From: "Steven Rostedt (Google)" rostedt@goodmis.org

The "lookup" parameter is a way to differentiate the call to create_file/dir_dentry() from when it's just a lookup (no need to up the dentry refcount) and accessed via a readdir (need to up the refcount).

But reality, it just makes the code more complex. Just up the refcount and let the caller decide to dput() the result or not.

Link: https://lore.kernel.org/linux-trace-kernel/20240103102553.17a19cea@gandalf.l... Link: https://lore.kernel.org/linux-trace-kernel/20240104015435.517502710@goodmis....

Cc: Masami Hiramatsu mhiramat@kernel.org Cc: Mark Rutland mark.rutland@arm.com Cc: Mathieu Desnoyers mathieu.desnoyers@efficios.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Ajay Kaher akaher@vmware.com Cc: Al Viro viro@ZenIV.linux.org.uk Cc: Christian Brauner brauner@kernel.org Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org (cherry picked from commit b0f7e2d739b4aac131ea1662d086a07775097b05) --- fs/tracefs/event_inode.c | 55 +++++++++++++++------------------------- 1 file changed, 20 insertions(+), 35 deletions(-)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c index f0677ea0ec24..c360300fb866 100644 --- a/fs/tracefs/event_inode.c +++ b/fs/tracefs/event_inode.c @@ -390,16 +390,14 @@ void eventfs_set_ei_status_free(struct tracefs_inode *ti, struct dentry *dentry) * @mode: The mode of the file. * @data: The data to use to set the inode of the file with on open() * @fops: The fops of the file to be created. - * @lookup: If called by the lookup routine, in which case, dput() the created dentry. * * Create a dentry for a file of an eventfs_inode @ei and place it into the - * address located at @e_dentry. If the @e_dentry already has a dentry, then - * just do a dget() on it and return. Otherwise create the dentry and attach it. + * address located at @e_dentry. */ static struct dentry * create_file_dentry(struct eventfs_inode *ei, int idx, struct dentry *parent, const char *name, umode_t mode, void *data, - const struct file_operations *fops, bool lookup) + const struct file_operations *fops) { struct eventfs_attr *attr = NULL; struct dentry **e_dentry = &ei->d_children[idx]; @@ -414,9 +412,7 @@ create_file_dentry(struct eventfs_inode *ei, int idx, } /* If the e_dentry already has a dentry, use it */ if (*e_dentry) { - /* lookup does not need to up the ref count */ - if (!lookup) - dget(*e_dentry); + dget(*e_dentry); mutex_unlock(&eventfs_mutex); return *e_dentry; } @@ -441,13 +437,12 @@ create_file_dentry(struct eventfs_inode *ei, int idx, * way to being freed, don't return it. If e_dentry is NULL * it means it was already freed. */ - if (ei->is_freed) + if (ei->is_freed) { dentry = NULL; - else + } else { dentry = *e_dentry; - /* The lookup does not need to up the dentry refcount */ - if (dentry && !lookup) dget(dentry); + } mutex_unlock(&eventfs_mutex); return dentry; } @@ -465,9 +460,6 @@ create_file_dentry(struct eventfs_inode *ei, int idx, } mutex_unlock(&eventfs_mutex);

- if (lookup) - dput(dentry); - return dentry; }

@@ -500,13 +492,12 @@ static void eventfs_post_create_dir(struct eventfs_inode *ei) * @pei: The eventfs_inode parent of ei. * @ei: The eventfs_inode to create the directory for * @parent: The dentry of the parent of this directory - * @lookup: True if this is called by the lookup code * * This creates and attaches a directory dentry to the eventfs_inode @ei. */ static struct dentry * create_dir_dentry(struct eventfs_inode *pei, struct eventfs_inode *ei, - struct dentry *parent, bool lookup) + struct dentry *parent) { struct dentry *dentry = NULL;

@@ -518,11 +509,9 @@ create_dir_dentry(struct eventfs_inode *pei, struct eventfs_inode *ei, return NULL; } if (ei->dentry) { - /* If the dentry already has a dentry, use it */ + /* If the eventfs_inode already has a dentry, use it */ dentry = ei->dentry; - /* lookup does not need to up the ref count */ - if (!lookup) - dget(dentry); + dget(dentry); mutex_unlock(&eventfs_mutex); return dentry; } @@ -542,7 +531,7 @@ create_dir_dentry(struct eventfs_inode *pei, struct eventfs_inode *ei, * way to being freed. */ dentry = ei->dentry; - if (dentry && !lookup) + if (dentry) dget(dentry); mutex_unlock(&eventfs_mutex); return dentry; @@ -562,9 +551,6 @@ create_dir_dentry(struct eventfs_inode *pei, struct eventfs_inode *ei, } mutex_unlock(&eventfs_mutex);

- if (lookup) - dput(dentry); - return dentry; }

@@ -589,8 +575,8 @@ static struct dentry *eventfs_root_lookup(struct inode *dir, struct eventfs_inode *ei; struct dentry *ei_dentry = NULL; struct dentry *ret = NULL; + struct dentry *d; const char *name = dentry->d_name.name; - bool created = false; umode_t mode; void *data; int idx; @@ -626,13 +612,10 @@ static struct dentry *eventfs_root_lookup(struct inode *dir, ret = simple_lookup(dir, dentry, flags); if (IS_ERR(ret)) goto out; - create_dir_dentry(ei, ei_child, ei_dentry, true); - created = true; - break; - } - - if (created) + d = create_dir_dentry(ei, ei_child, ei_dentry); + dput(d); goto out; + }

for (i = 0; i < ei->nr_entries; i++) { entry = &ei->entries[i]; @@ -650,8 +633,8 @@ static struct dentry *eventfs_root_lookup(struct inode *dir, ret = simple_lookup(dir, dentry, flags); if (IS_ERR(ret)) goto out; - create_file_dentry(ei, i, ei_dentry, name, mode, cdata, - fops, true); + d = create_file_dentry(ei, i, ei_dentry, name, mode, cdata, fops); + dput(d); break; } } @@ -768,9 +751,10 @@ static int dcache_dir_open_wrapper(struct inode *inode, struct file *file) inode_lock(parent->d_inode); list_for_each_entry_srcu(ei_child, &ei->children, list, srcu_read_lock_held(&eventfs_srcu)) { - d = create_dir_dentry(ei, ei_child, parent, false); + d = create_dir_dentry(ei, ei_child, parent); if (d) { ret = add_dentries(&dentries, d, cnt); + dput(d); if (ret < 0) break; cnt++; @@ -790,9 +774,10 @@ static int dcache_dir_open_wrapper(struct inode *inode, struct file *file) mutex_unlock(&eventfs_mutex); if (r <= 0) continue; - d = create_file_dentry(ei, i, parent, name, mode, cdata, fops, false); + d = create_file_dentry(ei, i, parent, name, mode, cdata, fops); if (d) { ret = add_dentries(&dentries, d, cnt); + dput(d); if (ret < 0) break; cnt++;

From: "Steven Rostedt (Google)" rostedt@goodmis.org

Instead of walking the dentries on mount/remount to update the gid values of all the dentries if a gid option is specified on mount, just update the root inode. Add .getattr, .setattr, and .permissions on the tracefs inode operations to update the permissions of the files and directories.

For all files and directories in the top level instance:

/sys/kernel/tracing/*

It will use the root inode as the default permissions. The inode that represents: /sys/kernel/tracing (or wherever it is mounted).

When an instance is created:

mkdir /sys/kernel/tracing/instance/foo

The directory "foo" and all its files and directories underneath will use the default of what foo is when it was created. A remount of tracefs will not affect it.

If a user were to modify the permissions of any file or directory in tracefs, it will also no longer be modified by a change in ownership of a remount.

