On Fri 15-10-21 10:56:38, Amir Goldstein wrote:
> On Fri, Oct 15, 2021 at 12:39 AM Gabriel Krisman Bertazi
> <krisman@xxxxxxxxxxxxx> wrote:
> >
> > Plumb the pieces to add a FID report to error records. Since all error
> > event memory must be pre-allocated, we pre-allocate the maximum file
> > handle size possible, such that it should always fit.
> >
> > For errors that don't expose a file handle report it with an invalid
> > FID.
> >
> > Signed-off-by: Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxx>
> >
> > ---
> > Changes since v6:
> > - pass fsid from handle_events
> > Changes since v5:
> > - Use preallocated MAX_HANDLE_SZ FH buffer
> > - Report superblock errors with a zerolength INVALID FID (jan, amir)
> > ---
> > fs/notify/fanotify/fanotify.c | 15 +++++++++++++++
> > fs/notify/fanotify/fanotify.h | 8 ++++++++
> > 2 files changed, 23 insertions(+)
> >
> > diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
> > index 7032083df62a..8a60c96f5fb2 100644
> > --- a/fs/notify/fanotify/fanotify.c
> > +++ b/fs/notify/fanotify/fanotify.c
> > @@ -611,7 +611,9 @@ static struct fanotify_event *fanotify_alloc_error_event(
> > {
> > struct fs_error_report *report =
> > fsnotify_data_error_report(data, data_type);
> > + struct inode *inode = report->inode;
> > struct fanotify_error_event *fee;
> > + int fh_len;
> >
> > if (WARN_ON(!report))
> > return NULL;
> > @@ -622,6 +624,19 @@ static struct fanotify_event *fanotify_alloc_error_event(
> >
> > fee->fae.type = FANOTIFY_EVENT_TYPE_FS_ERROR;
> > fee->err_count = 1;
> > + fee->fsid = *fsid;
> > +
> > + fh_len = fanotify_encode_fh_len(inode);
> > + if (WARN_ON(fh_len > MAX_HANDLE_SZ)) {
>
> WARN_ON_ONCE please and I rather that this sanity check is moved inside
> fanotify_encode_fh_len() where it will return 0 for encoding failure.
Yeah, that's better.
> > diff --git a/fs/notify/fanotify/fanotify.h b/fs/notify/fanotify/fanotify.h
> > index 2b032b79d5b0..b58400926f92 100644
> > --- a/fs/notify/fanotify/fanotify.h
> > +++ b/fs/notify/fanotify/fanotify.h
> > @@ -202,6 +202,10 @@ struct fanotify_error_event {
> > u32 err_count; /* Suppressed errors count */
> >
> > __kernel_fsid_t fsid; /* FSID this error refers to. */
> > + /* object_fh must be followed by the inline handle buffer. */
> > + struct fanotify_fh object_fh;
> > + /* Reserve space in object_fh.buf[] - access with fanotify_fh_buf() */
> > + unsigned char _inline_fh_buf[MAX_HANDLE_SZ];
> > };
>
> This struct duplicates most of struct fanotify_fid_event.
> How about:
>
> #define FANOTIFY_ERROR_FH_LEN \
> (MAX_HANDLE_SZ - FANOTIFY_INLINE_FH_LEN)
>
> struct fanotify_error_event {
> u32 err_count; /* Suppressed errors count */
> struct fanotify_event ffe;
> /* Reserve space in ffe.object_fh.buf[] - access with
> fanotify_fh_buf() */
> unsigned char _fh_buf[FANOTIFY_ERROR_FH_LEN];
> }
>
> Or leaving out the struct padding and passing
> FANOTIFY_ERROR_EVENT_SIZE as mempool object size?
>
> #define FANOTIFY_ERROR_EVENT_SIZE \
> (sizeof(struct fanotify_error_event) + FANOTIFY_ERROR_FH_LEN)
Hrm, I don't like either of these two options too much as IMHO it's rather
hard to understand what's going on. If we want to avoid the duplication,
then I see two relatively clean ways to do it:
a) Remove _inline_fh_buf from fanotify_fid_event (probably just leave a
comment there explaining how space is preallocated) and make sure kmem
cache for fanotify_fid_event has FANOTIFY_INLINE_FH_LEN in each object for
the fh, similarly error event would have MAX_HANDLE_SZ in the object.
b) Define a macro that expands to a struct definition with appropriate
buffer length.
I guess a) seems a bit more obvious to me but I can live with both...
Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
