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mkdir: if the destination exists atomically swap them

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if the destination already exists as it could not be properly cleaned
up, attempt to atomically swap the two directories and free the old
one.

Closes: https://github.com/containers/fuse-overlayfs/issues/213

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>
This commit is contained in:
Giuseppe Scrivano 2020-06-17 15:00:07 +02:00
parent f3e4154078
commit f26f1f71ae
No known key found for this signature in database
GPG Key ID: E4730F97F60286ED
1 changed files with 84 additions and 66 deletions
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150
main.c
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@ -823,7 +823,7 @@ drop_node_from_ino (Hash_table *inodes, struct ovl_node *node)
}
static int
direct_renameat2 (struct ovl_layer *l, int olddirfd, const char *oldpath,
direct_renameat2 (int olddirfd, const char *oldpath,
int newdirfd, const char *newpath, unsigned int flags)
{
return syscall (SYS_renameat2, olddirfd, oldpath, newdirfd, newpath, flags);
@ -2393,6 +2393,67 @@ copy_xattr (int sfd, int dfd, char *buf, size_t buf_size)
return 0;
}
static int
empty_dirfd (int fd)
{
cleanup_dir DIR *dp = NULL;
struct dirent *dent;
dp = fdopendir (fd);
if (dp == NULL)
{
close (fd);
return -1;
}
for (;;)
{
int ret;
errno = 0;
dent = readdir (dp);
if (dent == NULL)
{
if (errno)
return -1;
break;
}
if (strcmp (dent->d_name, ".") == 0)
continue;
if (strcmp (dent->d_name, "..") == 0)
continue;
ret = unlinkat (dirfd (dp), dent->d_name, 0);
if (ret < 0 && errno == EISDIR)
{
ret = unlinkat (dirfd (dp), dent->d_name, AT_REMOVEDIR);
if (ret < 0 && errno == ENOTEMPTY)
{
int dfd;
dfd = safe_openat (dirfd (dp), dent->d_name, O_DIRECTORY, 0);
if (dfd < 0)
return -1;
ret = empty_dirfd (dfd);
if (ret < 0)
return -1;
ret = unlinkat (dirfd (dp), dent->d_name, AT_REMOVEDIR);
if (ret < 0)
return -1;
continue;
}
}
if (ret < 0)
return ret;
}
return 0;
}
static int create_node_directory (struct ovl_data *lo, struct ovl_node *src);
static int
@ -2482,6 +2543,24 @@ create_directory (struct ovl_data *lo, int dirfd, const char *name, const struct
ret = renameat (lo->workdir_fd, wd_tmp_file_name, dirfd, name);
if (ret < 0)
{
if (errno == EEXIST)
{
int dfd = -1;
ret = direct_renameat2 (lo->workdir_fd, wd_tmp_file_name, dirfd, name, RENAME_EXCHANGE);
if (ret < 0)
goto out;
dfd = TEMP_FAILURE_RETRY (safe_openat (lo->workdir_fd, wd_tmp_file_name, O_DIRECTORY, 0));
if (dfd < 0)
return -1;
ret = empty_dirfd (dfd);
if (ret < 0)
goto out;
return unlinkat (lo->workdir_fd, wd_tmp_file_name, AT_REMOVEDIR);
}
if (errno == ENOTDIR)
unlinkat (dirfd, name, 0);
if (errno == ENOENT && parent)
@ -2816,67 +2895,6 @@ update_paths (struct ovl_node *node)
return 0;
}
static int
empty_dirfd (int fd)
{
cleanup_dir DIR *dp = NULL;
struct dirent *dent;
dp = fdopendir (fd);
if (dp == NULL)
{
close (fd);
return -1;
}
for (;;)
{
int ret;
errno = 0;
dent = readdir (dp);
if (dent == NULL)
{
if (errno)
return -1;
break;
}
if (strcmp (dent->d_name, ".") == 0)
continue;
if (strcmp (dent->d_name, "..") == 0)
continue;
ret = unlinkat (dirfd (dp), dent->d_name, 0);
if (ret < 0 && errno == EISDIR)
{
ret = unlinkat (dirfd (dp), dent->d_name, AT_REMOVEDIR);
if (ret < 0 && errno == ENOTEMPTY)
{
int dfd;
dfd = safe_openat (dirfd (dp), dent->d_name, O_DIRECTORY, 0);
if (dfd < 0)
return -1;
ret = empty_dirfd (dfd);
if (ret < 0)
return -1;
ret = unlinkat (dirfd (dp), dent->d_name, AT_REMOVEDIR);
if (ret < 0)
return -1;
continue;
}
}
if (ret < 0)
return ret;
}
return 0;
}
static int
empty_dir (struct ovl_layer *l, const char *path)
{
@ -4006,7 +4024,7 @@ ovl_rename_exchange (fuse_req_t req, fuse_ino_t parent, const char *name,
goto error;
ret = direct_renameat2 (node->layer, srcfd, name, destfd, newname, flags);
ret = direct_renameat2 (srcfd, name, destfd, newname, flags);
if (ret < 0)
goto error;
@ -4179,7 +4197,7 @@ ovl_rename_direct (fuse_req_t req, fuse_ino_t parent, const char *name,
so that with one operation we get both the rename and the whiteout created. */
if (destnode_is_whiteout)
{
ret = direct_renameat2 (get_upper_layer (lo), srcfd, name, destfd, newname, flags|RENAME_EXCHANGE);
ret = direct_renameat2 (srcfd, name, destfd, newname, flags|RENAME_EXCHANGE);
if (ret == 0)
goto done;
@ -4199,11 +4217,11 @@ ovl_rename_direct (fuse_req_t req, fuse_ino_t parent, const char *name,
/* Try to create the whiteout atomically, if it fails do the
rename+mknod separately. */
ret = direct_renameat2 (get_upper_layer (lo), srcfd, name, destfd,
ret = direct_renameat2 (srcfd, name, destfd,
newname, flags|RENAME_WHITEOUT);
if (ret < 0)
{
ret = direct_renameat2 (get_upper_layer (lo), srcfd, name, destfd,
ret = direct_renameat2 (srcfd, name, destfd,
newname, flags);
if (ret < 0)
goto error;