The events directory, if it is in the top level instance, will use the tracefs root inode as the default ownership for itself and all the files and directories below it.

For the events directory in an instance ("foo"), it will keep the ownership of what it was when it was created, and that will be used as the default ownership for the files and directories beneath it.

Link: https://lore.kernel.org/linux-trace-kernel/CAHk-=wjVdGkjDXBbvLn2wbZnqP4UsH46... Link: https://lore.kernel.org/linux-trace-kernel/20240103215016.1e0c9811@gandalf.l...

Cc: Masami Hiramatsu mhiramat@kernel.org Cc: Mathieu Desnoyers mathieu.desnoyers@efficios.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Al Viro viro@ZenIV.linux.org.uk Cc: Christian Brauner brauner@kernel.org Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org (cherry picked from commit 8186fff7ab649085e2c60d032d9a20a85af1d87c) --- fs/tracefs/event_inode.c | 79 +++++++++++++++- fs/tracefs/inode.c | 198 ++++++++++++++++++++++----------------- fs/tracefs/internal.h | 3 + 3 files changed, 190 insertions(+), 90 deletions(-)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c index 41af56f44f0a..72912b5f9a90 100644 --- a/fs/tracefs/event_inode.c +++ b/fs/tracefs/event_inode.c @@ -45,6 +45,7 @@ enum { EVENTFS_SAVE_MODE = BIT(16), EVENTFS_SAVE_UID = BIT(17), EVENTFS_SAVE_GID = BIT(18), + EVENTFS_TOPLEVEL = BIT(19), };

#define EVENTFS_MODE_MASK (EVENTFS_SAVE_MODE - 1) @@ -115,10 +116,17 @@ static int eventfs_set_attr(struct mnt_idmap *idmap, struct dentry *dentry, * The events directory dentry is never freed, unless its * part of an instance that is deleted. It's attr is the * default for its child files and directories. - * Do not update it. It's not used for its own mode or ownership + * Do not update it. It's not used for its own mode or ownership. */ - if (!ei->is_events) + if (ei->is_events) { + /* But it still needs to know if it was modified */ + if (iattr->ia_valid & ATTR_UID) + ei->attr.mode |= EVENTFS_SAVE_UID; + if (iattr->ia_valid & ATTR_GID) + ei->attr.mode |= EVENTFS_SAVE_GID; + } else { update_attr(&ei->attr, iattr); + }

} else { name = dentry->d_name.name; @@ -136,9 +144,66 @@ static int eventfs_set_attr(struct mnt_idmap *idmap, struct dentry *dentry, return ret; }

+static void update_top_events_attr(struct eventfs_inode *ei, struct dentry *dentry) +{ + struct inode *inode; + + /* Only update if the "events" was on the top level */ + if (!ei || !(ei->attr.mode & EVENTFS_TOPLEVEL)) + return; + + /* Get the tracefs root inode. */ + inode = d_inode(dentry->d_sb->s_root); + ei->attr.uid = inode->i_uid; + ei->attr.gid = inode->i_gid; +} + +static void set_top_events_ownership(struct inode *inode) +{ + struct tracefs_inode *ti = get_tracefs(inode); + struct eventfs_inode *ei = ti->private; + struct dentry *dentry; + + /* The top events directory doesn't get automatically updated */ + if (!ei || !ei->is_events || !(ei->attr.mode & EVENTFS_TOPLEVEL)) + return; + + dentry = ei->dentry; + + update_top_events_attr(ei, dentry); + + if (!(ei->attr.mode & EVENTFS_SAVE_UID)) + inode->i_uid = ei->attr.uid; + + if (!(ei->attr.mode & EVENTFS_SAVE_GID)) + inode->i_gid = ei->attr.gid; +} + +static int eventfs_get_attr(struct mnt_idmap *idmap, + const struct path *path, struct kstat *stat, + u32 request_mask, unsigned int flags) +{ + struct dentry *dentry = path->dentry; + struct inode *inode = d_backing_inode(dentry); + + set_top_events_ownership(inode); + + generic_fillattr(idmap, request_mask, inode, stat); + return 0; +} + +static int eventfs_permission(struct mnt_idmap *idmap, + struct inode *inode, int mask) +{ + set_top_events_ownership(inode); + return generic_permission(idmap, inode, mask); +} + static const struct inode_operations eventfs_root_dir_inode_operations = { .lookup = eventfs_root_lookup, .setattr = eventfs_set_attr, + .getattr = eventfs_get_attr, + .permission = eventfs_permission, };

static const struct inode_operations eventfs_file_inode_operations = { @@ -174,6 +239,8 @@ static struct eventfs_inode *eventfs_find_events(struct dentry *dentry) } while (!ei->is_events); mutex_unlock(&eventfs_mutex);

+ update_top_events_attr(ei, dentry); + return ei; }

@@ -887,6 +954,14 @@ struct eventfs_inode *eventfs_create_events_dir(const char *name, struct dentry uid = d_inode(dentry->d_parent)->i_uid; gid = d_inode(dentry->d_parent)->i_gid;

+ /* + * If the events directory is of the top instance, then parent + * is NULL. Set the attr.mode to reflect this and its permissions will + * default to the tracefs root dentry. + */ + if (!parent) + ei->attr.mode = EVENTFS_TOPLEVEL; + /* This is used as the default ownership of the files and directories */ ei->attr.uid = uid; ei->attr.gid = gid; diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c index bc86ffdb103b..e1b172c0e091 100644 --- a/fs/tracefs/inode.c +++ b/fs/tracefs/inode.c @@ -91,6 +91,7 @@ static int tracefs_syscall_mkdir(struct mnt_idmap *idmap, struct inode *inode, struct dentry *dentry, umode_t mode) { + struct tracefs_inode *ti; char *name; int ret;

@@ -98,6 +99,15 @@ static int tracefs_syscall_mkdir(struct mnt_idmap *idmap, if (!name) return -ENOMEM;

+ /* + * This is a new directory that does not take the default of + * the rootfs. It becomes the default permissions for all the + * files and directories underneath it. + */ + ti = get_tracefs(inode); + ti->flags |= TRACEFS_INSTANCE_INODE; + ti->private = inode; + /* * The mkdir call can call the generic functions that create * the files within the tracefs system. It is up to the individual @@ -141,10 +151,76 @@ static int tracefs_syscall_rmdir(struct inode *inode, struct dentry *dentry) return ret; }

-static const struct inode_operations tracefs_dir_inode_operations = { +static void set_tracefs_inode_owner(struct inode *inode) +{ + struct tracefs_inode *ti = get_tracefs(inode); + struct inode *root_inode = ti->private; + + /* + * If this inode has never been referenced, then update + * the permissions to the superblock. + */ + if (!(ti->flags & TRACEFS_UID_PERM_SET)) + inode->i_uid = root_inode->i_uid; + + if (!(ti->flags & TRACEFS_GID_PERM_SET)) + inode->i_gid = root_inode->i_gid; +} + +static int tracefs_permission(struct mnt_idmap *idmap, + struct inode *inode, int mask) +{ + set_tracefs_inode_owner(inode); + return generic_permission(idmap, inode, mask); +} + +static int tracefs_getattr(struct mnt_idmap *idmap, + const struct path *path, struct kstat *stat, + u32 request_mask, unsigned int flags) +{ + struct inode *inode = d_backing_inode(path->dentry); + + set_tracefs_inode_owner(inode); + generic_fillattr(idmap, request_mask, inode, stat); + return 0; +} + +static int tracefs_setattr(struct mnt_idmap *idmap, struct dentry *dentry, + struct iattr *attr) +{ + unsigned int ia_valid = attr->ia_valid; + struct inode *inode = d_inode(dentry); + struct tracefs_inode *ti = get_tracefs(inode); + + if (ia_valid & ATTR_UID) + ti->flags |= TRACEFS_UID_PERM_SET; + + if (ia_valid & ATTR_GID) + ti->flags |= TRACEFS_GID_PERM_SET; + + return simple_setattr(idmap, dentry, attr); +} + +static const struct inode_operations tracefs_instance_dir_inode_operations = { .lookup = simple_lookup, .mkdir = tracefs_syscall_mkdir, .rmdir = tracefs_syscall_rmdir, + .permission = tracefs_permission, + .getattr = tracefs_getattr, + .setattr = tracefs_setattr, +}; + +static const struct inode_operations tracefs_dir_inode_operations = { + .lookup = simple_lookup, + .permission = tracefs_permission, + .getattr = tracefs_getattr, + .setattr = tracefs_setattr, +}; + +static const struct inode_operations tracefs_file_inode_operations = { + .permission = tracefs_permission, + .getattr = tracefs_getattr, + .setattr = tracefs_setattr, };

