passthrough_ll: add *xattr() operations

The extended attribute functionality is enabled with the "xattr" option
(default) and disabled with the "no_xatt" option.

New operations added:

 - getxattr
 - listxattr
 - setxattr
 - removexattr

Caveat: none of these operations will work on a symbolic link, because it's
difficult to implement that without races that can result in incorrect
operation.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

diff --git a/example/passthrough_ll.c b/example/passthrough_ll.c
index ba0f4afed664b8f04adfdddf7b2886673d7de5af..c46057ddbf2541058ea33a9c851b38fa866b6ce3 100644 (file)
--- a/example/passthrough_ll.c
+++ b/example/passthrough_ll.c
@@ -52,6 +52,7 @@
 #include <inttypes.h>
 #include <pthread.h>
 #include <sys/file.h>
+#include <sys/xattr.h>
 
 /* We are re-using pointers to our `struct lo_inode` and `struct
    lo_dirp` elements as inodes. This means that we must be able to
@@ -81,6 +82,7 @@ struct lo_data {
        int debug;
        int writeback;
        int flock;
+       int xattr;
        const char *source;
        struct lo_inode root; /* protected by lo->mutex */
 };
@@ -96,6 +98,10 @@ static const struct fuse_opt lo_opts[] = {
          offsetof(struct lo_data, flock), 1 },
        { "no_flock",
          offsetof(struct lo_data, flock), 0 },
+       { "xattr",
+         offsetof(struct lo_data, xattr), 1 },
+       { "no_xattr",
+         offsetof(struct lo_data, xattr), 0 },
 
        FUSE_OPT_END
 };
@@ -910,6 +916,182 @@ static void lo_flock(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi,
        fuse_reply_err(req, res == -1 ? errno : 0);
 }
 
+static void lo_getxattr(fuse_req_t req, fuse_ino_t ino, const char *name,
+                       size_t size)
+{
+       char *value = NULL;
+       char procname[64];
+       struct lo_inode *inode = lo_inode(req, ino);
+       ssize_t ret;
+       int saverr;
+
+       saverr = ENOSYS;
+       if (!lo_data(req)->xattr)
+               goto out;
+
+       if (lo_debug(req)) {
+               fprintf(stderr, "lo_getxattr(ino=%" PRIu64 ", name=%s size=%zd)\n",
+                       ino, name, size);
+       }
+
+       if (inode->is_symlink) {
+               /* Sorry, no race free way to getxattr on symlink. */
+               saverr = EPERM;
+               goto out;
+       }
+
+       sprintf(procname, "/proc/self/fd/%i", inode->fd);
+
+       if (size) {
+               value = malloc(size);
+               if (!value)
+                       goto out_err;
+
+               ret = getxattr(procname, name, value, size);
+               if (ret == -1)
+                       goto out_err;
+               saverr = 0;
+               if (ret == 0)
+                       goto out;
+
+               fuse_reply_buf(req, value, ret);
+       } else {
+               ret = getxattr(procname, name, NULL, 0);
+               if (ret == -1)
+                       goto out_err;
+
+               fuse_reply_xattr(req, ret);
+       }
+out_free:
+       free(value);
+       return;
+
+out_err:
+       saverr = errno;
+out:
+       fuse_reply_err(req, saverr);
+       goto out_free;
+}
+
+static void lo_listxattr(fuse_req_t req, fuse_ino_t ino, size_t size)
+{
+       char *value = NULL;
+       char procname[64];
+       struct lo_inode *inode = lo_inode(req, ino);
+       ssize_t ret;
+       int saverr;
+
+       saverr = ENOSYS;
+       if (!lo_data(req)->xattr)
+               goto out;
+
+       if (lo_debug(req)) {
+               fprintf(stderr, "lo_listxattr(ino=%" PRIu64 ", size=%zd)\n",
+                       ino, size);
+       }
+
+       if (inode->is_symlink) {
+               /* Sorry, no race free way to listxattr on symlink. */
+               saverr = EPERM;
+               goto out;
+       }
+
+       sprintf(procname, "/proc/self/fd/%i", inode->fd);
+
+       if (size) {
+               value = malloc(size);
+               if (!value)
+                       goto out_err;
+
+               ret = listxattr(procname, value, size);
+               if (ret == -1)
+                       goto out_err;
+               saverr = 0;
+               if (ret == 0)
+                       goto out;
+
+               fuse_reply_buf(req, value, ret);
+       } else {
+               ret = listxattr(procname, NULL, 0);
+               if (ret == -1)
+                       goto out_err;
+
+               fuse_reply_xattr(req, ret);
+       }
+out_free:
+       free(value);
+       return;
+
+out_err:
+       saverr = errno;
+out:
+       fuse_reply_err(req, saverr);
+       goto out_free;
+}
+
+static void lo_setxattr(fuse_req_t req, fuse_ino_t ino, const char *name,
+                       const char *value, size_t size, int flags)
+{
+       char procname[64];
+       struct lo_inode *inode = lo_inode(req, ino);
+       ssize_t ret;
+       int saverr;
+
+       saverr = ENOSYS;
+       if (!lo_data(req)->xattr)
+               goto out;
+
+       if (lo_debug(req)) {
+               fprintf(stderr, "lo_setxattr(ino=%" PRIu64 ", name=%s value=%s size=%zd)\n",
+                       ino, name, value, size);
+       }
+
+       if (inode->is_symlink) {
+               /* Sorry, no race free way to setxattr on symlink. */
+               saverr = EPERM;
+               goto out;
+       }
+
+       sprintf(procname, "/proc/self/fd/%i", inode->fd);
+
+       ret = setxattr(procname, name, value, size, flags);
+       saverr = ret == -1 ? errno : 0;
+
+out:
+       fuse_reply_err(req, saverr);
+}
+
+static void lo_removexattr(fuse_req_t req, fuse_ino_t ino, const char *name)
+{
+       char procname[64];
+       struct lo_inode *inode = lo_inode(req, ino);
+       ssize_t ret;
+       int saverr;
+
+       saverr = ENOSYS;
+       if (!lo_data(req)->xattr)
+               goto out;
+
+       if (lo_debug(req)) {
+               fprintf(stderr, "lo_removexattr(ino=%" PRIu64 ", name=%s)\n",
+                       ino, name);
+       }
+
+       if (inode->is_symlink) {
+               /* Sorry, no race free way to setxattr on symlink. */
+               saverr = EPERM;
+               goto out;
+       }
+
+       sprintf(procname, "/proc/self/fd/%i", inode->fd);
+
+       ret = removexattr(procname, name);
+       saverr = ret == -1 ? errno : 0;
+
+out:
+       fuse_reply_err(req, saverr);
+}
+
 static struct fuse_lowlevel_ops lo_oper = {
        .init           = lo_init,
        .lookup         = lo_lookup,
@@ -940,6 +1122,10 @@ static struct fuse_lowlevel_ops lo_oper = {
        .statfs         = lo_statfs,
        .fallocate      = lo_fallocate,
        .flock          = lo_flock,
+       .getxattr       = lo_getxattr,
+       .listxattr      = lo_listxattr,
+       .setxattr       = lo_setxattr,
+       .removexattr    = lo_removexattr,
 };
 
 int main(int argc, char *argv[])