lkml.org 
[lkml]   [2018]   [Jan]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [RFC PATCH 03/17] tracefs: De-globalize instances' callbacks

    I just stumbled across this patch (and the following one). What purpose
    would this have? The "instances" directory is used to make multiple
    buffers. Why would we have more than one?

    -- Steve


    On Tue, 5 Sep 2017 16:30:12 +0300
    Alexander Shishkin <alexander.shishkin@linux.intel.com> wrote:

    > Currently, tracefs has exactly one special 'instances' subdirectory, where
    > the caller can have their own .mkdir/.rmdir callbacks, which allow the
    > caller to handle user's mkdir/rmdir inside that directory. Tracefs allows
    > one set of these callbacks (tracefs_dir_ops).
    >
    > This patch de-globalizes tracefs_dir_ops so that it's possible to have
    > multiple such subdirectories.
    >
    > Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
    > Cc: Steven Rostedt <rostedt@goodmis.org>
    > ---
    > fs/tracefs/inode.c | 35 +++++++++++++++++++++++++----------
    > 1 file changed, 25 insertions(+), 10 deletions(-)
    >
    > diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
    > index bea8ad876b..b14f03a655 100644
    > --- a/fs/tracefs/inode.c
    > +++ b/fs/tracefs/inode.c
    > @@ -50,10 +50,10 @@ static const struct file_operations tracefs_file_operations = {
    > .llseek = noop_llseek,
    > };
    >
    > -static struct tracefs_dir_ops {
    > +struct tracefs_dir_ops {
    > int (*mkdir)(const char *name);
    > int (*rmdir)(const char *name);
    > -} tracefs_ops;
    > +};
    >
    > static char *get_dname(struct dentry *dentry)
    > {
    > @@ -72,6 +72,7 @@ static char *get_dname(struct dentry *dentry)
    >
    > static int tracefs_syscall_mkdir(struct inode *inode, struct dentry *dentry, umode_t mode)
    > {
    > + struct tracefs_dir_ops *tracefs_ops = dentry->d_parent->d_fsdata;
    > char *name;
    > int ret;
    >
    > @@ -85,7 +86,7 @@ static int tracefs_syscall_mkdir(struct inode *inode, struct dentry *dentry, umo
    > * mkdir routine to handle races.
    > */
    > inode_unlock(inode);
    > - ret = tracefs_ops.mkdir(name);
    > + ret = tracefs_ops->mkdir(name);
    > inode_lock(inode);
    >
    > kfree(name);
    > @@ -95,6 +96,7 @@ static int tracefs_syscall_mkdir(struct inode *inode, struct dentry *dentry, umo
    >
    > static int tracefs_syscall_rmdir(struct inode *inode, struct dentry *dentry)
    > {
    > + struct tracefs_dir_ops *tracefs_ops = dentry->d_fsdata;
    > char *name;
    > int ret;
    >
    > @@ -112,7 +114,7 @@ static int tracefs_syscall_rmdir(struct inode *inode, struct dentry *dentry)
    > inode_unlock(inode);
    > inode_unlock(dentry->d_inode);
    >
    > - ret = tracefs_ops.rmdir(name);
    > + ret = tracefs_ops->rmdir(name);
    >
    > inode_lock_nested(inode, I_MUTEX_PARENT);
    > inode_lock(dentry->d_inode);
    > @@ -342,6 +344,9 @@ static struct dentry *start_creating(const char *name, struct dentry *parent)
    > if (IS_ERR(dentry)) {
    > inode_unlock(parent->d_inode);
    > simple_release_fs(&tracefs_mount, &tracefs_mount_count);
    > + } else {
    > + /* propagate dir ops */
    > + dentry->d_fsdata = parent->d_fsdata;
    > }
    >
    > return dentry;
    > @@ -482,18 +487,25 @@ struct dentry *tracefs_create_instance_dir(const char *name, struct dentry *pare
    > int (*mkdir)(const char *name),
    > int (*rmdir)(const char *name))
    > {
    > + struct tracefs_dir_ops *tracefs_ops = parent ? parent->d_fsdata : NULL;
    > struct dentry *dentry;
    >
    > - /* Only allow one instance of the instances directory. */
    > - if (WARN_ON(tracefs_ops.mkdir || tracefs_ops.rmdir))
    > + if (WARN_ON(tracefs_ops))
    > + return NULL;
    > +
    > + tracefs_ops = kzalloc(sizeof(*tracefs_ops), GFP_KERNEL);
    > + if (!tracefs_ops)
    > return NULL;
    >
    > dentry = __create_dir(name, parent, &tracefs_dir_inode_operations);
    > - if (!dentry)
    > + if (!dentry) {
    > + kfree(tracefs_ops);
    > return NULL;
    > + }
    >
    > - tracefs_ops.mkdir = mkdir;
    > - tracefs_ops.rmdir = rmdir;
    > + tracefs_ops->mkdir = mkdir;
    > + tracefs_ops->rmdir = rmdir;
    > + dentry->d_fsdata = tracefs_ops;
    >
    > return dentry;
    > }
    > @@ -513,8 +525,11 @@ static int __tracefs_remove(struct dentry *dentry, struct dentry *parent)
    > simple_unlink(parent->d_inode, dentry);
    > break;
    > }
    > - if (!ret)
    > + if (!ret) {
    > d_delete(dentry);
    > + if (dentry->d_fsdata != parent->d_fsdata)
    > + kfree(dentry->d_fsdata);
    > + }
    > dput(dentry);
    > }
    > }

    \
     
     \ /
      Last update: 2018-01-24 19:55    [W:4.840 / U:0.372 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site