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References: <20211019000015.1666608-1-krisman@collabora.com> <20211019000015.1666608-23-krisman@collabora.com>
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From:   Amir Goldstein <amir73il@gmail.com>
Date:   Tue, 19 Oct 2021 08:56:32 +0300
Message-ID: <CAOQ4uxi2D_X1TwajwEUuKz8AzeWyphQTAMZ1S=zioQkLPkUcMA@mail.gmail.com>
Subject: Re: [PATCH v8 22/32] fanotify: Support merging of error events
To:     Gabriel Krisman Bertazi <krisman@collabora.com>
Cc:     Jan Kara <jack@suse.com>, "Darrick J. Wong" <djwong@kernel.org>,
        Theodore Tso <tytso@mit.edu>,
        Dave Chinner <david@fromorbit.com>,
        David Howells <dhowells@redhat.com>,
        Khazhismel Kumykov <khazhy@google.com>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Ext4 <linux-ext4@vger.kernel.org>,
        Linux API <linux-api@vger.kernel.org>, kernel@collabora.com
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On Tue, Oct 19, 2021 at 3:03 AM Gabriel Krisman Bertazi
<krisman@collabora.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@collabora.com>
>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>

> ---
> Changes since v7:
>   - Move fee->fsid assignment here (Amir)
>   - Open code error event merge logic in fanotify_merge (Jan)
> ---
>  fs/notify/fanotify/fanotify.c | 26 ++++++++++++++++++++++++--
>  fs/notify/fanotify/fanotify.h |  4 +++-
>  2 files changed, 27 insertions(+), 3 deletions(-)
>
> diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
> index 1f195c95dfcd..cedcb1546804 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);
>         }
> @@ -176,6 +189,10 @@ static int fanotify_merge(struct fsnotify_group *group,
>                         break;
>                 if (fanotify_should_merge(old, new)) {
>                         old->mask |= new->mask;
> +
> +                       if (fanotify_is_error_event(old->mask))
> +                               FANOTIFY_EE(old)->err_count++;
> +
>                         return 1;
>                 }
>         }
> @@ -577,7 +594,8 @@ 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 +609,10 @@ static struct fanotify_event *fanotify_alloc_error_event(
>                 return NULL;
>
>         fee->fae.type = FANOTIFY_EVENT_TYPE_FS_ERROR;
> +       fee->err_count = 1;
> +       fee->fsid = *fsid;
> +
> +       *hash ^= fanotify_hash_fsid(fsid);
>
>         return &fee->fae;
>  }
> @@ -664,7 +686,7 @@ static struct fanotify_event *fanotify_alloc_event(struct fsnotify_group *group,
>                 event = fanotify_alloc_perm_event(path, gfp);
>         } else if (fanotify_is_error_event(mask)) {
>                 event = fanotify_alloc_error_event(group, fsid, data,
> -                                                  data_type);
> +                                                  data_type, &hash);
>         } else if (name_event && (file_name || child)) {
>                 event = fanotify_alloc_name_event(id, fsid, file_name, child,
>                                                   &hash, gfp);
> diff --git a/fs/notify/fanotify/fanotify.h b/fs/notify/fanotify/fanotify.h
> index ebef952481fa..2b032b79d5b0 100644
> --- a/fs/notify/fanotify/fanotify.h
> +++ b/fs/notify/fanotify/fanotify.h
> @@ -199,6 +199,9 @@ FANOTIFY_NE(struct fanotify_event *event)
>
>  struct fanotify_error_event {
>         struct fanotify_event fae;
> +       u32 err_count; /* Suppressed errors count */
> +
> +       __kernel_fsid_t fsid; /* FSID this error refers to. */
>  };
>
>  static inline struct fanotify_error_event *
> @@ -332,7 +335,6 @@ static inline struct path *fanotify_event_path(struct fanotify_event *event)
>  static inline bool fanotify_is_hashed_event(u32 mask)
>  {
>         return !(fanotify_is_perm_event(mask) ||
> -                fanotify_is_error_event(mask) ||
>                  fsnotify_is_overflow_event(mask));
>  }
>
> --
> 2.33.0
>