[Qemu-devel] [PATCH 1/2] i_generation / st_gen support for local fs type

[Harsh Prateek Bora <harsh@linux.vnet.ibm.com>]

This patch provides support for st_gen for local fs type server.
Currently the support is provided for ext4, btrfs, reiserfs and xfs.

Signed-off-by: Harsh Prateek Bora <harsh@linux.vnet.ibm.com>
---
 fsdev/file-op-9p.h         |    7 +++++++
 hw/9pfs/cofile.c           |   22 ++++++++++++++++++++++
 hw/9pfs/virtio-9p-coth.h   |    2 ++
 hw/9pfs/virtio-9p-device.c |    1 +
 hw/9pfs/virtio-9p-local.c  |   32 +++++++++++++++++++++++++++++++-
 hw/9pfs/virtio-9p.c        |    9 +++++++++
 6 files changed, 72 insertions(+), 1 deletions(-)

diff --git a/fsdev/file-op-9p.h b/fsdev/file-op-9p.h
index a6940bb..e6a5055 100644
--- a/fsdev/file-op-9p.h
+++ b/fsdev/file-op-9p.h
@@ -49,6 +49,12 @@ typedef struct FsCred
 } FsCred;
 
 struct xattr_operations;
+struct FsContext;
+struct V9fsPath;
+
+typedef struct extended_ops {
+    int (*get_st_gen)(struct FsContext *, struct V9fsPath *, uint64_t *);
+} extended_ops;
 
 /* FsContext flag values */
 #define PATHNAME_FSCONTEXT 0x1
@@ -62,6 +68,7 @@ typedef struct FsContext
     int open_flags;
     int cache_model;
     struct xattr_operations **xops;
+    struct extended_ops exops;
     /* fs driver specific data */
     void *private;
 } FsContext;
diff --git a/hw/9pfs/cofile.c b/hw/9pfs/cofile.c
index 7ad4bec..bf7c44b 100644
--- a/hw/9pfs/cofile.c
+++ b/hw/9pfs/cofile.c
@@ -17,6 +17,28 @@
 #include "qemu-coroutine.h"
 #include "virtio-9p-coth.h"
 
+int v9fs_co_st_gen(V9fsPDU *pdu, V9fsPath *path, V9fsStatDotl *v9stat)
+{
+    int err;
+    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, &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;
diff --git a/hw/9pfs/virtio-9p-coth.h b/hw/9pfs/virtio-9p-coth.h
index 4630080..c9e9325 100644
--- a/hw/9pfs/virtio-9p-coth.h
+++ b/hw/9pfs/virtio-9p-coth.h
@@ -101,4 +101,6 @@ 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, V9fsStatDotl *v9stat);
+
 #endif
diff --git a/hw/9pfs/virtio-9p-device.c b/hw/9pfs/virtio-9p-device.c
index 246da23..6a969ba 100644
--- a/hw/9pfs/virtio-9p-device.c
+++ b/hw/9pfs/virtio-9p-device.c
@@ -122,6 +122,7 @@ VirtIODevice *virtio_9p_init(DeviceState *dev, V9fsConf *conf)
     }
     s->ctx.cache_model = fse->cache_model;
     s->ctx.fs_root = qemu_strdup(fse->path);
+    s->ctx.exops.get_st_gen = NULL;
     len = strlen(conf->tag);
     if (len > MAX_TAG_LEN) {
         len = MAX_TAG_LEN;
diff --git a/hw/9pfs/virtio-9p-local.c b/hw/9pfs/virtio-9p-local.c
index 1b6c323..2a2ddfa 100644
--- a/hw/9pfs/virtio-9p-local.c
+++ b/hw/9pfs/virtio-9p-local.c
@@ -20,6 +20,9 @@
 #include <sys/socket.h>
 #include <sys/un.h>
 #include <attr/xattr.h>
+#include <linux/fs.h>
+#include <linux/magic.h>
+#include <sys/ioctl.h>
 
 static int local_lstat(FsContext *fs_ctx, V9fsPath *fs_path, struct stat *stbuf)
 {
@@ -645,10 +648,37 @@ static int local_unlinkat(FsContext *ctx, V9fsPath *dir,
     return ret;
 }
 
+static int local_ioc_getversion(FsContext *ctx, V9fsPath *path, uint64_t *st_gen)
+{
+    int mode = 0600;
+    int fd;
+
+    fd = local_open(ctx, path, mode);
+    if(fd < 0) {
+        return fd;
+    }
+    return ioctl(fd, FS_IOC_GETVERSION, st_gen);
+
+}
+/* XFS_SUPER_MAGIC not available in linux/fs.h */
+#define XFS_SUPER_MAGIC 0x58465342
 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 EXT4_SUPER_MAGIC: /* same magic val for ext2/3 */
+        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 = {
diff --git a/hw/9pfs/virtio-9p.c b/hw/9pfs/virtio-9p.c
index 8b5e711..469668f 100644
--- a/hw/9pfs/virtio-9p.c
+++ b/hw/9pfs/virtio-9p.c
@@ -1357,6 +1357,15 @@ 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, &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:
-- 
1.7.1.1