linux-ext4 - Re: [PATCH v8 22/32] fanotify: Support merging of error events

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Message-ID: <20211019135236.GK3255@quack2.suse.cz>
Date:   Tue, 19 Oct 2021 15:52:36 +0200
From:   Jan Kara <jack@...e.cz>
To:     Gabriel Krisman Bertazi <krisman@...labora.com>
Cc:     jack@...e.com, amir73il@...il.com, djwong@...nel.org,
        tytso@....edu, david@...morbit.com, dhowells@...hat.com,
        khazhy@...gle.com, linux-fsdevel@...r.kernel.org,
        linux-ext4@...r.kernel.org, linux-api@...r.kernel.org,
        kernel@...labora.com
Subject: Re: [PATCH v8 22/32] fanotify: Support merging of error events

On Mon 18-10-21 21:00:05, Gabriel Krisman Bertazi 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>

Looks good to me. Feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza


> ---
> 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
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR