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Date: Fri, 15 Oct 2021 15:38:11 +0200 From: Jan Kara <jack@...e.cz> To: Amir Goldstein <amir73il@...il.com> Cc: Gabriel Krisman Bertazi <krisman@...labora.com>, Jan Kara <jack@...e.com>, "Darrick J. Wong" <djwong@...nel.org>, Theodore Tso <tytso@....edu>, David Howells <dhowells@...hat.com>, Khazhismel Kumykov <khazhy@...gle.com>, linux-fsdevel <linux-fsdevel@...r.kernel.org>, Ext4 <linux-ext4@...r.kernel.org>, Linux API <linux-api@...r.kernel.org>, Matthew Bobrowski <repnop@...gle.com>, kernel@...labora.com Subject: Re: [PATCH v7 23/28] fanotify: Report fid info for file related file system errors On Fri 15-10-21 10:56:38, Amir Goldstein wrote: > On Fri, Oct 15, 2021 at 12:39 AM Gabriel Krisman Bertazi > <krisman@...labora.com> 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@...labora.com> > > > > --- > > 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@...e.com> SUSE Labs, CR
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