struct inode *tracefs_get_inode(struct super_block *sb) @@ -183,87 +259,6 @@ struct tracefs_fs_info { struct tracefs_mount_opts mount_opts; };

-static void change_gid(struct dentry *dentry, kgid_t gid) -{ - if (!dentry->d_inode) - return; - dentry->d_inode->i_gid = gid; -} - -/* - * Taken from d_walk, but without he need for handling renames. - * Nothing can be renamed while walking the list, as tracefs - * does not support renames. This is only called when mounting - * or remounting the file system, to set all the files to - * the given gid. - */ -static void set_gid(struct dentry *parent, kgid_t gid) -{ - struct dentry *this_parent; - struct list_head *next; - - this_parent = parent; - spin_lock(&this_parent->d_lock); - - change_gid(this_parent, gid); -repeat: - next = this_parent->d_subdirs.next; -resume: - while (next != &this_parent->d_subdirs) { - struct tracefs_inode *ti; - struct list_head *tmp = next; - struct dentry *dentry = list_entry(tmp, struct dentry, d_child); - next = tmp->next; - - /* Note, getdents() can add a cursor dentry with no inode */ - if (!dentry->d_inode) - continue; - - spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); - - change_gid(dentry, gid); - - /* If this is the events directory, update that too */ - ti = get_tracefs(dentry->d_inode); - if (ti && (ti->flags & TRACEFS_EVENT_INODE)) - eventfs_update_gid(dentry, gid); - - if (!list_empty(&dentry->d_subdirs)) { - spin_unlock(&this_parent->d_lock); - spin_release(&dentry->d_lock.dep_map, _RET_IP_); - this_parent = dentry; - spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_); - goto repeat; - } - spin_unlock(&dentry->d_lock); - } - /* - * All done at this level ... ascend and resume the search. - */ - rcu_read_lock(); -ascend: - if (this_parent != parent) { - struct dentry *child = this_parent; - this_parent = child->d_parent; - - spin_unlock(&child->d_lock); - spin_lock(&this_parent->d_lock); - - /* go into the first sibling still alive */ - do { - next = child->d_child.next; - if (next == &this_parent->d_subdirs) - goto ascend; - child = list_entry(next, struct dentry, d_child); - } while (unlikely(child->d_flags & DCACHE_DENTRY_KILLED)); - rcu_read_unlock(); - goto resume; - } - rcu_read_unlock(); - spin_unlock(&this_parent->d_lock); - return; -} - static int tracefs_parse_options(char *data, struct tracefs_mount_opts *opts) { substring_t args[MAX_OPT_ARGS]; @@ -336,10 +331,8 @@ static int tracefs_apply_options(struct super_block *sb, bool remount) if (!remount || opts->opts & BIT(Opt_uid)) inode->i_uid = opts->uid;

- if (!remount || opts->opts & BIT(Opt_gid)) { - /* Set all the group ids to the mount option */ - set_gid(sb->s_root, opts->gid); - } + if (!remount || opts->opts & BIT(Opt_gid)) + inode->i_gid = opts->gid;

return 0; } @@ -573,6 +566,26 @@ struct dentry *eventfs_end_creating(struct dentry *dentry) return dentry; }

+/* Find the inode that this will use for default */ +static struct inode *instance_inode(struct dentry *parent, struct inode *inode) +{ + struct tracefs_inode *ti; + + /* If parent is NULL then use root inode */ + if (!parent) + return d_inode(inode->i_sb->s_root); + + /* Find the inode that is flagged as an instance or the root inode */ + while (!IS_ROOT(parent)) { + ti = get_tracefs(d_inode(parent)); + if (ti->flags & TRACEFS_INSTANCE_INODE) + break; + parent = parent->d_parent; + } + + return d_inode(parent); +} + /** * tracefs_create_file - create a file in the tracefs filesystem * @name: a pointer to a string containing the name of the file to create. @@ -603,6 +616,7 @@ struct dentry *tracefs_create_file(const char *name, umode_t mode, struct dentry *parent, void *data, const struct file_operations *fops) { + struct tracefs_inode *ti; struct dentry *dentry; struct inode *inode;

@@ -621,7 +635,11 @@ struct dentry *tracefs_create_file(const char *name, umode_t mode, if (unlikely(!inode)) return tracefs_failed_creating(dentry);

+ ti = get_tracefs(inode); + ti->private = instance_inode(parent, inode); + inode->i_mode = mode; + inode->i_op = &tracefs_file_inode_operations; inode->i_fop = fops ? fops : &tracefs_file_operations; inode->i_private = data; inode->i_uid = d_inode(dentry->d_parent)->i_uid; @@ -634,6 +652,7 @@ struct dentry *tracefs_create_file(const char *name, umode_t mode, static struct dentry *__create_dir(const char *name, struct dentry *parent, const struct inode_operations *ops) { + struct tracefs_inode *ti; struct dentry *dentry = tracefs_start_creating(name, parent); struct inode *inode;

@@ -651,6 +670,9 @@ static struct dentry *__create_dir(const char *name, struct dentry *parent, inode->i_uid = d_inode(dentry->d_parent)->i_uid; inode->i_gid = d_inode(dentry->d_parent)->i_gid;

+ ti = get_tracefs(inode); + ti->private = instance_inode(parent, inode); + /* directory inodes start off with i_nlink == 2 (for "." entry) */ inc_nlink(inode); d_instantiate(dentry, inode); @@ -681,7 +703,7 @@ struct dentry *tracefs_create_dir(const char *name, struct dentry *parent) if (security_locked_down(LOCKDOWN_TRACEFS)) return NULL;

- return __create_dir(name, parent, &simple_dir_inode_operations); + return __create_dir(name, parent, &tracefs_dir_inode_operations); }

/** @@ -712,7 +734,7 @@ __init struct dentry *tracefs_create_instance_dir(const char *name, if (WARN_ON(tracefs_ops.mkdir || tracefs_ops.rmdir)) return NULL;

- dentry = __create_dir(name, parent, &tracefs_dir_inode_operations); + dentry = __create_dir(name, parent, &tracefs_instance_dir_inode_operations); if (!dentry) return NULL;

diff --git a/fs/tracefs/internal.h b/fs/tracefs/internal.h index 42bdeb471a07..12b7d0150ae9 100644 --- a/fs/tracefs/internal.h +++ b/fs/tracefs/internal.h @@ -5,6 +5,9 @@ enum { TRACEFS_EVENT_INODE = BIT(1), TRACEFS_EVENT_TOP_INODE = BIT(2), + TRACEFS_GID_PERM_SET = BIT(3), + TRACEFS_UID_PERM_SET = BIT(4), + TRACEFS_INSTANCE_INODE = BIT(5), };

struct tracefs_inode {

From: "Steven Rostedt (Google)" rostedt@goodmis.org

In order to apply a shortcut to skip over the current ctx->pos immediately, by using the ei->entries array, the reading of that array should be first. Moving the array reading before the linked list reading will make the shortcut change diff nicer to read.

