hw/9pfs: Add st_gen support in getattr reply

This patch use file system specific ioctl for getting i_generation
value. Not all file system support the ioctl. So we add an export
specific extended operation and assign right callback for the
file system that support i_generation ioctl

["M. Mohan Kumar" <mohan@in.ibm.com> we can do ioctl only for
regular files and directories on the server]

Signed-off-by: Harsh Prateek Bora <harsh@linux.vnet.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

configure

@@ -2568,6 +2568,19 @@ if compile_prog "" "" ; then
     open_by_handle_at=yes
 fi
 
+########################################
+# check if we have linux/magic.h
+
+linux_magic_h=no
+cat > $TMPC << EOF
+#include <linux/magic.h>
+int main(void) {
+}
+EOF
+if compile_prog "" "" ; then
+    linux_magic_h=yes
+fi
+
 ##########################################
 # End of CC checks
 # After here, no more $cc or $ld runs
@@ -3051,6 +3064,10 @@ if test "$open_by_handle_at" = "yes" ; then
   echo "CONFIG_OPEN_BY_HANDLE=y" >> $config_host_mak
 fi
 
+if test "$linux_magic_h" = "yes" ; then
+  echo "CONFIG_LINUX_MAGIC_H=y" >> $config_host_mak
+fi
+
 # USB host support
 case "$usb" in
 linux)

fsdev/file-op-9p.h

@@ -49,6 +49,13 @@ typedef struct FsCred
 } FsCred;
 
 struct xattr_operations;
+struct FsContext;
+struct V9fsPath;
+
+typedef struct extended_ops {
+    int (*get_st_gen)(struct FsContext *, struct V9fsPath *,
+                      mode_t, uint64_t *);
+} extended_ops;
 
 /* FsContext flag values */
 #define PATHNAME_FSCONTEXT 0x1
@@ -64,6 +71,7 @@ typedef struct FsContext
     uid_t uid;
     int export_flags;
     struct xattr_operations **xops;
+    struct extended_ops exops;
     /* fs driver specific data */
     void *private;
 } FsContext;

hw/9pfs/cofile.c

@@ -17,6 +17,30 @@
 #include "qemu-coroutine.h"
 #include "virtio-9p-coth.h"
 
+int v9fs_co_st_gen(V9fsPDU *pdu, V9fsPath *path, mode_t st_mode,
+                   V9fsStatDotl *v9stat)
+{
+    int err = 0;
+    V9fsState *s = pdu->s;
+
+    if (v9fs_request_cancelled(pdu)) {
+        return -EINTR;
+    }
+    if (s->ctx.exops.get_st_gen) {
+        v9fs_path_read_lock(s);
+        v9fs_co_run_in_worker(
+            {
+                err = s->ctx.exops.get_st_gen(&s->ctx, path, st_mode,
+                                              &v9stat->st_gen);
+                if (err < 0) {
+                    err = -errno;
+                }
+            });
+        v9fs_path_unlock(s);
+    }
+    return err;
+}
+
 int v9fs_co_lstat(V9fsPDU *pdu, V9fsPath *path, struct stat *stbuf)
 {
     int err;

hw/9pfs/virtio-9p-coth.h

@@ -101,4 +101,7 @@ extern int v9fs_co_preadv(V9fsPDU *, V9fsFidState *,
                           struct iovec *, int, int64_t);
 extern int v9fs_co_name_to_path(V9fsPDU *, V9fsPath *,
                                 const char *, V9fsPath *);
+extern int v9fs_co_st_gen(V9fsPDU *pdu, V9fsPath *path, mode_t,
+                          V9fsStatDotl *v9stat);
+
 #endif

hw/9pfs/virtio-9p-device.c

@@ -117,6 +117,8 @@ VirtIODevice *virtio_9p_init(DeviceState *dev, V9fsConf *conf)
 
     s->ctx.export_flags = fse->export_flags;
     s->ctx.fs_root = g_strdup(fse->path);
+    s->ctx.exops.get_st_gen = NULL;
+
     len = strlen(conf->tag);
     if (len > MAX_TAG_LEN) {
         fprintf(stderr, "mount tag '%s' (%d bytes) is longer than "

hw/9pfs/virtio-9p-local.c

@@ -20,6 +20,24 @@
 #include <sys/socket.h>
 #include <sys/un.h>
 #include <attr/xattr.h>
+#include <linux/fs.h>
+#ifdef CONFIG_LINUX_MAGIC_H
+#include <linux/magic.h>
+#endif
+#include <sys/ioctl.h>
+
+#ifndef XFS_SUPER_MAGIC
+#define XFS_SUPER_MAGIC  0x58465342
+#endif
+#ifndef EXT2_SUPER_MAGIC
+#define EXT2_SUPER_MAGIC 0xEF53
+#endif
+#ifndef REISERFS_SUPER_MAGIC
+#define REISERFS_SUPER_MAGIC 0x52654973
+#endif
+#ifndef BTRFS_SUPER_MAGIC
+#define BTRFS_SUPER_MAGIC 0x9123683E
+#endif
 
 static int local_lstat(FsContext *fs_ctx, V9fsPath *fs_path, struct stat *stbuf)
 {
@@ -659,10 +677,44 @@ static int local_unlinkat(FsContext *ctx, V9fsPath *dir,
     return ret;
 }
 
+static int local_ioc_getversion(FsContext *ctx, V9fsPath *path,
+                                mode_t st_mode, uint64_t *st_gen)
+{
+    int err, fd;
+    /*
+     * Do not try to open special files like device nodes, fifos etc
+     * We can get fd for regular files and directories only
+     */
+    if (!S_ISREG(st_mode) && !S_ISDIR(st_mode)) {
+            return 0;
+    }
+    fd = local_open(ctx, path, O_RDONLY);
+    if (fd < 0) {
+        return fd;
+    }
+    err = ioctl(fd, FS_IOC_GETVERSION, st_gen);
+    local_close(ctx, fd);
+    return err;
+}
+
 static int local_init(FsContext *ctx)
 {
+    int err;
+    struct statfs stbuf;
+
     ctx->flags |= PATHNAME_FSCONTEXT;
-    return 0;
+    err = statfs(ctx->fs_root, &stbuf);
+    if (!err) {
+        switch (stbuf.f_type) {
+        case EXT2_SUPER_MAGIC:
+        case BTRFS_SUPER_MAGIC:
+        case REISERFS_SUPER_MAGIC:
+        case XFS_SUPER_MAGIC:
+            ctx->exops.get_st_gen = local_ioc_getversion;
+            break;
+        }
+    }
+    return err;
 }
 
 FileOperations local_ops = {

hw/9pfs/virtio-9p.c

@@ -1402,6 +1402,15 @@ static void v9fs_getattr(void *opaque)
         goto out;
     }
     stat_to_v9stat_dotl(s, &stbuf, &v9stat_dotl);
+
+    /*  fill st_gen if requested and supported by underlying fs */
+    if (request_mask & P9_STATS_GEN) {
+        retval = v9fs_co_st_gen(pdu, &fidp->path, stbuf.st_mode, &v9stat_dotl);
+        if (retval < 0) {
+            goto out;
+        }
+        v9stat_dotl.st_result_mask |= P9_STATS_GEN;
+    }
     retval = offset;
     retval += pdu_marshal(pdu, offset, "A", &v9stat_dotl);
 out: