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Message-ID: <20230731231707.328710408@goodmis.org>
Date: Mon, 31 Jul 2023 19:16:46 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: linux-kernel@...r.kernel.org
Cc: Masami Hiramatsu <mhiramat@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Andrew Morton <akpm@...ux-foundation.org>,
Ajay Kaher <akaher@...are.com>,
Ching-lin Yu <chinglinyu@...gle.com>
Subject: [for-next][PATCH 12/15] eventfs: Implement functions to create files and dirs when accessed
From: Ajay Kaher <akaher@...are.com>
Add create_file() and create_dir() functions to create the files and
directories respectively when they are accessed. The functions will be
called from the lookup operation of the inode_operations or from the open
function of file_operations.
Link: https://lkml.kernel.org/r/1690568452-46553-8-git-send-email-akaher@vmware.com
Signed-off-by: Ajay Kaher <akaher@...are.com>
Co-developed-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
Tested-by: Ching-lin Yu <chinglinyu@...gle.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
fs/tracefs/event_inode.c | 61 +++++++++++++++++++++++++++++++--
fs/tracefs/inode.c | 74 ++++++++++++++++++++++++++++++++++++++++
fs/tracefs/internal.h | 3 ++
3 files changed, 136 insertions(+), 2 deletions(-)
diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index 24d645c61029..5240bd2c81e7 100644
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -101,7 +101,34 @@ static struct dentry *create_file(const char *name, umode_t mode,
struct dentry *parent, void *data,
const struct file_operations *fop)
{
- return NULL;
+ struct tracefs_inode *ti;
+ struct dentry *dentry;
+ struct inode *inode;
+
+ if (!(mode & S_IFMT))
+ mode |= S_IFREG;
+
+ if (WARN_ON_ONCE(!S_ISREG(mode)))
+ return NULL;
+
+ dentry = eventfs_start_creating(name, parent);
+
+ if (IS_ERR(dentry))
+ return dentry;
+
+ inode = tracefs_get_inode(dentry->d_sb);
+ if (unlikely(!inode))
+ return eventfs_failed_creating(dentry);
+
+ inode->i_mode = mode;
+ inode->i_fop = fop;
+ inode->i_private = data;
+
+ ti = get_tracefs(inode);
+ ti->flags |= TRACEFS_EVENT_INODE;
+ d_instantiate(dentry, inode);
+ fsnotify_create(dentry->d_parent->d_inode, dentry);
+ return eventfs_end_creating(dentry);
};
/**
@@ -123,7 +150,31 @@ static struct dentry *create_file(const char *name, umode_t mode,
*/
static struct dentry *create_dir(const char *name, struct dentry *parent, void *data)
{
- return NULL;
+ struct tracefs_inode *ti;
+ struct dentry *dentry;
+ struct inode *inode;
+
+ dentry = eventfs_start_creating(name, parent);
+ if (IS_ERR(dentry))
+ return dentry;
+
+ inode = tracefs_get_inode(dentry->d_sb);
+ if (unlikely(!inode))
+ return eventfs_failed_creating(dentry);
+
+ inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
+ inode->i_op = &eventfs_root_dir_inode_operations;
+ inode->i_fop = &eventfs_file_operations;
+ inode->i_private = data;
+
+ ti = get_tracefs(inode);
+ ti->flags |= TRACEFS_EVENT_INODE;
+
+ inc_nlink(inode);
+ d_instantiate(dentry, inode);
+ inc_nlink(dentry->d_parent->d_inode);
+ fsnotify_mkdir(dentry->d_parent->d_inode, dentry);
+ return eventfs_end_creating(dentry);
}
/**
@@ -234,6 +285,12 @@ create_dentry(struct eventfs_file *ef, struct dentry *parent, bool lookup)
} else {
/* A race here, should try again (unless freed) */
invalidate = true;
+
+ /*
+ * Should never happen unless we get here due to being freed.
+ * Otherwise it means two dentries exist with the same name.