Link: https://lore.kernel.org/all/CAHk-=wiKwDUDv3+jCsv-uacDcHDVTYsXtBR9=6sGM5mqX+D... Link: https://lore.kernel.org/linux-trace-kernel/20240104220048.333115095@goodmis....

Cc: Masami Hiramatsu mhiramat@kernel.org Cc: Mark Rutland mark.rutland@arm.com Cc: Mathieu Desnoyers mathieu.desnoyers@efficios.com Cc: Andrew Morton akpm@linux-foundation.org Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Al Viro viro@zeniv.linux.org.uk Cc: Christian Brauner brauner@kernel.org Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org (cherry picked from commit 704f960dbee2f1634f4b4e16f208cb16eaf41c1e) --- fs/tracefs/event_inode.c | 46 ++++++++++++++++++++-------------------- 1 file changed, 23 insertions(+), 23 deletions(-)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c index c73fb1f7ddbc..a1934e0eea3b 100644 --- a/fs/tracefs/event_inode.c +++ b/fs/tracefs/event_inode.c @@ -752,8 +752,8 @@ static int eventfs_iterate(struct file *file, struct dir_context *ctx) * Need to create the dentries and inodes to have a consistent * inode number. */ - list_for_each_entry_srcu(ei_child, &ei->children, list, - srcu_read_lock_held(&eventfs_srcu)) { + for (i = 0; i < ei->nr_entries; i++) { + void *cdata = ei->data;

if (c > 0) { c--; @@ -762,23 +762,32 @@ static int eventfs_iterate(struct file *file, struct dir_context *ctx)

ctx->pos++;

- if (ei_child->is_freed) - continue; + entry = &ei->entries[i]; + name = entry->name;

- name = ei_child->name; + mutex_lock(&eventfs_mutex); + /* If ei->is_freed then just bail here, nothing more to do */ + if (ei->is_freed) { + mutex_unlock(&eventfs_mutex); + goto out_dec; + } + r = entry->callback(name, &mode, &cdata, &fops); + mutex_unlock(&eventfs_mutex); + if (r <= 0) + continue;

- dentry = create_dir_dentry(ei, ei_child, ei_dentry); + dentry = create_file_dentry(ei, i, ei_dentry, name, mode, cdata, fops); if (!dentry) goto out_dec; ino = dentry->d_inode->i_ino; dput(dentry);

- if (!dir_emit(ctx, name, strlen(name), ino, DT_DIR)) + if (!dir_emit(ctx, name, strlen(name), ino, DT_REG)) goto out_dec; }

- for (i = 0; i < ei->nr_entries; i++) { - void *cdata = ei->data; + list_for_each_entry_srcu(ei_child, &ei->children, list, + srcu_read_lock_held(&eventfs_srcu)) {

if (c > 0) { c--; @@ -787,27 +796,18 @@ static int eventfs_iterate(struct file *file, struct dir_context *ctx)

ctx->pos++;

- entry = &ei->entries[i]; - name = entry->name; - - mutex_lock(&eventfs_mutex); - /* If ei->is_freed then just bail here, nothing more to do */ - if (ei->is_freed) { - mutex_unlock(&eventfs_mutex); - goto out_dec; - } - r = entry->callback(name, &mode, &cdata, &fops); - mutex_unlock(&eventfs_mutex); - if (r <= 0) + if (ei_child->is_freed) continue;

- dentry = create_file_dentry(ei, i, ei_dentry, name, mode, cdata, fops); + name = ei_child->name; + + dentry = create_dir_dentry(ei, ei_child, ei_dentry); if (!dentry) goto out_dec; ino = dentry->d_inode->i_ino; dput(dentry);

- if (!dir_emit(ctx, name, strlen(name), ino, DT_REG)) + if (!dir_emit(ctx, name, strlen(name), ino, DT_DIR)) goto out_dec; } ret = 1;

From: "Steven Rostedt (Google)" rostedt@goodmis.org

The dentries and inodes are created in the readdir for the sole purpose of getting a consistent inode number. Linus stated that is unnecessary, and that all inodes can have the same inode number. For a virtual file system they are pretty meaningless.

Instead use a single unique inode number for all files and one for all directories.

Link: https://lore.kernel.org/all/20240116133753.2808d45e@gandalf.local.home/ Link: https://lore.kernel.org/linux-trace-kernel/20240116211353.412180363@goodmis....

Cc: Masami Hiramatsu mhiramat@kernel.org Cc: Mark Rutland mark.rutland@arm.com Cc: Mathieu Desnoyers mathieu.desnoyers@efficios.com Cc: Christian Brauner brauner@kernel.org Cc: Al Viro viro@ZenIV.linux.org.uk Cc: Ajay Kaher ajay.kaher@broadcom.com Suggested-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org (cherry picked from commit 53c41052ba3121761e6f62a813961164532a214f) --- fs/tracefs/event_inode.c | 10 ++++++++++ 1 file changed, 10 insertions(+)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c index fdff53d5a1f8..5edf0b96758b 100644 --- a/fs/tracefs/event_inode.c +++ b/fs/tracefs/event_inode.c @@ -32,6 +32,10 @@ */ static DEFINE_MUTEX(eventfs_mutex);

+/* Choose something "unique" ;-) */ +#define EVENTFS_FILE_INODE_INO 0x12c4e37 +#define EVENTFS_DIR_INODE_INO 0x134b2f5 + /* * The eventfs_inode (ei) itself is protected by SRCU. It is released from * its parent's list and will have is_freed set (under eventfs_mutex). @@ -352,6 +356,9 @@ static struct dentry *create_file(const char *name, umode_t mode, inode->i_fop = fop; inode->i_private = data;

+ /* All files will have the same inode number */ + inode->i_ino = EVENTFS_FILE_INODE_INO; + ti = get_tracefs(inode); ti->flags |= TRACEFS_EVENT_INODE; d_instantiate(dentry, inode); @@ -388,6 +395,9 @@ static struct dentry *create_dir(struct eventfs_inode *ei, struct dentry *parent inode->i_op = &eventfs_root_dir_inode_operations; inode->i_fop = &eventfs_file_operations;

+ /* All directories will have the same inode number */ + inode->i_ino = EVENTFS_DIR_INODE_INO; + ti = get_tracefs(inode); ti->flags |= TRACEFS_EVENT_INODE;

From: Erick Archer erick.archer@gmx.com

As noted in the "Deprecated Interfaces, Language Features, Attributes, and Conventions" documentation [1], size calculations (especially multiplication) should not be performed in memory allocator (or similar) function arguments due to the risk of them overflowing. This could lead to values wrapping around and a smaller allocation being made than the caller was expecting. Using those allocations could lead to linear overflows of heap memory and other misbehaviors.

So, use the purpose specific kcalloc() function instead of the argument size * count in the kzalloc() function.

[1] https://www.kernel.org/doc/html/next/process/deprecated.html#open-coded-arit...

Link: https://lore.kernel.org/linux-trace-kernel/20240115181658.4562-1-erick.arche...

