Re: [linus:master] [eventfs] 852e46e239: BUG:unable_to_handle_page_fault_for_address

Linus Torvalds
2024-01-29T20:52:21Z

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On Mon, 29 Jan 2024 at 12:25, Steven Rostedt <rostedt@goodmis.org> wrote:
>
> > So the fundamental bug I now find is that eventfs_root_lookup() gets a
> > target dentry, and for some unfathomable reason it then does
> >
> > ret = simple_lookup(dir, dentry, flags);
> >
> > on it. Which is *completely* broken, because what "simple_lookup()"
> > does is just say "oh, you didn't have a dentry of this kind before, so
> > clearly a lookup must be a non-existent file". Remember: this is for
> > 'tmpfs' kinds of filesystems where the dentry cache cotnains *ALL*
> > files.
>
> Sorry, I don't really understand what you mean by "ALL files"? You mean
> that all files in the pseudo file system has a dentry to it (like debugfs,
> and the rest of tracefs)?

Yes.

So the whole - and *ONLY* - point of 'simple_lookup()' is for
filesystems like tmpfs, or like debugfs or other filesystems like
that, which never actually *need* to look anything up, because
everything is already cached in the dentry tree.

That's what the "simple" part of the simple functions mean. They are
simple from a dcache standpoint, because the dcache is all there is.

End result: what simple_lookup() does is say "oh, you didn't have the
file, so it's by definition a negative dentry", and thus all it does
is to do "d_add(dentry, NULL)".

Anyway, removing this was painful. I initially thought "I'll just
remove the calls". But it all ended up cascading into "that's also
wrong".

So now I have a patch that tries to fix this all up, and it looks like thisL:

1 file changed, 50 insertions(+), 219 deletions(-)

because it basically removed all the old code, and replaced it with
much simpler code.

I'm including the patch here as an attachment, but I want to note very
clearly that this *builds* for me, and it looks a *lot* more obvious
and correct than the old code did, but I haven't tested it. AT ALL.

Also note that it depends on my previous patches, so I guess I'll
include them here again just to make it unambiguous.

Finally - this does *not* fix up the refcounting. I still think the
SRCU stuff is completely broken. But that's another headache. But at
least now the *lookup* parts look like they DTRT wrt eventfs_mutex.

The SRCU logic from the directory iteration parts still needs crapectomy.

AGAIN: these patches (ie particularly that last one - 0004) were all
done entirely "blindly" - I've looked at the code, and fixed the bugs
and problems I've seen by pure code inspection.

That's great, but it really means that it's all untested. It *looks*
better than the old code, but there may be some silly gotcha that I
have missed.

Linus

[-- Attachment #2: 0002-tracefs-avoid-using-the-ei-dentry-pointer-unnecessar.patch --]
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From b1f487acf6f4e9093d8b0fa00f864a6d07a3c4c2 Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Sat, 27 Jan 2024 13:27:01 -0800
Subject: [PATCH 2/4] tracefs: avoid using the ei->dentry pointer unnecessarily

The eventfs_find_events() code tries to walk up the tree to find the
event directory that a dentry belongs to, in order to then find the
eventfs inode that is associated with that event directory.

However, it uses an odd combination of walking the dentry parent,
looking up the eventfs inode associated with that, and then looking up
the dentry from there. Repeat.

But the code shouldn't have back-pointers to dentries in the first
place, and it should just walk the dentry parenthood chain directly.

Similarly, 'set_top_events_ownership()' looks up the dentry from the
eventfs inode, but the only reason it wants a dentry is to look up the
superblock in order to look up the root dentry.

But it already has the real filesystem inode, which has that same
superblock pointer. So just pass in the superblock pointer using the
information that's already there, instead of looking up extraneous data
that is irrelevant.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
fs/tracefs/event_inode.c | 26 ++++++++++++--------------
1 file changed, 12 insertions(+), 14 deletions(-)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index 1c3dd0ad4660..2d128bedd654 100644
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -156,33 +156,30 @@ 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)
+static void update_top_events_attr(struct eventfs_inode *ei, struct super_block *sb)
{
- struct inode *inode;
+ struct inode *root;

/* 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;
+ root = d_inode(sb->s_root);
+ ei->attr.uid = root->i_uid;
+ ei->attr.gid = root->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);
+ update_top_events_attr(ei, inode->i_sb);

if (!(ei->attr.mode & EVENTFS_SAVE_UID))
inode->i_uid = ei->attr.uid;
@@ -235,8 +232,10 @@ static struct eventfs_inode *eventfs_find_events(struct dentry *dentry)

mutex_lock(&eventfs_mutex);
do {
- /* The parent always has an ei, except for events itself */
- ei = dentry->d_parent->d_fsdata;
+ // The parent is stable because we do not do renames
+ dentry = dentry->d_parent;
+ // ... and directories always have d_fsdata
+ ei = dentry->d_fsdata;

/*
* If the ei is being freed, the ownership of the children
@@ -246,12 +245,11 @@ static struct eventfs_inode *eventfs_find_events(struct dentry *dentry)
ei = NULL;
break;
}
-
- dentry = ei->dentry;
+ // Walk upwards until you find the events inode
} while (!ei->is_events);
mutex_unlock(&eventfs_mutex);

- update_top_events_attr(ei, dentry);
+ update_top_events_attr(ei, dentry->d_sb);

return ei;
}
--
2.43.0.5.g38fb137bdb

[-- Attachment #3: 0003-eventfsfs-initialize-the-tracefs-inode-properly.patch --]
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From 6e5db10ebc96ebe6b9707c9938c450f51e9a3ae0 Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Mon, 29 Jan 2024 11:06:32 -0800
Subject: [PATCH 3/4] eventfsfs: initialize the tracefs inode properly

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

And the ->flags file was initialized incorrectly with a '|=', when the
old value was stale. It should have just been a straight assignment.