+ */
+ WARN_ON_ONCE(!ef->is_freed);
}
mutex_unlock(&eventfs_mutex);
if (invalidate)
diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
index 4acc4b4dfd22..d9273066f25f 100644
--- a/fs/tracefs/inode.c
+++ b/fs/tracefs/inode.c
@@ -474,6 +474,80 @@ struct dentry *tracefs_end_creating(struct dentry *dentry)
return dentry;
}
+/**
+ * eventfs_start_creating - start the process of creating a dentry
+ * @name: Name of the file created for the dentry
+ * @parent: The parent dentry where this dentry will be created
+ *
+ * This is a simple helper function for the dynamically created eventfs
+ * files. When the directory of the eventfs files are accessed, their
+ * dentries are created on the fly. This function is used to start that
+ * process.
+ */
+struct dentry *eventfs_start_creating(const char *name, struct dentry *parent)
+{
+ struct dentry *dentry;
+ int error;
+
+ error = simple_pin_fs(&trace_fs_type, &tracefs_mount,
+ &tracefs_mount_count);
+ if (error)
+ return ERR_PTR(error);
+
+ /*
+ * If the parent is not specified, we create it in the root.
+ * We need the root dentry to do this, which is in the super
+ * block. A pointer to that is in the struct vfsmount that we
+ * have around.
+ */
+ if (!parent)
+ parent = tracefs_mount->mnt_root;
+
+ if (unlikely(IS_DEADDIR(parent->d_inode)))
+ dentry = ERR_PTR(-ENOENT);
+ else
+ dentry = lookup_one_len(name, parent, strlen(name));
+
+ if (!IS_ERR(dentry) && dentry->d_inode) {
+ dput(dentry);
+ dentry = ERR_PTR(-EEXIST);
+ }
+
+ if (IS_ERR(dentry))
+ simple_release_fs(&tracefs_mount, &tracefs_mount_count);
+
+ return dentry;
+}
+
+/**
+ * eventfs_failed_creating - clean up a failed eventfs dentry creation
+ * @dentry: The dentry to clean up
+ *
+ * If after calling eventfs_start_creating(), a failure is detected, the
+ * resources created by eventfs_start_creating() needs to be cleaned up. In
+ * that case, this function should be called to perform that clean up.
+ */
+struct dentry *eventfs_failed_creating(struct dentry *dentry)
+{
+ dput(dentry);
+ simple_release_fs(&tracefs_mount, &tracefs_mount_count);
+ return NULL;
+}
+
+/**
+ * eventfs_end_creating - Finish the process of creating a eventfs dentry
+ * @dentry: The dentry that has successfully been created.
+ *
+ * This function is currently just a place holder to match
+ * eventfs_start_creating(). In case any synchronization needs to be added,
+ * this function will be used to implement that without having to modify
+ * the callers of eventfs_start_creating().
+ */
+struct dentry *eventfs_end_creating(struct dentry *dentry)
+{
+ return dentry;
+}
+
/**
* tracefs_create_file - create a file in the tracefs filesystem
* @name: a pointer to a string containing the name of the file to create.
diff --git a/fs/tracefs/internal.h b/fs/tracefs/internal.h
index 9bfad9d95a4a..69c2b1d87c46 100644
--- a/fs/tracefs/internal.h
+++ b/fs/tracefs/internal.h
@@ -21,6 +21,9 @@ struct dentry *tracefs_start_creating(const char *name, struct dentry *parent);
struct dentry *tracefs_end_creating(struct dentry *dentry);
struct dentry *tracefs_failed_creating(struct dentry *dentry);
struct inode *tracefs_get_inode(struct super_block *sb);
+struct dentry *eventfs_start_creating(const char *name, struct dentry *parent);
+struct dentry *eventfs_failed_creating(struct dentry *dentry);
+struct dentry *eventfs_end_creating(struct dentry *dentry);
void eventfs_set_ef_status_free(struct dentry *dentry);
#endif /* _TRACEFS_INTERNAL_H */
--
2.40.1
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