Cc: Masami Hiramatsu mhiramat@kernel.org Cc: Mathieu Desnoyers mathieu.desnoyers@efficios.com Cc: Mark Rutland mark.rutland@arm.com Link: https://github.com/KSPP/linux/issues/162 Signed-off-by: Erick Archer erick.archer@gmx.com Reviewed-by: Gustavo A. R. Silva gustavoars@kernel.org Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org (cherry picked from commit 1057066009c4325bb1d8430c9274894d0860e7c3) --- fs/tracefs/event_inode.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c index 10580d6b5012..6795fda2af19 100644 --- a/fs/tracefs/event_inode.c +++ b/fs/tracefs/event_inode.c @@ -97,7 +97,7 @@ static int eventfs_set_attr(struct mnt_idmap *idmap, struct dentry *dentry, /* Preallocate the children mode array if necessary */ if (!(dentry->d_inode->i_mode & S_IFDIR)) { if (!ei->entry_attrs) { - ei->entry_attrs = kzalloc(sizeof(*ei->entry_attrs) * ei->nr_entries, + ei->entry_attrs = kcalloc(ei->nr_entries, sizeof(*ei->entry_attrs), GFP_NOFS); if (!ei->entry_attrs) { ret = -ENOMEM; @@ -874,7 +874,7 @@ struct eventfs_inode *eventfs_create_dir(const char *name, struct eventfs_inode }

if (size) { - ei->d_children = kzalloc(sizeof(*ei->d_children) * size, GFP_KERNEL); + ei->d_children = kcalloc(size, sizeof(*ei->d_children), GFP_KERNEL); if (!ei->d_children) { kfree_const(ei->name); kfree(ei); @@ -941,7 +941,7 @@ struct eventfs_inode *eventfs_create_events_dir(const char *name, struct dentry goto fail;

if (size) { - ei->d_children = kzalloc(sizeof(*ei->d_children) * size, GFP_KERNEL); + ei->d_children = kcalloc(size, sizeof(*ei->d_children), GFP_KERNEL); if (!ei->d_children) goto fail; }

From: Linus Torvalds torvalds@linux-foundation.org

The 'eventfs_update_gid()' function is no longer called, so remove it (and the helper function it uses).

Link: https://lore.kernel.org/all/CAHk-=wj+DsZZ=2iTUkJ-Nojs9fjYMvPs1NuoM3yK7aTDtJf...

Fixes: 8186fff7ab64 ("tracefs/eventfs: Use root and instance inodes as default ownership") Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org (cherry picked from commit 29142dc92c37d3259a33aef15b03e6ee25b0d188) --- fs/tracefs/event_inode.c | 38 -------------------------------------- fs/tracefs/internal.h | 1 - 2 files changed, 39 deletions(-)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c index 6b211522a13e..1c3dd0ad4660 100644 --- a/fs/tracefs/event_inode.c +++ b/fs/tracefs/event_inode.c @@ -281,44 +281,6 @@ static void update_inode_attr(struct dentry *dentry, struct inode *inode, inode->i_gid = attr->gid; }

-static void update_gid(struct eventfs_inode *ei, kgid_t gid, int level) -{ - struct eventfs_inode *ei_child; - - /* at most we have events/system/event */ - if (WARN_ON_ONCE(level > 3)) - return; - - ei->attr.gid = gid; - - if (ei->entry_attrs) { - for (int i = 0; i < ei->nr_entries; i++) { - ei->entry_attrs[i].gid = gid; - } - } - - /* - * Only eventfs_inode with dentries are updated, make sure - * all eventfs_inodes are updated. If one of the children - * do not have a dentry, this function must traverse it. - */ - list_for_each_entry_srcu(ei_child, &ei->children, list, - srcu_read_lock_held(&eventfs_srcu)) { - if (!ei_child->dentry) - update_gid(ei_child, gid, level + 1); - } -} - -void eventfs_update_gid(struct dentry *dentry, kgid_t gid) -{ - struct eventfs_inode *ei = dentry->d_fsdata; - int idx; - - idx = srcu_read_lock(&eventfs_srcu); - update_gid(ei, gid, 0); - srcu_read_unlock(&eventfs_srcu, idx); -} - /** * create_file - create a file in the tracefs filesystem * @name: the name of the file to create. diff --git a/fs/tracefs/internal.h b/fs/tracefs/internal.h index 45397df9bb65..91c2bf0b91d9 100644 --- a/fs/tracefs/internal.h +++ b/fs/tracefs/internal.h @@ -82,7 +82,6 @@ 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_update_gid(struct dentry *dentry, kgid_t gid); void eventfs_set_ei_status_free(struct tracefs_inode *ti, struct dentry *dentry);

#endif /* _TRACEFS_INTERNAL_H */

From: Linus Torvalds torvalds@linux-foundation.org

The tracefs-specific fields in the inode were not initialized before the inode was exposed to others through the dentry with 'd_instantiate()'.

Move the field initializations up to before the d_instantiate.

Link: https://lore.kernel.org/linux-trace-kernel/20240131185512.478449628@goodmis....

Cc: stable@vger.kernel.org Cc: Masami Hiramatsu mhiramat@kernel.org Cc: Mark Rutland mark.rutland@arm.com Cc: Mathieu Desnoyers mathieu.desnoyers@efficios.com Cc: Christian Brauner brauner@kernel.org Cc: Al Viro viro@ZenIV.linux.org.uk Cc: Ajay Kaher ajay.kaher@broadcom.com Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Fixes: 5790b1fb3d672 ("eventfs: Remove eventfs_file and just use eventfs_inode") Reported-by: kernel test robot oliver.sang@intel.com Closes: https://lore.kernel.org/oe-lkp/202401291043.e62e89dc-oliver.sang@intel.com Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org (cherry picked from commit 4fa4b010b83fb2f837b5ef79e38072a79e96e4f1) --- fs/tracefs/event_inode.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c index 1c3dd0ad4660..824b1811e342 100644 --- a/fs/tracefs/event_inode.c +++ b/fs/tracefs/event_inode.c @@ -370,6 +370,8 @@ static struct dentry *create_dir(struct eventfs_inode *ei, struct dentry *parent

ti = get_tracefs(inode); ti->flags |= TRACEFS_EVENT_INODE; + /* Only directories have ti->private set to an ei, not files */ + ti->private = ei;

inc_nlink(inode); d_instantiate(dentry, inode); @@ -515,7 +517,6 @@ create_file_dentry(struct eventfs_inode *ei, int idx, static void eventfs_post_create_dir(struct eventfs_inode *ei) { struct eventfs_inode *ei_child; - struct tracefs_inode *ti;

lockdep_assert_held(&eventfs_mutex);

@@ -525,9 +526,6 @@ static void eventfs_post_create_dir(struct eventfs_inode *ei) srcu_read_lock_held(&eventfs_srcu)) { ei_child->d_parent = ei->dentry; } - - ti = get_tracefs(ei->dentry->d_inode); - ti->private = ei; }

/**

From: Linus Torvalds torvalds@linux-foundation.org

The dentry lookup for eventfs files was very broken, and had lots of signs of the old situation where the filesystem names were all created statically in the dentry tree, rather than being looked up dynamically based on the eventfs data structures.

You could see it in the naming - how it claimed to "create" dentries rather than just look up the dentries that were given it.

You could see it in various nonsensical and very incorrect operations, like using "simple_lookup()" on the dentries that were passed in, which only results in those dentries becoming negative dentries. Which meant that any other lookup would possibly return ENOENT if it saw that negative dentry before the data was then later filled in.

You could see it in the immense amount of nonsensical code that didn't actually just do lookups.

Link: https://lore.kernel.org/linux-trace-kernel/202401291043.e62e89dc-oliver.sang... Link: https://lore.kernel.org/linux-trace-kernel/20240131233227.73db55e1@gandalf.l...

