[3/4] 9pfs: Introduce ftruncate file op

Commit Message

Greg Kurz March 10, 2025, 5:11 p.m. UTC

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.

Signed-off-by: Greg Kurz <[e-mail]>
---
 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(-)

Patch

diff --git a/fsdev/file-op-9p.h b/fsdev/file-op-9p.h
index 39fee185f4ce..40a40f7d8af8 100644
--- a/fsdev/file-op-9p.h
+++ b/fsdev/file-op-9p.h
@@ -165,6 +165,8 @@  struct FileOperations {
                     V9fsPath *newdir, const char *new_name);
     int (*unlinkat)(FsContext *ctx, V9fsPath *dir, const char *name, int flags);
     bool (*has_valid_handle)(int fid_type, V9fsFidOpenState *fs);
+    int (*ftruncate)(FsContext *ctx, int fid_type, V9fsFidOpenState *fs,
+                     off_t size);
 };
 
 #endif
diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c
index 03e5304ef888..fa763b0662f5 100644
--- a/hw/9pfs/9p-local.c
+++ b/hw/9pfs/9p-local.c
@@ -1046,6 +1046,14 @@  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);
@@ -1619,4 +1627,5 @@  FileOperations local_ops = {
     .renameat  = local_renameat,
     .unlinkat = local_unlinkat,
     .has_valid_handle = local_has_valid_handle,
+    .ftruncate = local_ftruncate,
 };
diff --git a/hw/9pfs/9p-synth.c b/hw/9pfs/9p-synth.c
index fa0b187a1b80..7f0e13f0ddd8 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_handle = synth_has_valid_handle,
+    .ftruncate    = synth_ftruncate,
 };
diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
index 969fb2f8c494..35b2ed900a01 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_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..0b8ee4c56495 100644
--- a/hw/9pfs/coth.h
+++ b/hw/9pfs/coth.h
@@ -109,5 +109,7 @@  int coroutine_fn v9fs_co_name_to_path(V9fsPDU *, V9fsPath *,
                                       const char *, V9fsPath *);
 int coroutine_fn v9fs_co_st_gen(V9fsPDU *pdu, V9fsPath *path, mode_t,
                                 V9fsStatDotl *v9stat);
+int coroutine_fn v9fs_co_ftruncate(V9fsPDU *pdu, V9fsFidState *fidp,
+                                   off_t size);
 
 #endif