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charset="us-ascii" Content-ID: <5B8AC616150808408665ED3086852C99@namprd12.prod.outlook.com> Content-Transfer-Encoding: quoted-printable Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: PH8PR12MB8431.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 0103ca96-4559-4fc7-51d5-08dea6ee13cf X-MS-Exchange-CrossTenant-originalarrivaltime: 30 Apr 2026 19:24:19.7547 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: xSjBcOhI/iByZYoawnJc6GXTfbI8wZHQMa1g+WSnn4VCbc200ZHMSV0ei6EElXjrJcO5CTtTzMtrAWNB5O7tDw== X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW4PR12MB7481 > On Apr 29, 2026, at 02:27, Miklos Szeredi wrote: >=20 > On Wed, 29 Apr 2026 at 01:30, Matthew R. Ochs wrote: >=20 >> The larger buffer is also currently supplied as a kvec output argument. >> For virtiofs, kvec arguments are copied through req->argbuf, which is >> allocated with kmalloc(..., GFP_ATOMIC). A large readdir buffer can >> therefore require a multi-megabyte contiguous atomic allocation and fail >> with -ENOMEM. >=20 > Shouldn't this be max_read? Here "read" and "write" refer to > direction of I/O on the filesystem, not on the fuse device (see > fuse/file.c) Thanks, the read/write direction point makes sense. I tested changing the cap to fc->max_read only, but that reproduces the original virtiofs failure on the 4K-host/64K-guest setup. The runtime values for the failing READDIR are: PAGE_SIZE=3D65536 fc->max_pages=3D124 fc->max_read=3D4294967295 fc->max_write=3D1048576 max_bufsize=3D8126464 nr_pages=3D124 So for this virtiofs mount, fc->max_read is effectively unlimited, while virtiofsd advertises its 1 MiB MAX_BUFFER_SIZE through max_write and rejects READDIR sizes above that limit. Do you prefer handling this locally in fuse_readdir_uncached(), for example by capping the request with all available limits: min3_t(size_t, fc->max_pages << PAGE_SHIFT, fc->max_read, fc->max_write) Or should virtiofs/FUSE instead make fc->max_read reflect this byte-sized buffer limit before readdir uses it? I will address the other cleanup comments in v3: drop the cast, keep the clamp-style sizing, use release_pages(), and remove the nomem double jump. -matt