Cc: stable@vger.kernel.org Cc: Al Viro viro@ZenIV.linux.org.uk Cc: Masami Hiramatsu mhiramat@kernel.org Cc: Mathieu Desnoyers mathieu.desnoyers@efficios.com Cc: Christian Brauner brauner@kernel.org Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: Ajay Kaher ajay.kaher@broadcom.com Cc: Mark Rutland mark.rutland@arm.com Fixes: c1504e510238 ("eventfs: Implement eventfs dir creation functions") Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org (cherry picked from commit 49304c2b93e4f7468b51ef717cbe637981397115) --- fs/tracefs/event_inode.c | 275 +++++++-------------------------------- fs/tracefs/inode.c | 69 ---------- fs/tracefs/internal.h | 3 - 3 files changed, 50 insertions(+), 297 deletions(-)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c index e9819d719d2a..04c2ab90f93e 100644 --- a/fs/tracefs/event_inode.c +++ b/fs/tracefs/event_inode.c @@ -230,7 +230,6 @@ static struct eventfs_inode *eventfs_find_events(struct dentry *dentry) { struct eventfs_inode *ei;

- mutex_lock(&eventfs_mutex); do { // The parent is stable because we do not do renames dentry = dentry->d_parent; @@ -247,7 +246,6 @@ static struct eventfs_inode *eventfs_find_events(struct dentry *dentry) } // Walk upwards until you find the events inode } while (!ei->is_events); - mutex_unlock(&eventfs_mutex);

update_top_events_attr(ei, dentry->d_sb);

@@ -280,11 +278,10 @@ static void update_inode_attr(struct dentry *dentry, struct inode *inode, }

/** - * create_file - create a file in the tracefs filesystem - * @name: the name of the file to create. + * lookup_file - look up a file in the tracefs filesystem + * @dentry: the dentry to look up * @mode: the permission that the file should have. * @attr: saved attributes changed by user - * @parent: parent dentry for this file. * @data: something that the caller will want to get to later on. * @fop: struct file_operations that should be used for this file. * @@ -292,13 +289,13 @@ static void update_inode_attr(struct dentry *dentry, struct inode *inode, * directory. The inode.i_private pointer will point to @data in the open() * call. */ -static struct dentry *create_file(const char *name, umode_t mode, +static struct dentry *lookup_file(struct dentry *dentry, + umode_t mode, struct eventfs_attr *attr, - struct dentry *parent, void *data, + void *data, const struct file_operations *fop) { struct tracefs_inode *ti; - struct dentry *dentry; struct inode *inode;

if (!(mode & S_IFMT)) @@ -307,15 +304,9 @@ static struct dentry *create_file(const char *name, umode_t mode, if (WARN_ON_ONCE(!S_ISREG(mode))) return NULL;

- WARN_ON_ONCE(!parent); - 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); + return ERR_PTR(-ENOMEM);

/* If the user updated the directory's attributes, use them */ update_inode_attr(dentry, inode, attr, mode); @@ -329,32 +320,29 @@ static struct dentry *create_file(const char *name, umode_t mode,

ti = get_tracefs(inode); ti->flags |= TRACEFS_EVENT_INODE; - d_instantiate(dentry, inode); + + d_add(dentry, inode); fsnotify_create(dentry->d_parent->d_inode, dentry); - return eventfs_end_creating(dentry); + return dentry; };

/** - * create_dir - create a dir in the tracefs filesystem + * lookup_dir_entry - look up a dir in the tracefs filesystem + * @dentry: the directory to look up * @ei: the eventfs_inode that represents the directory to create - * @parent: parent dentry for this file. * - * This function will create a dentry for a directory represented by + * This function will look up a dentry for a directory represented by * a eventfs_inode. */ -static struct dentry *create_dir(struct eventfs_inode *ei, struct dentry *parent) +static struct dentry *lookup_dir_entry(struct dentry *dentry, + struct eventfs_inode *pei, struct eventfs_inode *ei) { struct tracefs_inode *ti; - struct dentry *dentry; struct inode *inode;

- dentry = eventfs_start_creating(ei->name, parent); - if (IS_ERR(dentry)) - return dentry; - inode = tracefs_get_inode(dentry->d_sb); if (unlikely(!inode)) - return eventfs_failed_creating(dentry); + return ERR_PTR(-ENOMEM);

/* If the user updated the directory's attributes, use them */ update_inode_attr(dentry, inode, &ei->attr, @@ -371,11 +359,14 @@ static struct dentry *create_dir(struct eventfs_inode *ei, struct dentry *parent /* Only directories have ti->private set to an ei, not files */ ti->private = ei;

+ dentry->d_fsdata = ei; + ei->dentry = dentry; // Remove me! + inc_nlink(inode); - d_instantiate(dentry, inode); + d_add(dentry, inode); inc_nlink(dentry->d_parent->d_inode); fsnotify_mkdir(dentry->d_parent->d_inode, dentry); - return eventfs_end_creating(dentry); + return dentry; }

static void free_ei(struct eventfs_inode *ei) @@ -425,7 +416,7 @@ void eventfs_set_ei_status_free(struct tracefs_inode *ti, struct dentry *dentry) }

/** - * create_file_dentry - create a dentry for a file of an eventfs_inode + * lookup_file_dentry - create a dentry for a file of an eventfs_inode * @ei: the eventfs_inode that the file will be created under * @idx: the index into the d_children[] of the @ei * @parent: The parent dentry of the created file. @@ -438,157 +429,21 @@ void eventfs_set_ei_status_free(struct tracefs_inode *ti, struct dentry *dentry) * address located at @e_dentry. */ static struct dentry * -create_file_dentry(struct eventfs_inode *ei, int idx, - struct dentry *parent, const char *name, umode_t mode, void *data, +lookup_file_dentry(struct dentry *dentry, + struct eventfs_inode *ei, int idx, + umode_t mode, void *data, const struct file_operations *fops) { struct eventfs_attr *attr = NULL; struct dentry **e_dentry = &ei->d_children[idx]; - struct dentry *dentry; - - WARN_ON_ONCE(!inode_is_locked(parent->d_inode));

- mutex_lock(&eventfs_mutex); - if (ei->is_freed) { - mutex_unlock(&eventfs_mutex); - return NULL; - } - /* If the e_dentry already has a dentry, use it */ - if (*e_dentry) { - dget(*e_dentry); - mutex_unlock(&eventfs_mutex); - return *e_dentry; - } - - /* ei->entry_attrs are protected by SRCU */ if (ei->entry_attrs) attr = &ei->entry_attrs[idx];

- mutex_unlock(&eventfs_mutex); - - dentry = create_file(name, mode, attr, parent, data, fops); + dentry->d_fsdata = ei; // NOTE: ei of _parent_ + lookup_file(dentry, mode, attr, data, fops);

