[PATCH v3 3/6] 9pfs: Introduce ftruncate file op

[Greg Kurz <groug@kaod.org>]

Add an ftruncate operation to the fs driver and use if when a fid has
a valid file descriptor. This is required to support more cases where
the client wants to do an action on an unlinked file which it still
has an open file decriptor for.

Only 9P2000.L was considered.

Reviewed-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
Signed-off-by: Greg Kurz <groug@kaod.org>

v2: - moved v9fs_co_ftruncate() near v9fs_co_truncate() in coth.h
    - similar change in file-op-9p.h

v3: - rename to fid_has_valid_file_handle()
---
 fsdev/file-op-9p.h |  2 ++
 hw/9pfs/9p-local.c |  9 +++++++++
 hw/9pfs/9p-synth.c |  8 ++++++++
 hw/9pfs/9p.c       |  6 +++++-
 hw/9pfs/cofs.c     | 18 ++++++++++++++++++
 hw/9pfs/coth.h     |  2 ++
 6 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/fsdev/file-op-9p.h b/fsdev/file-op-9p.h
index b815cea44e85..26ba1438c0ed 100644
--- a/fsdev/file-op-9p.h
+++ b/fsdev/file-op-9p.h
@@ -152,6 +152,8 @@ struct FileOperations {
     int (*fstat)(FsContext *, int, V9fsFidOpenState *, struct stat *);
     int (*rename)(FsContext *, const char *, const char *);
     int (*truncate)(FsContext *, V9fsPath *, off_t);
+    int (*ftruncate)(FsContext *ctx, int fid_type, V9fsFidOpenState *fs,
+                     off_t size);
     int (*fsync)(FsContext *, int, V9fsFidOpenState *, int);
     int (*statfs)(FsContext *s, V9fsPath *path, struct statfs *stbuf);
     ssize_t (*lgetxattr)(FsContext *, V9fsPath *,
diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c
index b16132299f2c..0b33da8d2a46 100644
--- a/hw/9pfs/9p-local.c
+++ b/hw/9pfs/9p-local.c
@@ -1042,6 +1042,14 @@ static int local_truncate(FsContext *ctx, V9fsPath *fs_path, off_t size)
     return ret;
 }
 
+static int local_ftruncate(FsContext *ctx, int fid_type, V9fsFidOpenState *fs,
+                           off_t size)
+{
+    int fd = local_fid_fd(fid_type, fs);
+
+    return ftruncate(fd, size);
+}
+
 static int local_chown(FsContext *fs_ctx, V9fsPath *fs_path, FsCred *credp)
 {
     char *dirpath = g_path_get_dirname(fs_path->data);
@@ -1617,4 +1625,5 @@ FileOperations local_ops = {
     .renameat  = local_renameat,
     .unlinkat = local_unlinkat,
     .has_valid_file_handle = local_has_valid_file_handle,
+    .ftruncate = local_ftruncate,
 };
diff --git a/hw/9pfs/9p-synth.c b/hw/9pfs/9p-synth.c
index be0492b400e1..3d28afc4d03d 100644
--- a/hw/9pfs/9p-synth.c
+++ b/hw/9pfs/9p-synth.c
@@ -356,6 +356,13 @@ static int synth_truncate(FsContext *ctx, V9fsPath *path, off_t offset)
     return -1;
 }
 
+static int synth_ftruncate(FsContext *ctx, int fid_type, V9fsFidOpenState *fs,
+                           off_t size)
+{
+    errno = ENOSYS;
+    return -1;
+}
+
 static int synth_chmod(FsContext *fs_ctx, V9fsPath *path, FsCred *credp)
 {
     errno = EPERM;
@@ -656,4 +663,5 @@ FileOperations synth_ops = {
     .renameat     = synth_renameat,
     .unlinkat     = synth_unlinkat,
     .has_valid_file_handle = synth_has_valid_file_handle,
+    .ftruncate    = synth_ftruncate,
 };
diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
index 9e4756c535f5..592477bdc45a 100644
--- a/hw/9pfs/9p.c
+++ b/hw/9pfs/9p.c
@@ -1733,7 +1733,11 @@ static void coroutine_fn v9fs_setattr(void *opaque)
         }
     }
     if (v9iattr.valid & (P9_ATTR_SIZE)) {
-        err = v9fs_co_truncate(pdu, &fidp->path, v9iattr.size);
+        if (fid_has_valid_file_handle(pdu->s, fidp)) {
+            err = v9fs_co_ftruncate(pdu, fidp, v9iattr.size);
+        } else {
+            err = v9fs_co_truncate(pdu, &fidp->path, v9iattr.size);
+        }
         if (err < 0) {
             goto out;
         }
diff --git a/hw/9pfs/cofs.c b/hw/9pfs/cofs.c
index 67e3ae5c5ccd..893466fb1a44 100644
--- a/hw/9pfs/cofs.c
+++ b/hw/9pfs/cofs.c
@@ -184,6 +184,24 @@ int coroutine_fn v9fs_co_truncate(V9fsPDU *pdu, V9fsPath *path, off_t size)
     return err;
 }
 
+int coroutine_fn v9fs_co_ftruncate(V9fsPDU *pdu, V9fsFidState *fidp, off_t size)
+{
+    int err;
+    V9fsState *s = pdu->s;
+
+    if (v9fs_request_cancelled(pdu)) {
+        return -EINTR;
+    }
+    v9fs_co_run_in_worker(
+        {
+            err = s->ops->ftruncate(&s->ctx, fidp->fid_type, &fidp->fs, size);
+            if (err < 0) {
+                err = -errno;
+            }
+        });
+    return err;
+}
+
 int coroutine_fn v9fs_co_mknod(V9fsPDU *pdu, V9fsFidState *fidp,
                                V9fsString *name, uid_t uid, gid_t gid,
                                dev_t dev, mode_t mode, struct stat *stbuf)
diff --git a/hw/9pfs/coth.h b/hw/9pfs/coth.h
index 2c54249b3577..62e922dc12e3 100644
--- a/hw/9pfs/coth.h
+++ b/hw/9pfs/coth.h
@@ -73,6 +73,8 @@ int coroutine_fn v9fs_co_chmod(V9fsPDU *, V9fsPath *, mode_t);
 int coroutine_fn v9fs_co_utimensat(V9fsPDU *, V9fsPath *, struct timespec [2]);
 int coroutine_fn v9fs_co_chown(V9fsPDU *, V9fsPath *, uid_t, gid_t);
 int coroutine_fn v9fs_co_truncate(V9fsPDU *, V9fsPath *, off_t);
+int coroutine_fn v9fs_co_ftruncate(V9fsPDU *pdu, V9fsFidState *fidp,
+                                   off_t size);
 int coroutine_fn v9fs_co_llistxattr(V9fsPDU *, V9fsPath *, void *, size_t);
 int coroutine_fn v9fs_co_lgetxattr(V9fsPDU *, V9fsPath *,
                                    V9fsString *, void *, size_t);
-- 
2.48.1