Move the field initializations up to before the d_instantiate, and fix
the use of uninitialized data.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
fs/tracefs/event_inode.c | 13 ++++++-------
1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index 2d128bedd654..c0d977e6c0f2 100644
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -328,7 +328,9 @@ static struct dentry *create_file(const char *name, umode_t mode,
inode->i_ino = EVENTFS_FILE_INODE_INO;

ti = get_tracefs(inode);
- ti->flags |= TRACEFS_EVENT_INODE;
+ ti->flags = TRACEFS_EVENT_INODE;
+ ti->private = NULL; // Directories have 'ei', files not
+
d_instantiate(dentry, inode);
fsnotify_create(dentry->d_parent->d_inode, dentry);
return eventfs_end_creating(dentry);
@@ -367,7 +369,8 @@ static struct dentry *create_dir(struct eventfs_inode *ei, struct dentry *parent
inode->i_ino = eventfs_dir_ino(ei);

ti = get_tracefs(inode);
- ti->flags |= TRACEFS_EVENT_INODE;
+ ti->flags = TRACEFS_EVENT_INODE;
+ ti->private = ei;

inc_nlink(inode);
d_instantiate(dentry, inode);
@@ -513,7 +516,6 @@ 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);

@@ -523,9 +525,6 @@ 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;
}

/**
@@ -943,7 +942,7 @@ struct eventfs_inode *eventfs_create_events_dir(const char *name, struct dentry
INIT_LIST_HEAD(&ei->list);

ti = get_tracefs(inode);
- ti->flags |= TRACEFS_EVENT_INODE | TRACEFS_EVENT_TOP_INODE;
+ ti->flags = TRACEFS_EVENT_INODE | TRACEFS_EVENT_TOP_INODE;
ti->private = ei;

inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
--
2.43.0.5.g38fb137bdb

[-- Attachment #4: 0001-tracefs-remove-stale-update_gid-code.patch --]
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From 41699c9c5830ca662badc3fa0d8cb59c491ce775 Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Sat, 27 Jan 2024 13:21:14 -0800
Subject: [PATCH 1/4] tracefs: remove stale 'update_gid' code

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

Fixes: 8186fff7ab64 ("tracefs/eventfs: Use root and instance inodes as default ownership")
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
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 */
--
2.43.0.5.g38fb137bdb

[-- Attachment #5: 0004-tracefs-dentry-lookup-crapectomy.patch --]
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From 9fe4f80dba499a1367f6563b205837efa54c9a93 Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Mon, 29 Jan 2024 12:25:53 -0800
Subject: [PATCH 4/4] tracefs: dentry lookup crapectomy

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 rwas then later filled in.

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

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
fs/tracefs/event_inode.c | 269 ++++++++-------------------------------
1 file changed, 50 insertions(+), 219 deletions(-)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index c0d977e6c0f2..cd6de3244442 100644
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -280,11 +280,10 @@ 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 +291,13 @@ 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))
@@ -307,12 +306,6 @@ 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);
@@ -337,23 +330,19 @@ static struct dentry *create_file(const char *name, umode_t mode,
};

/**
- * 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);
@@ -372,6 +361,9 @@ static struct dentry *create_dir(struct eventfs_inode *ei, struct dentry *parent
ti->flags = TRACEFS_EVENT_INODE;
ti->private = ei;

+ dentry->d_fsdata = ei;
+ ei->dentry = dentry; // Remove me!
+
inc_nlink(inode);
d_instantiate(dentry, inode);
inc_nlink(dentry->d_parent->d_inode);
@@ -426,7 +418,7 @@ 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.
@@ -439,157 +431,21 @@ 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->d_fsdata = ei; // NOTE: ei of _parent_
+ lookup_file(dentry, mode, attr, data, fops);

- dentry = create_file(name, mode, attr, parent, 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;
}
@@ -608,79 +464,54 @@ 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;
+ return ERR_PTR(-EIO);

- /* Grab srcu to prevent the ei from going away */
- idx = srcu_read_lock(&eventfs_srcu);
-
- /*
- * 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)
- goto out;
+ ei = ti->private;
+ if (!ei || ei->is_freed)
+ goto enoent;

- 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))
- goto out;
- d = create_dir_dentry(ei, ei_child, ei_dentry);
- dput(d);
+ if (ei_child->is_freed)
+ goto enoent;
+ 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 enoent;
+
+ lookup_file_dentry(dentry, ei, i, mode, data, fops);
+ goto out;
}
+
+ enoent:
+ /* Nothing found? */
+ d_add(dentry, NULL);
+
out:
- srcu_read_unlock(&eventfs_srcu, idx);
- return ret;
+ mutex_unlock(&eventfs_mutex);
+ return NULL;
}

/*
--
2.43.0.5.g38fb137bdb