- mutex_lock(&eventfs_mutex); - - if (IS_ERR_OR_NULL(dentry)) { - /* - * When the mutex was released, something else could have - * created the dentry for this e_dentry. In which case - * use that one. - * - * If ei->is_freed is set, the e_dentry is currently on its - * way to being freed, don't return it. If e_dentry is NULL - * it means it was already freed. - */ - if (ei->is_freed) { - dentry = NULL; - } else { - dentry = *e_dentry; - dget(dentry); - } - mutex_unlock(&eventfs_mutex); - return dentry; - } - - if (!*e_dentry && !ei->is_freed) { - *e_dentry = dentry; - dentry->d_fsdata = ei; - } else { - /* - * Should never happen unless we get here due to being freed. - * Otherwise it means two dentries exist with the same name. - */ - WARN_ON_ONCE(!ei->is_freed); - dentry = NULL; - } - mutex_unlock(&eventfs_mutex); - - return dentry; -} - -/** - * eventfs_post_create_dir - post create dir routine - * @ei: eventfs_inode of recently created dir - * - * Map the meta-data of files within an eventfs dir to their parent dentry - */ -static void eventfs_post_create_dir(struct eventfs_inode *ei) -{ - struct eventfs_inode *ei_child; - - lockdep_assert_held(&eventfs_mutex); - - /* srcu lock already held */ - /* fill parent-child relation */ - list_for_each_entry_srcu(ei_child, &ei->children, list, - srcu_read_lock_held(&eventfs_srcu)) { - ei_child->d_parent = ei->dentry; - } -} - -/** - * create_dir_dentry - Create a directory dentry for the eventfs_inode - * @pei: The eventfs_inode parent of ei. - * @ei: The eventfs_inode to create the directory for - * @parent: The dentry of the parent of this directory - * - * This creates and attaches a directory dentry to the eventfs_inode @ei. - */ -static struct dentry * -create_dir_dentry(struct eventfs_inode *pei, struct eventfs_inode *ei, - struct dentry *parent) -{ - struct dentry *dentry = NULL; - - WARN_ON_ONCE(!inode_is_locked(parent->d_inode)); - - mutex_lock(&eventfs_mutex); - if (pei->is_freed || ei->is_freed) { - mutex_unlock(&eventfs_mutex); - return NULL; - } - if (ei->dentry) { - /* If the eventfs_inode already has a dentry, use it */ - dentry = ei->dentry; - dget(dentry); - mutex_unlock(&eventfs_mutex); - return dentry; - } - mutex_unlock(&eventfs_mutex); - - dentry = create_dir(ei, parent); - - mutex_lock(&eventfs_mutex); - - if (IS_ERR_OR_NULL(dentry) && !ei->is_freed) { - /* - * When the mutex was released, something else could have - * created the dentry for this e_dentry. In which case - * use that one. - * - * If ei->is_freed is set, the e_dentry is currently on its - * way to being freed. - */ - dentry = ei->dentry; - if (dentry) - dget(dentry); - mutex_unlock(&eventfs_mutex); - return dentry; - } - - if (!ei->dentry && !ei->is_freed) { - ei->dentry = dentry; - eventfs_post_create_dir(ei); - dentry->d_fsdata = ei; - } else { - /* - * Should never happen unless we get here due to being freed. - * Otherwise it means two dentries exist with the same name. - */ - WARN_ON_ONCE(!ei->is_freed); - dentry = NULL; - } - mutex_unlock(&eventfs_mutex); + *e_dentry = dentry; // Remove me

return dentry; } @@ -607,79 +462,49 @@ static struct dentry *eventfs_root_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags) { - const struct file_operations *fops; - const struct eventfs_entry *entry; struct eventfs_inode *ei_child; struct tracefs_inode *ti; struct eventfs_inode *ei; - struct dentry *ei_dentry = NULL; - struct dentry *ret = NULL; - struct dentry *d; const char *name = dentry->d_name.name; - umode_t mode; - void *data; - int idx; - int i; - int r;

ti = get_tracefs(dir); if (!(ti->flags & TRACEFS_EVENT_INODE)) - return NULL; - - /* Grab srcu to prevent the ei from going away */ - idx = srcu_read_lock(&eventfs_srcu); + return ERR_PTR(-EIO);

- /* - * Grab the eventfs_mutex to consistent value from ti->private. - * This s - */ mutex_lock(&eventfs_mutex); - ei = READ_ONCE(ti->private); - if (ei && !ei->is_freed) - ei_dentry = READ_ONCE(ei->dentry); - mutex_unlock(&eventfs_mutex);

- if (!ei || !ei_dentry) + ei = ti->private; + if (!ei || ei->is_freed) goto out;

- data = ei->data; - - list_for_each_entry_srcu(ei_child, &ei->children, list, - srcu_read_lock_held(&eventfs_srcu)) { + list_for_each_entry(ei_child, &ei->children, list) { if (strcmp(ei_child->name, name) != 0) continue; - ret = simple_lookup(dir, dentry, flags); - if (IS_ERR(ret)) + if (ei_child->is_freed) goto out; - d = create_dir_dentry(ei, ei_child, ei_dentry); - dput(d); + lookup_dir_entry(dentry, ei, ei_child); goto out; }

- for (i = 0; i < ei->nr_entries; i++) { - entry = &ei->entries[i]; - if (strcmp(name, entry->name) == 0) { - void *cdata = data; - mutex_lock(&eventfs_mutex); - /* If ei->is_freed, then the event itself may be too */ - if (!ei->is_freed) - r = entry->callback(name, &mode, &cdata, &fops); - else - r = -1; - mutex_unlock(&eventfs_mutex); - if (r <= 0) - continue; - ret = simple_lookup(dir, dentry, flags); - if (IS_ERR(ret)) - goto out; - d = create_file_dentry(ei, i, ei_dentry, name, mode, cdata, fops); - dput(d); - break; - } + for (int i = 0; i < ei->nr_entries; i++) { + void *data; + umode_t mode; + const struct file_operations *fops; + const struct eventfs_entry *entry = &ei->entries[i]; + + if (strcmp(name, entry->name) != 0) + continue; + + data = ei->data; + if (entry->callback(name, &mode, &data, &fops) <= 0) + goto out; + + lookup_file_dentry(dentry, ei, i, mode, data, fops); + goto out; } out: - srcu_read_unlock(&eventfs_srcu, idx); - return ret; + mutex_unlock(&eventfs_mutex); + return NULL; }

/* diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c index 888e42087847..5c84460feeeb 100644 --- a/fs/tracefs/inode.c +++ b/fs/tracefs/inode.c @@ -495,75 +495,6 @@ 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; - - /* Must always have a parent. */ - if (WARN_ON_ONCE(!parent)) - return ERR_PTR(-EINVAL); - - error = simple_pin_fs(&trace_fs_type, &tracefs_mount, - &tracefs_mount_count); - if (error) - return ERR_PTR(error); - - 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; -} - /* Find the inode that this will use for default */ static struct inode *instance_inode(struct dentry *parent, struct inode *inode) { diff --git a/fs/tracefs/internal.h b/fs/tracefs/internal.h index 7d84349ade87..09037e2c173d 100644 --- a/fs/tracefs/internal.h +++ b/fs/tracefs/internal.h @@ -80,9 +80,6 @@ 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_ei_status_free(struct tracefs_inode *ti, struct dentry *dentry);

#endif /* _TRACEFS_INTERNAL_H */

From: Linus Torvalds torvalds@linux-foundation.org

In order for the dentries to stay up-to-date with the eventfs changes, just add a 'd_revalidate' function that checks the 'is_freed' bit.

Also, clean up the dentry release to actually use d_release() rather than the slightly odd d_iput() function. We don't care about the inode, all we want to do is to get rid of the refcount to the eventfs data added by dentry->d_fsdata.

It would probably be cleaner to make eventfs its own filesystem, or at least set its own dentry ops when looking up eventfs files. But as it is, only eventfs dentries use d_fsdata, so we don't really need to split these things up by use.

Another thing that might be worth doing is to make all eventfs lookups mark their dentries as not worth caching. We could do that with d_delete(), but the DCACHE_DONTCACHE flag would likely be even better.

As it is, the dentries are all freeable, but they only tend to get freed at memory pressure rather than more proactively. But that's a separate issue.

Link: https://lore.kernel.org/linux-trace-kernel/202401291043.e62e89dc-oliver.sang... Link: https://lore.kernel.org/linux-trace-kernel/20240131185513.124644253@goodmis....

