Re: [PATCH v7 23/28] fanotify: Report fid info for file related file system errors

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 <redacted>

---
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)) {

+               /*
+                * Fallback to reporting the error against the super
+                * block.  It should never happen.
+                */
+               inode = NULL;
+               fh_len = fanotify_encode_fh_len(NULL);
+       }
+
+       fanotify_encode_fh(&fee->object_fh, inode, fh_len, NULL, 0);

        *hash ^= fanotify_hash_fsid(fsid);

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];
 };