On Mon, Apr 26, 2021 at 9:42 PM Gabriel Krisman Bertazi
<krisman@xxxxxxxxxxxxx> wrote:
>
> Expose a new type of fsnotify event for filesystems to report errors for
> userspace monitoring tools. fanotify will send this type of
> notification for FAN_ERROR marks.
>
> Signed-off-by: Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxx>
> ---
> fs/notify/fsnotify.c | 2 +-
> include/linux/fsnotify_backend.h | 16 ++++++++++++++++
> 2 files changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
> index 30d422b8c0fc..9fff35e67b37 100644
> --- a/fs/notify/fsnotify.c
> +++ b/fs/notify/fsnotify.c
> @@ -558,7 +558,7 @@ static __init int fsnotify_init(void)
> {
> int ret;
>
> - BUILD_BUG_ON(HWEIGHT32(ALL_FSNOTIFY_BITS) != 25);
> + BUILD_BUG_ON(HWEIGHT32(ALL_FSNOTIFY_BITS) != 26);
>
> ret = init_srcu_struct(&fsnotify_mark_srcu);
> if (ret)
> diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
> index a1a4dd69e5ed..f850bfbe30d4 100644
> --- a/include/linux/fsnotify_backend.h
> +++ b/include/linux/fsnotify_backend.h
> @@ -48,6 +48,8 @@
> #define FS_ACCESS_PERM 0x00020000 /* access event in a permissions hook */
> #define FS_OPEN_EXEC_PERM 0x00040000 /* open/exec event in a permission hook */
>
> +#define FS_ERROR 0x00100000 /* Used for filesystem error reporting */
> +
Why skip 0x00080000?
Anyway, event bits are starting to run out so I would prefer that you overload
an existing bit used only by inotify/dnotify.
FS_IN_IGNORED is completely internal to inotify and there is no need to
set it in i_fsnotify_mask at all, so if we remove the bit from the output of
inotify_arg_to_mask() no functionality will change and we will be able to
overload the event bit for FS_ERROR (see patch below).
I also kind of like that FS_ERROR is adjacent to FS_UMOUNT and
FS_Q_OVERFLOW :-)
Other FS_IN/FS_DN bits may also be reclaimed but it takes a bit more work
I have patches for those.
Thanks,
Amir.
diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c
index 98f61b31745a..351517bae716 100644
--- a/fs/notify/inotify/inotify_user.c
+++ b/fs/notify/inotify/inotify_user.c
@@ -89,10 +89,10 @@ static inline __u32 inotify_arg_to_mask(struct
inode *inode, u32 arg)
__u32 mask;
/*
- * Everything should accept their own ignored and should receive events
- * when the inode is unmounted. All directories care about children.
+ * Everything should receive events when the inode is unmounted.
+ * All directories care about children.
*/
- mask = (FS_IN_IGNORED | FS_UNMOUNT);
+ mask = FS_UNMOUNT;
if (S_ISDIR(inode->i_mode))
mask |= FS_EVENT_ON_CHILD;
diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index 1ce66748a2d2..ecbafb3f36d7 100644
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -42,6 +42,11 @@
#define FS_UNMOUNT 0x00002000 /* inode on umount fs */
#define FS_Q_OVERFLOW 0x00004000 /* Event queued overflowed */
+#define FS_ERROR 0x00008000 /* Filesystem error report */
+/*
+ * FS_IN_IGNORED overloads FS_ERROR. It is only used internally by inotify
+ * which does not support FS_ERROR.
+ */
#define FS_IN_IGNORED 0x00008000 /* last inotify event here */
