[CRIU] [RFC] fsnotify: Do not track deleted watchees

[Cyrill Gorcunov]

If the watchee is deleted we might be able to
open in by file handle at checkpoint time but
fail on restore. And since we don't have any kernel's
interface to fetch and restore fsnotify event queue
simply ignore such watchees.

Once fsnotify queue c/r implemented need to revisit
this place.

Signed-off-by: Cyrill Gorcunov <gorcunov at openvz.org>
---
 fsnotify.c | 38 ++++++++++++++++++++++++++++++++++----
 1 file changed, 34 insertions(+), 4 deletions(-)

diff --git a/fsnotify.c b/fsnotify.c
index 476fb2620bd0..eb635da39157 100644
--- a/fsnotify.c
+++ b/fsnotify.c
@@ -132,9 +132,31 @@ int check_open_handle(unsigned int s_dev, unsigned long i_ino,
 
 	fd = open_handle(s_dev, i_ino, f_handle);
 	if (fd >= 0) {
+		struct stat st;
+
+		/*
+		 * WARNING
+		 *
+		 * The file might be accessible via dentry
+		 * cache but still deleted, which means we
+		 * might be fail on restore procedure. Thus
+		 * check for number of links. If the file
+		 * is deleted then we should simply ignore
+		 * it.
+		 *
+		 * FIXME Once the kernel will be updated
+		 * and c/r for fsnotify queue is implemented
+		 * need to fix this place as well.
+		 */
+		if (fstat(fd, &st) < 0) {
+			pr_perror("Can't stat fd %d", fd);
+			close(fd);
+			return -1;
+		}
 		close(fd);
-		pr_debug("\tHandle %x:%lx is openable\n", s_dev, i_ino);
-		return 0;
+		pr_debug("\tHandle %x:%lx is openable (st_nlink %lu)\n",
+			 s_dev, i_ino, st.st_nlink);
+		return st.st_nlink > 0 ? 0 : 1;
 	}
 
 	pr_warn("\tHandle %x:%lx cannot be opened\n", s_dev, i_ino);
@@ -152,6 +174,7 @@ int check_open_handle(unsigned int s_dev, unsigned long i_ino,
 static int dump_inotify_entry(union fdinfo_entries *e, void *arg)
 {
 	InotifyWdEntry *we = &e->ify;
+	int ret;
 
 	we->id = *(u32 *)arg;
 	pr_info("wd: wd 0x%08x s_dev 0x%08x i_ino 0x%16"PRIx64" mask 0x%08x\n",
@@ -160,8 +183,11 @@ static int dump_inotify_entry(union fdinfo_entries *e, void *arg)
 			we->f_handle->bytes, we->f_handle->type,
 			we->f_handle->handle[0], we->f_handle->handle[1]);
 
-	if (check_open_handle(we->s_dev, we->i_ino, we->f_handle))
+	ret = check_open_handle(we->s_dev, we->i_ino, we->f_handle);
+	if (ret < 0)
 		return -1;
+	else if (ret == 1)
+		return 0;
 
 	return pb_write_one(fdset_fd(glob_fdset, CR_FD_INOTIFY_WD), we, PB_INOTIFY_WD);
 }
@@ -206,6 +232,7 @@ static int dump_fanotify_entry(union fdinfo_entries *e, void *arg)
 	fme->id = fsn_params->id;
 
 	if (fme->type == MARK_TYPE__INODE) {
+		int ret;
 
 		BUG_ON(!fme->ie);
 
@@ -216,8 +243,11 @@ static int dump_fanotify_entry(union fdinfo_entries *e, void *arg)
 			fme->ie->f_handle->bytes, fme->ie->f_handle->type,
 			fme->ie->f_handle->handle[0], fme->ie->f_handle->handle[1]);
 
-		if (check_open_handle(fme->s_dev, fme->ie->i_ino, fme->ie->f_handle))
+		ret = check_open_handle(fme->s_dev, fme->ie->i_ino, fme->ie->f_handle);
+		if (ret < 0)
 			return -1;
+		else if (ret == 1)
+			return 0;
 	}
 
 	if (fme->type == MARK_TYPE__MOUNT) {
-- 
1.8.3.1