracefs_super_operations; sb->s_d_op = &tracefs_dentry_operations;
- tracefs_apply_options(sb, false);
- return 0;
} static int tracefs_get_tree(struct fs_context *fc) {
- return get_tree_single(fc, tracefs_fill_super);
- int err = get_tree_single(fc, tracefs_fill_super);
- if (err)
return err;- return tracefs_reconfigure(fc);
} static void tracefs_free_fc(struct fs_context *fc)