Re: [linus:master] [eventfs] 852e46e239: BUG:unable_to_handle_page_fault_for_address
From: Steven Rostedt <rostedt@goodmis.org>
Date: 2024-01-30 17:06:23
Also in:
lkml, oe-lkp
Subsystem:
filesystems (vfs and infrastructure), the rest, tracing · Maintainers:
Alexander Viro, Christian Brauner, Linus Torvalds, Steven Rostedt, Masami Hiramatsu
On Tue, 30 Jan 2024 08:55:51 -0800 Linus Torvalds [off-list ref] wrote:
On Tue, 30 Jan 2024 at 08:49, Steven Rostedt [off-list ref] wrote:quoted
- On removal, I got rid of the SRCU callback and the work queue. Instead, I find the dentry of the current eventfs_inode that is being deleted by walking the ei->parent until I find the events inode that has a dentry. I then use that to do a lookup walking back down to the eventfs_inode I want to delete. This gives me the dentry that I can call d_invalidate() on.Yes, that works. However, I have a patch that is *much* smaller and simpler, and doesn't need that walk. The VFS layer already has a good interface for "should I still use this dentry", which is needed for various network filesystems etc that want to time out caches (or check explicitly whether the file still exists etc): it's the dentry d_revalidate() check. Let me just reboot into it to test that I got all the cases. It makes the code even more obvious, and avoids all the complexity.
I actually had this before, but it wasn't working (likely to something else that wasn't working or I did it wrong) so I reverted it. -- Steve
diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index 49d4630d5d70..9867b39ae24c 100644
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c@@ -451,6 +451,13 @@ lookup_file_dentry(struct dentry *dentry, return dentry; } +int eventfs_revalidate(struct dentry *dentry, unsigned int flags) +{ + struct eventfs_inode *ei = dentry->d_fsdata; + + return ei && !ei->is_freed; +} + /** * eventfs_root_lookup - lookup routine to create file/dir * @dir: in which a lookup is being done
diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
index e1b172c0e091..0395459d919e 100644
--- a/fs/tracefs/inode.c
+++ b/fs/tracefs/inode.c@@ -392,8 +392,24 @@ static void tracefs_dentry_iput(struct dentry *dentry, struct inode *inode) iput(inode); } +static int tracefs_revalidate(struct dentry *dentry, unsigned int flags) +{ + struct inode *inode = dentry->d_inode; + struct tracefs_inode *ti; + + if (!dentry || !inode) + return 0; + + ti = get_tracefs(inode); + if (!ti || !(ti->flags & TRACEFS_EVENT_INODE)) + return 1; + + return eventfs_revalidate(dentry, flags); +} + static const struct dentry_operations tracefs_dentry_operations = { - .d_iput = tracefs_dentry_iput, + .d_iput = tracefs_dentry_iput, + .d_revalidate = tracefs_revalidate, }; 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 2af78fd95c93..a1024202c4e5 100644
--- a/fs/tracefs/internal.h
+++ b/fs/tracefs/internal.h@@ -80,5 +80,6 @@ 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); +int eventfs_revalidate(struct dentry *dentry, unsigned int flags); #endif /* _TRACEFS_INTERNAL_H */