linux.git/include/net/9p, branch v7.2-rc1

9p: Cache negative dentries for lookup performance

2026-06-21T05:22:56+00:00

Not caching negative dentries can result in poor performance for
workloads that repeatedly look up non-existent paths. Each such
lookup triggers a full 9P transaction with the server, adding
unnecessary overhead.

A typical example is source compilation, where multiple cc1 processes
are spawned and repeatedly search for the same missing header files
over and over again.

This change enables caching of negative dentries, so that lookups for
known non-existent paths do not require a full 9P transaction. The
cached negative dentries are retained for a configurable duration
(expressed in milliseconds), as specified by the ndentry_timeout
field in struct v9fs_session_info. If set to -1, negative dentries
are cached indefinitely.

This optimization reduces lookup overhead and improves performance for
workloads involving frequent access to non-existent paths.

Signed-off-by: Remi Pommarel 
Message-ID: 
Signed-off-by: Dominique Martinet

9p: document missing enum values in kernel-doc comments

2026-04-16T02:57:01+00:00

Add kernel-doc entries for all undocumented enum values:
- p9_debug_flags: P9_DEBUG_CACHE, P9_DEBUG_MMAP
- p9_msg_t: all 9P2000.L message types (TLOPEN/RLOPEN through
  TUNLINKAT/RUNLINKAT)
- p9_open_mode_t: P9L_MODE_MASK, P9L_DIRECT, P9L_NOWRITECACHE,
  P9L_LOOSE

Assisted-by: Claude:claude-opus-4-6
Signed-off-by: Kit Dallege 
Reviewed-by: Christian Schoenebeck 
Message-ID: <20260315190633.73536-1-xaum.io@gmail.com>
Signed-off-by: Dominique Martinet

9p: convert to the new mount API

2025-11-03T07:49:53+00:00

Convert 9p to the new mount API. This patch consolidates all parsing
into fs/9p/v9fs.c, which stores all results into a filesystem context
which can be passed to the various transports as needed.

Some of the parsing helper functions such as get_cache_mode() have been
eliminated in favor of using the new mount API's enum param type,
for simplicity.

Signed-off-by: Eric Sandeen 
Message-ID: <20251010214222.1347785-5-sandeen@redhat.com>
[ Dominique: handled source explicitly as per follow-up discussion ]
Signed-off-by: Dominique Martinet

9p: create a v9fs_context structure to hold parsed options

2025-11-03T07:49:53+00:00

This patch creates a new v9fs_context structure which includes
new p9_session_opts and p9_client_opts structures, as well as
re-using the existing p9_fd_opts and p9_rdma_opts to store options
during parsing. The new structure will be used in the next
commit to pass all parsed options to the appropriate transports.

Signed-off-by: Eric Sandeen 
Message-ID: <20251010214222.1347785-4-sandeen@redhat.com>
Signed-off-by: Dominique Martinet

net/9p: move structures and macros to header files

2025-11-03T07:49:53+00:00

With the new mount API all option parsing will need to happen
in fs/v9fs.c, so move some existing data structures and macros
to header files to facilitate this. Rename some to reflect
the transport they are used for (rdma, fd, etc), for clarity.

Signed-off-by: Eric Sandeen 
Message-ID: <20251010214222.1347785-3-sandeen@redhat.com>
Signed-off-by: Dominique Martinet

net/9p: cleanup: change p9_trans_module->def to bool

2025-11-03T07:49:29+00:00

'->def' is only ever used as a true/false flag

Reported-by: Christophe JAILLET 
Message-ID: <20251103-v9fs_trans_def_bool-v1-1-f33dc7ed9e81@codewreck.org>
Signed-off-by: Dominique Martinet

9p: Use kvmalloc for message buffers on supported transports

2025-11-03T07:41:24+00:00

While developing a 9P server (https://github.com/Barre/ZeroFS) and
testing it under high-load, I was running into allocation failures.
The failures occur even with plenty of free memory available because
kmalloc requires contiguous physical memory.

This results in errors like:
ls: page allocation failure: order:7, mode:0x40c40(GFP_NOFS|__GFP_COMP)

This patch introduces a transport capability flag (supports_vmalloc)
that indicates whether a transport can work with vmalloc'd buffers
(non-physically contiguous memory). Transports requiring DMA should
leave this flag as false.

The fd-based transports (tcp, unix, fd) set this flag to true, and
p9_fcall_init will use kvmalloc instead of kmalloc for these
transports. This allows the allocator to fall back to vmalloc when
contiguous physical memory is not available.

Additionally, if kmem_cache_alloc fails, the code falls back to
kvmalloc for transports that support it.

Signed-off-by: Pierre Barre 
Reviewed-by: Christian Schoenebeck 
Message-ID: 
Signed-off-by: Dominique Martinet

netfs, 9p: Implement helpers for new write code

2024-05-01T17:07:37+00:00

Implement the helpers for the new write code in 9p.  There's now an
optional ->prepare_write() that allows the filesystem to set the parameters
for the next write, such as maximum size and maximum segment count, and an
->issue_write() that is called to initiate an (asynchronous) write
operation.

Signed-off-by: David Howells 
Reviewed-by: Jeff Layton 
cc: Eric Van Hensbergen 
cc: Latchesar Ionkov 
cc: Dominique Martinet 
cc: Christian Schoenebeck 
cc: v9fs@lists.linux.dev
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org

9p: Add additional debug flags and open modes

2023-03-27T02:33:48+00:00

Add some additional debug flags to assist with debugging
cache changes.  Also add some additional open modes so we
can track cache state in fids more directly.

Signed-off-by: Eric Van Hensbergen

net/9p: distinguish zero-copy requests

2022-12-05T22:30:55+00:00

Add boolean `zc` member to struct p9_fcall to distinguish zero-copy
messages (not using the linear `sdata` buffer for message payload) from
regular messages (which do copy message payload to `sdata` before being
further processed).

This new member is appended to end of structure to avoid inserting huge
padding in generated layout.

Link: https://lkml.kernel.org/r/8f2a5c12a446c3b544da64e0b1550e1fb2d6f972.1669144861.git.linux_oss@crudebyte.com
Signed-off-by: Christian Schoenebeck 
Tested-by: Stefano Stabellini 
Signed-off-by: Dominique Martinet