[Devel] [CRIU] [PATCH v3] spfs, files-reg: symbolic links support
Alexander Mikhalitsyn
alexander.mikhalitsyn at virtuozzo.com
Fri Dec 27 12:01:21 MSK 2019
This patch adds support for symbolic links that located on NFS filesystem,
also it introduces support for ghost symbolic links located on non-NFS filesystems.
Caution: ghost symbolic links on NFS are not supported!
Fixes https://jira.sw.ru/browse/PSBM-99969
Signed-off-by: Alexander Mikhalitsyn <alexander.mikhalitsyn at virtuozzo.com>
Signed-off-by: Alexander Mikhalitsyn <alexander at mihalicyn.com>
---
criu/files-reg.c | 112 ++++++++++++++++++++++++++++++++++++++++++------
criu/spfs.c | 2 +-
images/ghost-file.proto | 2 +
3 files changed, 101 insertions(+), 15 deletions(-)
diff --git a/criu/files-reg.c b/criu/files-reg.c
index 0d8e2e3..908ce1b 100644
--- a/criu/files-reg.c
+++ b/criu/files-reg.c
@@ -315,19 +315,64 @@ static int mkreg_ghost(char *path, GhostFileEntry *gfe, struct cr_img *img)
return ret;
}
+static int mklnk_ghost(char *path, GhostFileEntry *gfe, struct cr_img *img)
+{
+ char *target_path = "CRIU_GHOST_SYMLINK_PLACEHOLDER";
+ int ret;
+
+ /*
+ * gfe->symlnk_target could be NULL, but in real we can't create
+ * symlink with empty target.
+ * If gfe->symlnk_target is NULL we have two possibilities:
+ * 1. We works with ghost symlink that was dumped without content
+ * => this symlink lives on spfs.
+ * This is not a problem to make it with fake target, because
+ * later spfs will be remounted to NFS and symlink will have
+ * original target.
+ * 2. We works with an old image => we couldn't correctly restore symlink
+ */
+ if (gfe->symlnk_target) {
+ target_path = gfe->symlnk_target;
+ } else {
+ pr_info("Symlink target is NULL for ghost symlink %s replacing it with placeholder\n", path);
+ }
+
+ ret = symlink(target_path, path);
+ if (ret < 0) {
+ pr_perror("Could not create ghost symlink %s\n", path);
+ return -1;
+ }
+
+ return 0;
+}
+
static int ghost_apply_metadata(const char *path, GhostFileEntry *gfe)
{
struct timeval tv[2];
int ret = -1;
- if (chown(path, gfe->uid, gfe->gid) < 0) {
- pr_perror("Can't reset user/group on ghost %s", path);
- goto err;
- }
+ if (S_ISLNK(gfe->mode)) {
+ if (lchown(path, gfe->uid, gfe->gid) < 0) {
+ pr_perror("Can't reset user/group on ghost %s", path);
+ goto err;
+ }
- if (chmod(path, gfe->mode)) {
- pr_perror("Can't set perms %o on ghost %s", gfe->mode, path);
- goto err;
+ /*
+ * We have no lchmod() function, and fchmod() will fail on
+ * O_PATH | O_NOFOLLOW fd. Yes, we have fchmodat()
+ * function and flag AT_SYMLINK_NOFOLLOW described in
+ * man 2 fchmodat, but it is not currently implemented. %)
+ */
+ } else {
+ if (chown(path, gfe->uid, gfe->gid) < 0) {
+ pr_perror("Can't reset user/group on ghost %s", path);
+ goto err;
+ }
+
+ if (chmod(path, gfe->mode)) {
+ pr_perror("Can't set perms %o on ghost %s", gfe->mode, path);
+ goto err;
+ }
}
if (gfe->atim) {
@@ -365,6 +410,9 @@ again:
} else if (S_ISDIR(gfe->mode)) {
if ((ret = mkdirpat(AT_FDCWD, path, gfe->mode)) < 0)
msg = "Can't make ghost dir";
+ } else if (S_ISLNK(gfe->mode)) {
+ if ((ret = mklnk_ghost(path, gfe, img)) < 0)
+ msg = "Can't create ghost symlink";
} else {
if ((ret = mkreg_ghost(path, gfe, img)) < 0)
msg = "Can't create ghost regfile";
@@ -1031,6 +1079,7 @@ static int dump_ghost_file(int _fd, u32 id, const struct stat *st,
struct cr_img *img;
GhostFileEntry gfe = GHOST_FILE_ENTRY__INIT;
Timeval atim = TIMEVAL__INIT, mtim = TIMEVAL__INIT;
+ int ret = -1;
pr_info("Dumping ghost file contents (id %#x)\n", id);
@@ -1064,11 +1113,41 @@ static int dump_ghost_file(int _fd, u32 id, const struct stat *st,
gfe.size = st->st_size;
}
- if (pb_write_one(img, &gfe, PB_GHOST_FILE))
- return -1;
+ /*
+ * We set gfe.symlnk_target only if we need to dump
+ * symlink content, otherwise we leave it NULL.
+ * It will be taken into account on restore in mklnk_ghost function.
+ */
+ if (S_ISLNK(st->st_mode) && dump_content) {
+ char pathbuf[PATH_MAX];
+
+ /*
+ * We assume that _fd opened with O_PATH | O_NOFOLLOW
+ * flags because S_ISLNK(st->st_mode). With current kernel version,
+ * it's looks like correct assumption in any case.
+ */
+ ret = readlinkat(_fd, "", pathbuf, sizeof(pathbuf));
+ if (ret < 0) {
+ pr_perror("Can't readlinkat");
+ goto exit_close_image;
+ }
+
+ pathbuf[ret] = 0;
+
+ if (ret != st->st_size) {
+ pr_err("Buffer for readlinkat is too small: ret %u, st_size %u, buf %u %s", (unsigned)ret, (unsigned)st->st_size, (unsigned)PATH_MAX, pathbuf);
+ goto exit_close_image;
+ }
+
+ gfe.symlnk_target = pathbuf;
+ ret = 0;
+ }
+
+ if ((ret = pb_write_one(img, &gfe, PB_GHOST_FILE)))
+ goto exit_close_image;
if (S_ISREG(st->st_mode) && dump_content) {
- int fd, ret;
+ int fd;
char lpath[PSFDS];
/*
@@ -1079,20 +1158,20 @@ static int dump_ghost_file(int _fd, u32 id, const struct stat *st,
fd = open(lpath, O_RDONLY);
if (fd < 0) {
pr_perror("Can't open ghost original file");
- return -1;
+ goto exit_close_image;
}
if (gfe.chunks)
ret = copy_file_to_chunks(fd, img, st->st_size);
else
ret = copy_file(fd, img_raw_fd(img), st->st_size);
+
close(fd);
- if (ret)
- return -1;
}
+exit_close_image:
close_image(img);
- return 0;
+ return ret ? -1 : 0;
}
struct file_remap *lookup_ghost_remap(u32 dev, u32 ino)
@@ -1537,6 +1616,11 @@ static int check_path_remap(struct fd_link *link, const struct fd_parms *parms,
}
if (ost->st_nlink == 0) {
+ if (spfs_file(parms, nsid)) {
+ pr_err("Ghost files on NFS are not supported\n");
+ return -1;
+ }
+
/*
* Unpleasant, but easy case. File is completely invisible
* from the FS. Just dump its contents and that's it. But
diff --git a/criu/spfs.c b/criu/spfs.c
index 730de13..20182c2 100644
--- a/criu/spfs.c
+++ b/criu/spfs.c
@@ -78,7 +78,7 @@ static int spfs_send_request(int sock, void *req, size_t len)
int spfs_remap_path(const char *path, const char *link_remap)
{
- if (setxattr(path, "security.spfs.link_remap", link_remap, strlen(link_remap) + 1, XATTR_CREATE)) {
+ if (lsetxattr(path, "security.spfs.link_remap", link_remap, strlen(link_remap) + 1, XATTR_CREATE)) {
pr_perror("failed to set xattr security.spfs.link_remap with value %s for file %s", link_remap, path);
return -1;
}
diff --git a/images/ghost-file.proto b/images/ghost-file.proto
index eda4664..0576089 100644
--- a/images/ghost-file.proto
+++ b/images/ghost-file.proto
@@ -15,6 +15,8 @@ message ghost_file_entry {
optional timeval mtim = 8;
optional bool chunks = 9;
optional uint64 size = 10;
+ /* this field makes sense only when S_ISLNK(mode) */
+ optional string symlnk_target = 11;
}
message ghost_chunk_entry {
--
1.8.3.1
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