Patch "fanotify: Support merging of error events" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    fanotify: Support merging of error events

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     fanotify-support-merging-of-error-events.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 99b456d3fb0114ba6f9a46341cc70f08ed6470c1
Author: Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxx>
Date:   Mon Oct 25 16:27:36 2021 -0300

    fanotify: Support merging of error events
    
    [ Upstream commit 8a6ae64132fd27a944faed7bc38484827609eb76 ]
    
    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.
    
    Link: https://lore.kernel.org/r/20211025192746.66445-22-krisman@xxxxxxxxxxxxx
    Reviewed-by: Amir Goldstein <amir73il@xxxxxxxxx>
    Reviewed-by: Jan Kara <jack@xxxxxxx>
    Signed-off-by: Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxx>
    Signed-off-by: Jan Kara <jack@xxxxxxx>
    Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 1f195c95dfcd0..cedcb15468043 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 ebef952481fa0..2b032b79d5b06 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));
 }