memfd: don't reopen file descriptors for memory mappings

One memfd can be shared by a few restored files. Only of these files is restored with a file created with memfd_open. Others are restored by reopening memfd files via /proc/self/fd/. It seems unnecessary for restoring memfd memory mappings. We can always use the origin file. Signed-off-by: Andrei Vagin <[email protected]>
checkpoint-restore · Sep 23, 2023 · 1a94432 · 1a94432
1 parent 150eecc
commit 1a94432
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Showing 3 changed files with 12 additions and 6 deletions.
diff --git a/criu/files-reg.c b/criu/files-reg.c
@@ -2509,7 +2509,7 @@ static int open_filemap(int pid, struct vma_area *vma)
 			ret = dup(plugin_fd);
 		} else if (vma->e->status & VMA_AREA_MEMFD) {
 			if (!inherited_fd(vma->vmfd, &ret))
-				ret = memfd_open(vma->vmfd, &flags);
+				ret = memfd_open(vma->vmfd, &flags, true);
 		} else {
 			ret = open_path(vma->vmfd, do_open_reg_noseek_flags, &flags);
 		}

diff --git a/criu/include/memfd.h b/criu/include/memfd.h
@@ -1,7 +1,9 @@
 #ifndef __CR_MEMFD_H__
 #define __CR_MEMFD_H__
 
+#include <stdbool.h>
 #include <sys/stat.h>
+
 #include "int.h"
 #include "common/config.h"
 
@@ -12,7 +14,7 @@ extern int is_memfd(dev_t dev);
 extern int dump_one_memfd_cond(int lfd, u32 *id, struct fd_parms *parms);
 extern const struct fdtype_ops memfd_dump_ops;
 
-extern int memfd_open(struct file_desc *d, u32 *fdflags);
+extern int memfd_open(struct file_desc *d, u32 *fdflags, bool filemap);
 extern struct collect_image_info memfd_cinfo;
 extern struct file_desc *collect_memfd(u32 id);
 extern int apply_memfd_seals(void);

diff --git a/criu/memfd.c b/criu/memfd.c
@@ -323,7 +323,7 @@ static int memfd_open_inode(struct memfd_restore_inode *inode)
 	return fd;
 }
 
-int memfd_open(struct file_desc *d, u32 *fdflags)
+int memfd_open(struct file_desc *d, u32 *fdflags, bool filemap)
 {
 	struct memfd_info *mfi;
 	MemfdFileEntry *mfe;
@@ -342,6 +342,9 @@ int memfd_open(struct file_desc *d, u32 *fdflags)
 	/* Reopen the fd with original permissions */
 	flags = fdflags ? *fdflags : mfe->flags;
 
+	if (filemap && (flags & O_ACCMODE) == O_RDWR)
+		return fd;
+
 	if (!mfi->inode->was_opened_rw && (flags & O_ACCMODE) == O_RDWR) {
 		/*
 		 * If there is only a single RW-opened fd for a memfd, it can
@@ -352,7 +355,8 @@ int memfd_open(struct file_desc *d, u32 *fdflags)
 		 * and does execveat() from this memfd.
 		 */
 		if (!fcntl(fd, F_SETFL, flags)) {
-			mfi->inode->was_opened_rw = true;
+			if (!filemap)
+				mfi->inode->was_opened_rw = true;
 			return fd;
 		}
 
@@ -367,7 +371,7 @@ int memfd_open(struct file_desc *d, u32 *fdflags)
 	_fd = __open_proc(PROC_SELF, 0, flags, "fd/%d", fd);
 	if (_fd < 0)
 		pr_perror("Can't reopen memfd id=%d", mfe->id);
-	else if ((flags & O_ACCMODE) == O_RDWR)
+	else if (!filemap && (flags & O_ACCMODE) == O_RDWR)
 		pr_warn("execveat(fd=%d, ..., AT_EMPTY_PATH) might fail after restore; memfd id=%d\n", _fd, mfe->id);
 
 	close(fd);
@@ -382,7 +386,7 @@ static int memfd_open_fe_fd(struct file_desc *d, int *new_fd)
 	if (inherited_fd(d, new_fd))
 		return 0;
 
-	fd = memfd_open(d, NULL);
+	fd = memfd_open(d, NULL, false);
 	if (fd < 0)
 		return -1;