hw/9pfs: add max_xattr option

Previous patch introduced a limit of max. 1024 simultaneous xattr FIDs.

This patch introduces an option "max_attr" that allows to override this
limit, just for the case that some user might run into this limit for
some reason, even if unlikely; or for reducing the limit further down
(e.g. that default limit of 1024 would cap at max. 64 MiB host memory,
at least on Linux hosts where the limit per xattr is 64k).

This new "max_xattr" option can be specified with both -fsdev and
-virtfs command line options, with the "local" and the "synth" fs
drivers.

The previous limit of 1024 is preserved as the default value.

Link: https://lore.kernel.org/qemu-devel/b7631ac0d8dde0629bc7c4f2c4185d9f57b962b4.1781361555.git.qemu_oss@crudebyte.com
Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com>

1 files changed, 6 insertions, 1 deletions

diff --git a/system/vl.c b/system/vl.c
index 1c0da7df29..1d14e2e207 100644
--- a/system/vl.c
+++ b/system/vl.c
@@ -3260,7 +3260,7 @@ void qemu_init(int argc, char **argv)
                 QemuOpts *fsdev;
                 QemuOpts *device;
                 const char *writeout, *sock_fd, *socket, *path, *security_model,
-                           *multidevs;
+                           *multidevs, *max_xattr_str;
 
                 olist = qemu_find_opts("virtfs");
                 if (!olist) {
@@ -3324,6 +3324,11 @@ void qemu_init(int argc, char **argv)
                 if (multidevs) {
                     qemu_opt_set(fsdev, "multidevs", multidevs, &error_abort);
                 }
+                max_xattr_str = qemu_opt_get(opts, "max_xattr");
+                if (max_xattr_str) {
+                    qemu_opt_set(fsdev, "max_xattr", max_xattr_str,
+                                 &error_abort);
+                }
                 device = qemu_opts_create(qemu_find_opts("device"), NULL, 0,
                                           &error_abort);
                 qemu_opt_set(device, "driver", "virtio-9p-pci", &error_abort);