migration/qemu-file: switch buffer_at functions to positioned I/O _all helpers

qemu_put_buffer_at() and qemu_get_buffer_at() have the same pattern as
the bug fixed in multifd_file_recv_data(): the ssize_t return value from
the channel layer is stored in a size_t variable, and a short transfer
would be mishandled rather than retried.

Switch to qio_channel_pwrite_all() / qio_channel_pread_all() which
handle short transfers internally and make the code more robust and
consistent with the rest of the positioned I/O call sites.

Fixes: 7f5b50a401 ("migration/qemu-file: add utility methods for working with seekable channels")
Signed-off-by: Junjie Cao <junjie.cao@intel.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Link: https://lore.kernel.org/qemu-devel/20260420201317.30199-2-junjie.cao@intel.com
Signed-off-by: Fabiano Rosas <farosas@suse.de>

diff --git a/migration/qemu-file.c b/migration/qemu-file.c
index 9cf7dc3bd5c4677b50f8da6f85b4c78f94092919..9dfb202203c2d063ed186cd4cb602248cb87e8cd 100644 (file)
--- a/migration/qemu-file.c
+++ b/migration/qemu-file.c
@@ -535,28 +535,13 @@ void qemu_put_buffer_at(QEMUFile *f, const uint8_t *buf, size_t buflen,
                         off_t pos)
 {
     Error *err = NULL;
-    size_t ret;
 
     if (f->last_error) {
         return;
     }
 
     qemu_fflush(f);
-    ret = qio_channel_pwrite(f->ioc, (char *)buf, buflen, pos, &err);
-
-    if (err) {
-        qemu_file_set_error_obj(f, -EIO, err);
-        return;
-    }
-
-    if ((ssize_t)ret == QIO_CHANNEL_ERR_BLOCK) {
-        qemu_file_set_error_obj(f, -EAGAIN, NULL);
-        return;
-    }
-
-    if (ret != buflen) {
-        error_setg(&err, "Partial write of size %zu, expected %zu", ret,
-                   buflen);
+    if (qio_channel_pwrite_all(f->ioc, buf, buflen, pos, &err) < 0) {
         qemu_file_set_error_obj(f, -EIO, err);
         return;
     }
@@ -569,31 +554,17 @@ size_t qemu_get_buffer_at(QEMUFile *f, const uint8_t *buf, size_t buflen,
                           off_t pos)
 {
     Error *err = NULL;
-    size_t ret;
 
     if (f->last_error) {
         return 0;
     }
 
-    ret = qio_channel_pread(f->ioc, (char *)buf, buflen, pos, &err);
-
-    if ((ssize_t)ret == -1 || err) {
+    if (qio_channel_pread_all(f->ioc, (char *)buf, buflen, pos, &err) < 0) {
         qemu_file_set_error_obj(f, -EIO, err);
         return 0;
     }
 
-    if ((ssize_t)ret == QIO_CHANNEL_ERR_BLOCK) {
-        qemu_file_set_error_obj(f, -EAGAIN, NULL);
-        return 0;
-    }
-
-    if (ret != buflen) {
-        error_setg(&err, "Partial read of size %zu, expected %zu", ret, buflen);
-        qemu_file_set_error_obj(f, -EIO, err);
-        return 0;
-    }
-
-    return ret;
+    return buflen;
 }
 
 void qemu_set_offset(QEMUFile *f, off_t off, int whence)