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 <[email protected]> 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/[email protected]/ > > Fixes: 78ff64081949 ("vfs: Convert tracefs to use the new mount API") > Cc: David Howells <[email protected]> > Cc: Steven Rostedt <[email protected]> > Cc: Masami Hiramatsu <[email protected]> > Signed-off-by: Kalesh Singh <[email protected]> > --- > 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)
