[PATCH v4 07/19] liveupdate: Add helpers to track the files that LUO manages

[David Matlack <dmatlack@google.com>]

Add luo_track_file() and luo_untrack_file(), which add a file to and
remove it from luo_preserved_files, and use them instead of open-coding
xa_insert() and xa_erase() with luo_get_id() for preserved and retrieved
files.

The next commit lets file handlers make LUO track the file they retrieve
into, which adds more users. The helpers keep the key and the -EBUSY
behavior in one place.

No functional change intended.

Signed-off-by: David Matlack <dmatlack@google.com>
---
 kernel/liveupdate/luo_file.c | 32 ++++++++++++++++++++------------
 1 file changed, 20 insertions(+), 12 deletions(-)

diff --git a/kernel/liveupdate/luo_file.c b/kernel/liveupdate/luo_file.c
index e5d333649f76..91a2b74f71cb 100644
--- a/kernel/liveupdate/luo_file.c
+++ b/kernel/liveupdate/luo_file.c
@@ -192,6 +192,19 @@ static unsigned long luo_get_id(struct liveupdate_file_handler *fh,
 	return fh->ops->get_id ? fh->ops->get_id(file) : (unsigned long)file;
 }
 
+/* Make LUO manage @file, or fail with -EBUSY if it already does. */
+static int luo_track_file(struct liveupdate_file_handler *fh, struct file *file)
+{
+	return xa_insert(&luo_preserved_files, luo_get_id(fh, file), file,
+			 GFP_KERNEL);
+}
+
+static void luo_untrack_file(struct liveupdate_file_handler *fh,
+			     struct file *file)
+{
+	xa_erase(&luo_preserved_files, luo_get_id(fh, file));
+}
+
 static bool luo_token_is_used(struct luo_file_set *file_set, u64 token)
 {
 	struct luo_file *iter;
@@ -306,14 +319,13 @@ int luo_preserve_file(struct luo_file_set *file_set, u64 token, int fd,
 	if (err)
 		goto err_module_put;
 
-	err = xa_insert(&luo_preserved_files, luo_get_id(fh, file),
-			file, GFP_KERNEL);
+	err = luo_track_file(fh, file);
 	if (err)
 		goto err_free_arg;
 
 	err = luo_flb_file_preserve(fh);
 	if (err)
-		goto err_erase_xa;
+		goto err_untrack;
 
 	luo_file = kzalloc_obj(*luo_file);
 	if (!luo_file) {
@@ -345,8 +357,8 @@ int luo_preserve_file(struct luo_file_set *file_set, u64 token, int fd,
 	kfree(luo_file);
 err_flb_unpreserve:
 	luo_flb_file_unpreserve(fh);
-err_erase_xa:
-	xa_erase(&luo_preserved_files, luo_get_id(fh, file));
+err_untrack:
+	luo_untrack_file(fh, file);
 err_free_arg:
 	kfree(args.arg);
 err_module_put:
@@ -395,8 +407,7 @@ void luo_file_unpreserve_files(struct luo_file_set *file_set)
 		luo_file->fh->ops->unpreserve(&args);
 		luo_flb_file_unpreserve(luo_file->fh);
 
-		xa_erase(&luo_preserved_files,
-			 luo_get_id(luo_file->fh, luo_file->file));
+		luo_untrack_file(luo_file->fh, luo_file->file);
 		module_put(luo_file->fh->ops->owner);
 
 		list_del(&luo_file->list);
@@ -668,9 +679,7 @@ int luo_retrieve_file(struct luo_file_set *file_set, u64 token,
 		return err;
 	}
 
-	err = xa_insert(&luo_preserved_files,
-			luo_get_id(luo_file->fh, args.file), args.file,
-			GFP_KERNEL);
+	err = luo_track_file(luo_file->fh, args.file);
 	if (err) {
 		/* A retrieved file is new, so it can't be tracked already. */
 		WARN_ON_ONCE(err == -EBUSY);
@@ -788,8 +797,7 @@ int luo_file_finish(struct luo_file_set *file_set)
 		luo_file_finish_one(file_set, luo_file);
 
 		if (luo_file->file) {
-			xa_erase(&luo_preserved_files,
-				 luo_get_id(luo_file->fh, luo_file->file));
+			luo_untrack_file(luo_file->fh, luo_file->file);
 			fput(luo_file->file);
 		}
 		module_put(luo_file->fh->ops->owner);
-- 
2.56.0.542.g3ef89b7020-goog