linux-ext4 - Re: [PATCH v7 21/28] fanotify: Support merging of error events

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Date:   Fri, 15 Oct 2021 10:09:36 +0300
From:   Amir Goldstein <amir73il@...il.com>
To:     Gabriel Krisman Bertazi <krisman@...labora.com>
Cc:     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 21/28] fanotify: Support merging of error events

On Fri, Oct 15, 2021 at 12:39 AM Gabriel Krisman Bertazi
<krisman@...labora.com> wrote:
>
> Error events (FAN_FS_ERROR) against the same file system can be merged
> by simply iterating the error count.  The hash is taken from the fsid,
> without considering the FH.  This means that only the first error object
> is reported.
>
> Signed-off-by: Gabriel Krisman Bertazi <krisman@...labora.com>
> ---
>  fs/notify/fanotify/fanotify.c | 39 ++++++++++++++++++++++++++++++++---
>  fs/notify/fanotify/fanotify.h |  4 +++-
>  2 files changed, 39 insertions(+), 4 deletions(-)
>
> diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
> index 9b970359570a..7032083df62a 100644
> --- a/fs/notify/fanotify/fanotify.c
> +++ b/fs/notify/fanotify/fanotify.c
> @@ -111,6 +111,16 @@ static bool fanotify_name_event_equal(struct fanotify_name_event *fne1,
>         return fanotify_info_equal(info1, info2);
>  }
>
> +static bool fanotify_error_event_equal(struct fanotify_error_event *fee1,
> +                                      struct fanotify_error_event *fee2)
> +{
> +       /* Error events against the same file system are always merged. */
> +       if (!fanotify_fsid_equal(&fee1->fsid, &fee2->fsid))
> +               return false;
> +
> +       return true;
> +}
> +
>  static bool fanotify_should_merge(struct fanotify_event *old,
>                                   struct fanotify_event *new)
>  {
> @@ -141,6 +151,9 @@ static bool fanotify_should_merge(struct fanotify_event *old,
>         case FANOTIFY_EVENT_TYPE_FID_NAME:
>                 return fanotify_name_event_equal(FANOTIFY_NE(old),
>                                                  FANOTIFY_NE(new));
> +       case FANOTIFY_EVENT_TYPE_FS_ERROR:
> +               return fanotify_error_event_equal(FANOTIFY_EE(old),
> +                                                 FANOTIFY_EE(new));
>         default:
>                 WARN_ON_ONCE(1);
>         }
> @@ -148,6 +161,22 @@ static bool fanotify_should_merge(struct fanotify_event *old,
>         return false;
>  }
>
> +static void fanotify_merge_error_event(struct fanotify_error_event *dest,
> +                                      struct fanotify_error_event *origin)
> +{
> +       dest->err_count++;
> +}
> +
> +static void fanotify_merge_event(struct fanotify_event *dest,
> +                                struct fanotify_event *origin)
> +{
> +       dest->mask |= origin->mask;
> +
> +       if (origin->type == FANOTIFY_EVENT_TYPE_FS_ERROR)
> +               fanotify_merge_error_event(FANOTIFY_EE(dest),
> +                                          FANOTIFY_EE(origin));
> +}
> +
>  /* Limit event merges to limit CPU overhead per event */
>  #define FANOTIFY_MAX_MERGE_EVENTS 128
>
> @@ -175,7 +204,7 @@ static int fanotify_merge(struct fsnotify_group *group,
>                 if (++i > FANOTIFY_MAX_MERGE_EVENTS)
>                         break;
>                 if (fanotify_should_merge(old, new)) {
> -                       old->mask |= new->mask;
> +                       fanotify_merge_event(old, new);
>                         return 1;
>                 }
>         }
> @@ -577,7 +606,8 @@ static struct fanotify_event *fanotify_alloc_name_event(struct inode *id,
>  static struct fanotify_event *fanotify_alloc_error_event(
>                                                 struct fsnotify_group *group,
>                                                 __kernel_fsid_t *fsid,
> -                                               const void *data, int data_type)
> +                                               const void *data, int data_type,
> +                                               unsigned int *hash)
>  {
>         struct fs_error_report *report =
>                         fsnotify_data_error_report(data, data_type);
> @@ -591,6 +621,9 @@ static struct fanotify_event *fanotify_alloc_error_event(
>                 return NULL;
>
>         fee->fae.type = FANOTIFY_EVENT_TYPE_FS_ERROR;
> +       fee->err_count = 1;
> +
> +       *hash ^= fanotify_hash_fsid(fsid);
>
>         return &fee->fae;
>  }

Forgot to store fee->fsid?

Thanks,
Amir.