fanotify: Store fanotify handles differently

Currently, struct fanotify_fid groups fsid and file handle and is
unioned together with struct path to save space. Also there is fh_type
and fh_len directly in struct fanotify_event to avoid padding overhead.
In the follwing patches, we will be adding more event types and this
packing makes code difficult to follow. So unpack everything and create
struct fanotify_fh which groups members logically related to file handle
to make code easier to follow. In the following patch we will pack
things again differently to make events smaller.

Signed-off-by: Jan Kara <jack@suse.cz>

1 files changed, 63 insertions, 34 deletions

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 960f4f4d9e8f..64b05be4058d 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -17,6 +17,31 @@
 
 #include "fanotify.h"
 
+static bool fanotify_path_equal(struct path *p1, struct path *p2)
+{
+	return p1->mnt == p2->mnt && p1->dentry == p2->dentry;
+}
+
+static inline bool fanotify_fsid_equal(__kernel_fsid_t *fsid1,
+				       __kernel_fsid_t *fsid2)
+{
+	return fsid1->val[0] == fsid1->val[0] && fsid2->val[1] == fsid2->val[1];
+}
+
+static bool fanotify_fh_equal(struct fanotify_fh *fh1,
+			     struct fanotify_fh *fh2)
+{
+	if (fh1->type != fh2->type || fh1->len != fh2->len)
+		return false;
+
+	/* Do not merge events if we failed to encode fh */
+	if (fh1->type == FILEID_INVALID)
+		return false;
+
+	return !fh1->len ||
+		!memcmp(fanotify_fh_buf(fh1), fanotify_fh_buf(fh2), fh1->len);
+}
+
 static bool should_merge(struct fsnotify_event *old_fsn,
 			 struct fsnotify_event *new_fsn)
 {
@@ -27,12 +52,12 @@ static bool should_merge(struct fsnotify_event *old_fsn,
 	new = FANOTIFY_E(new_fsn);
 
 	if (old_fsn->objectid != new_fsn->objectid || old->pid != new->pid ||
-	    old->fh_type != new->fh_type || old->fh_len != new->fh_len)
+	    old->fh.type != new->fh.type)
 		return false;
 
 	if (fanotify_event_has_path(old)) {
-		return old->path.mnt == new->path.mnt &&
-			old->path.dentry == new->path.dentry;
+		return fanotify_path_equal(fanotify_event_path(old),
+					   fanotify_event_path(new));
 	} else if (fanotify_event_has_fid(old)) {
 		/*
 		 * We want to merge many dirent events in the same dir (i.e.
@@ -42,8 +67,11 @@ static bool should_merge(struct fsnotify_event *old_fsn,
 		 * mask FAN_CREATE|FAN_DELETE|FAN_ONDIR if it describes mkdir+
 		 * unlink pair or rmdir+create pair of events.
 		 */
-		return (old->mask & FS_ISDIR) == (new->mask & FS_ISDIR) &&
-			fanotify_fid_equal(&old->fid, &new->fid, old->fh_len);
+		if ((old->mask & FS_ISDIR) != (new->mask & FS_ISDIR))
+			return false;
+
+		return fanotify_fsid_equal(&old->fsid, &new->fsid) &&
+			fanotify_fh_equal(&old->fh, &new->fh);
 	}
 
 	/* Do not merge events if we failed to encode fid */
@@ -213,15 +241,14 @@ static u32 fanotify_group_event_mask(struct fsnotify_group *group,
 	return test_mask & user_mask;
 }
 
-static int fanotify_encode_fid(struct fanotify_event *event,
-			       struct inode *inode, gfp_t gfp,
-			       __kernel_fsid_t *fsid)
+static void fanotify_encode_fh(struct fanotify_fh *fh, struct inode *inode,
+			       gfp_t gfp)
 {
-	struct fanotify_fid *fid = &event->fid;
-	int dwords, bytes = 0;
-	int err, type;
+	int dwords, type, bytes = 0;
+	char *ext_buf = NULL;
+	void *buf = fh->buf;
+	int err;
 