Cc: stable@vger.kernel.org Cc: Masami Hiramatsu mhiramat@kernel.org Cc: Mark Rutland mark.rutland@arm.com Cc: Mathieu Desnoyers mathieu.desnoyers@efficios.com Cc: Christian Brauner brauner@kernel.org Cc: Al Viro viro@ZenIV.linux.org.uk Cc: Ajay Kaher ajay.kaher@broadcom.com Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Fixes: c1504e510238 ("eventfs: Implement eventfs dir creation functions") Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org (cherry picked from commit 8dce06e98c70a7fcbb4bca7d90faf40522e65c58) --- fs/tracefs/event_inode.c | 5 ++--- fs/tracefs/inode.c | 27 ++++++++++++++++++--------- fs/tracefs/internal.h | 3 ++- 3 files changed, 22 insertions(+), 13 deletions(-)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c index 16ca8d9759b1..b2285d5f3fed 100644 --- a/fs/tracefs/event_inode.c +++ b/fs/tracefs/event_inode.c @@ -378,13 +378,12 @@ static void free_ei(struct eventfs_inode *ei) }

/** - * eventfs_set_ei_status_free - remove the dentry reference from an eventfs_inode - * @ti: the tracefs_inode of the dentry + * eventfs_d_release - dentry is going away * @dentry: dentry which has the reference to remove. * * Remove the association between a dentry from an eventfs_inode. */ -void eventfs_set_ei_status_free(struct tracefs_inode *ti, struct dentry *dentry) +void eventfs_d_release(struct dentry *dentry) { struct eventfs_inode *ei; int i; diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c index 5c84460feeeb..d65ffad4c327 100644 --- a/fs/tracefs/inode.c +++ b/fs/tracefs/inode.c @@ -377,21 +377,30 @@ static const struct super_operations tracefs_super_operations = { .show_options = tracefs_show_options, };

-static void tracefs_dentry_iput(struct dentry *dentry, struct inode *inode) +/* + * It would be cleaner if eventfs had its own dentry ops. + * + * Note that d_revalidate is called potentially under RCU, + * so it can't take the eventfs mutex etc. It's fine - if + * we open a file just as it's marked dead, things will + * still work just fine, and just see the old stale case. + */ +static void tracefs_d_release(struct dentry *dentry) { - struct tracefs_inode *ti; + if (dentry->d_fsdata) + eventfs_d_release(dentry); +}

- if (!dentry || !inode) - return; +static int tracefs_d_revalidate(struct dentry *dentry, unsigned int flags) +{ + struct eventfs_inode *ei = dentry->d_fsdata;

- ti = get_tracefs(inode); - if (ti && ti->flags & TRACEFS_EVENT_INODE) - eventfs_set_ei_status_free(ti, dentry); - iput(inode); + return !(ei && ei->is_freed); }

static const struct dentry_operations tracefs_dentry_operations = { - .d_iput = tracefs_dentry_iput, + .d_revalidate = tracefs_d_revalidate, + .d_release = tracefs_d_release, };

static int trace_fill_super(struct super_block *sb, void *data, int silent) diff --git a/fs/tracefs/internal.h b/fs/tracefs/internal.h index 932733a2696a..4b50a0668055 100644 --- a/fs/tracefs/internal.h +++ b/fs/tracefs/internal.h @@ -78,6 +78,7 @@ 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); -void eventfs_set_ei_status_free(struct tracefs_inode *ti, struct dentry *dentry); + +void eventfs_d_release(struct dentry *dentry);

#endif /* _TRACEFS_INTERNAL_H */

From: "Steven Rostedt (Google)" rostedt@goodmis.org

There should never be a case where an evenfs_inode is being freed without is_freed being set. Add a WARN_ON_ONCE() if it ever happens. That would mean there was one too many put_ei()s.

Link: https://lore.kernel.org/linux-trace-kernel/20240201161616.843551963@goodmis....

Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Masami Hiramatsu mhiramat@kernel.org Cc: Mark Rutland mark.rutland@arm.com Cc: Mathieu Desnoyers mathieu.desnoyers@efficios.com Cc: Christian Brauner brauner@kernel.org Cc: Al Viro viro@ZenIV.linux.org.uk Cc: Ajay Kaher ajay.kaher@broadcom.com Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org (cherry picked from commit 5a49f996046ba947466bc7461e4b19c4d1daf978) --- fs/tracefs/event_inode.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c index 515fdace1eea..ca7daee7c811 100644 --- a/fs/tracefs/event_inode.c +++ b/fs/tracefs/event_inode.c @@ -73,6 +73,9 @@ enum { static void release_ei(struct kref *ref) { struct eventfs_inode *ei = container_of(ref, struct eventfs_inode, kref); + + WARN_ON_ONCE(!ei->is_freed); + kfree(ei->entry_attrs); kfree_const(ei->name); kfree_rcu(ei, rcu); @@ -84,6 +87,14 @@ static inline void put_ei(struct eventfs_inode *ei) kref_put(&ei->kref, release_ei); }

+static inline void free_ei(struct eventfs_inode *ei) +{ + if (ei) { + ei->is_freed = 1; + put_ei(ei); + } +} + static inline struct eventfs_inode *get_ei(struct eventfs_inode *ei) { if (ei) @@ -679,7 +690,7 @@ struct eventfs_inode *eventfs_create_dir(const char *name, struct eventfs_inode

/* Was the parent freed? */ if (list_empty(&ei->list)) { - put_ei(ei); + free_ei(ei); ei = NULL; } return ei; @@ -770,7 +781,7 @@ struct eventfs_inode *eventfs_create_events_dir(const char *name, struct dentry return ei;

fail: - put_ei(ei); + free_ei(ei); tracefs_failed_creating(dentry); return ERR_PTR(-ENOMEM); } @@ -801,9 +812,8 @@ static void eventfs_remove_rec(struct eventfs_inode *ei, int level) list_for_each_entry(ei_child, &ei->children, list) eventfs_remove_rec(ei_child, level + 1);

- ei->is_freed = 1; list_del(&ei->list); - put_ei(ei); + free_ei(ei); }

/**

From: "Steven Rostedt (Google)" rostedt@goodmis.org

The dentries and inodes are created when referenced in the lookup code. There's no reason to call fsnotify_*() functions when they are created by a reference. It doesn't make any sense.

Link: https://lore.kernel.org/linux-trace-kernel/20240201002719.GS2087318@ZenIV/ Link: https://lore.kernel.org/linux-trace-kernel/20240201161617.166973329@goodmis....

Cc: stable@vger.kernel.org Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Masami Hiramatsu mhiramat@kernel.org Cc: Mark Rutland mark.rutland@arm.com Cc: Mathieu Desnoyers mathieu.desnoyers@efficios.com Cc: Christian Brauner brauner@kernel.org Cc: Al Viro viro@ZenIV.linux.org.uk Cc: Ajay Kaher ajay.kaher@broadcom.com Fixes: a376007917776 ("eventfs: Implement functions to create files and dirs when accessed"); Suggested-by: Al Viro viro@zeniv.linux.org.uk Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org (cherry picked from commit 12d823b31fadf47c8f36ecada7abac5f903cac33) --- fs/tracefs/event_inode.c | 2 -- 1 file changed, 2 deletions(-)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c index ca7daee7c811..9e031e5a2713 100644 --- a/fs/tracefs/event_inode.c +++ b/fs/tracefs/event_inode.c @@ -366,7 +366,6 @@ static struct dentry *lookup_file(struct eventfs_inode *parent_ei, dentry->d_fsdata = get_ei(parent_ei);

d_add(dentry, inode); - fsnotify_create(dentry->d_parent->d_inode, dentry); return NULL; };

@@ -408,7 +407,6 @@ static struct dentry *lookup_dir_entry(struct dentry *dentry, inc_nlink(inode); d_add(dentry, inode); inc_nlink(dentry->d_parent->d_inode); - fsnotify_mkdir(dentry->d_parent->d_inode, dentry); return NULL; }