-	fid->ext_fh = NULL;
 	dwords = 0;
 	err = -ENOENT;
 	type = exportfs_encode_inode_fh(inode, NULL, &dwords, NULL);
@@ -232,31 +259,32 @@ static int fanotify_encode_fid(struct fanotify_event *event,
 	if (bytes > FANOTIFY_INLINE_FH_LEN) {
 		/* Treat failure to allocate fh as failure to allocate event */
 		err = -ENOMEM;
-		fid->ext_fh = kmalloc(bytes, gfp);
-		if (!fid->ext_fh)
+		ext_buf = kmalloc(bytes, gfp);
+		if (!ext_buf)
 			goto out_err;
+
+		*fanotify_fh_ext_buf_ptr(fh) = ext_buf;
+		buf = ext_buf;
 	}
 
-	type = exportfs_encode_inode_fh(inode, fanotify_fid_fh(fid, bytes),
-					&dwords, NULL);
+	type = exportfs_encode_inode_fh(inode, buf, &dwords, NULL);
 	err = -EINVAL;
 	if (!type || type == FILEID_INVALID || bytes != dwords << 2)
 		goto out_err;
 
-	fid->fsid = *fsid;
-	event->fh_len = bytes;
+	fh->type = type;
+	fh->len = bytes;
 
-	return type;
+	return;
 
 out_err:
-	pr_warn_ratelimited("fanotify: failed to encode fid (fsid=%x.%x, "
-			    "type=%d, bytes=%d, err=%i)\n",
-			    fsid->val[0], fsid->val[1], type, bytes, err);
-	kfree(fid->ext_fh);
-	fid->ext_fh = NULL;
-	event->fh_len = 0;
-
-	return FILEID_INVALID;
+	pr_warn_ratelimited("fanotify: failed to encode fid (type=%d, len=%d, err=%i)\n",
+			    type, bytes, err);
+	kfree(ext_buf);
+	*fanotify_fh_ext_buf_ptr(fh) = NULL;
+	/* Report the event without a file identifier on encode error */
+	fh->type = FILEID_INVALID;
+	fh->len = 0;
 }
 
 /*
@@ -326,16 +354,17 @@ init: __maybe_unused
 		event->pid = get_pid(task_pid(current));
 	else
 		event->pid = get_pid(task_tgid(current));
-	event->fh_len = 0;
+	event->fh.len = 0;
 	if (id && FAN_GROUP_FLAG(group, FAN_REPORT_FID)) {
-		/* Report the event without a file identifier on encode error */
-		event->fh_type = fanotify_encode_fid(event, id, gfp, fsid);
+		event->fsid = *fsid;
+		if (id)
+			fanotify_encode_fh(&event->fh, id, gfp);
 	} else if (path) {
-		event->fh_type = FILEID_ROOT;
+		event->fh.type = FILEID_ROOT;
 		event->path = *path;
 		path_get(path);
 	} else {
-		event->fh_type = FILEID_INVALID;
+		event->fh.type = FILEID_INVALID;
 		event->path.mnt = NULL;
 		event->path.dentry = NULL;
 	}
@@ -483,8 +512,8 @@ static void fanotify_free_event(struct fsnotify_event *fsn_event)
 	event = FANOTIFY_E(fsn_event);
 	if (fanotify_event_has_path(event))
 		path_put(&event->path);
-	else if (fanotify_event_has_ext_fh(event))
-		kfree(event->fid.ext_fh);
+	else if (fanotify_fh_has_ext_buf(&event->fh))
+		kfree(fanotify_fh_ext_buf(&event->fh));
 	put_pid(event->pid);
 	if (fanotify_is_perm_event(event->mask)) {
 		kmem_cache_free(fanotify_perm_event_cachep,