lwn.git/fs/nfsd/nfsctl.c, branch docs-5.17-3

NFSD: Clean up the nfsd_net::nfssvc_boot field

2022-01-08T19:42:02+00:00

There are two boot-time fields in struct nfsd_net: one called boot_time and one called nfssvc_boot. The latter is used only to form write verifiers, but its documenting comment declares: /* Time of server startup */ Since commit 27c438f53e79 ("nfsd: Support the server resetting the boot verifier"), this field can be reset at any time; it's no longer tied to server restart. So that comment is stale. Also, according to pahole, struct timespec64 is 16 bytes long on x86_64. The nfssvc_boot field is used only to form a write verifier, which is 8 bytes long. Let's clarify this situation by manufacturing an 8-byte verifier in nfs_reset_boot_verifier() and storing only that in struct nfsd_net. We're grabbing 128 bits of time, so compress all of those into a 64-bit verifier instead of throwing out the high-order bits. In the future, the siphash_key can be re-used for other hashed objects per-nfsd_net. Signed-off-by: Chuck Lever

NFSD: simplify locking for network notifier.

2021-12-13T18:42:54+00:00

nfsd currently maintains an open-coded read/write semaphore (refcount and wait queue) for each network namespace to ensure the nfs service isn't shut down while the notifier is running. This is excessive. As there is unlikely to be contention between notifiers and they run without sleeping, a single spinlock is sufficient to avoid problems. Signed-off-by: NeilBrown [ cel: ensure nfsd_notifier_lock is static ] Signed-off-by: Chuck Lever

SUNRPC: stop using ->sv_nrthreads as a refcount

2021-12-13T18:42:51+00:00

The use of sv_nrthreads as a general refcount results in clumsy code, as is seen by various comments needed to explain the situation. This patch introduces a 'struct kref' and uses that for reference counting, leaving sv_nrthreads to be a pure count of threads. The kref is managed particularly in svc_get() and svc_put(), and also nfsd_put(); svc_destroy() now takes a pointer to the embedded kref, rather than to the serv. nfsd allows the svc_serv to exist with ->sv_nrhtreads being zero. This happens when a transport is created before the first thread is started. To support this, a 'keep_active' flag is introduced which holds a ref on the svc_serv. This is set when any listening socket is successfully added (unless there are running threads), and cleared when the number of threads is set. So when the last thread exits, the nfs_serv will be destroyed. The use of 'keep_active' replaces previous code which checked if there were any permanent sockets. We no longer clear ->rq_server when nfsd() exits. This was done to prevent svc_exit_thread() from calling svc_destroy(). Instead we take an extra reference to the svc_serv to prevent svc_destroy() from being called. Signed-off-by: NeilBrown Signed-off-by: Chuck Lever

SUNRPC/NFSD: clean up get/put functions.

2021-12-13T18:42:50+00:00

svc_destroy() is poorly named - it doesn't necessarily destroy the svc, it might just reduce the ref count. nfsd_destroy() is poorly named for the same reason. This patch: - removes the refcount functionality from svc_destroy(), moving it to a new svc_put(). Almost all previous callers of svc_destroy() now call svc_put(). - renames nfsd_destroy() to nfsd_put() and improves the code, using the new svc_destroy() rather than svc_put() - removes a few comments that explain the important for balanced get/put calls. This should be obvious. The only non-trivial part of this is that svc_destroy() would call svc_sock_update() on a non-final decrement. It can no longer do that, and svc_put() isn't really a good place of it. This call is now made from svc_exit_thread() which seems like a good place. This makes the call *before* sv_nrthreads is decremented rather than after. This is not particularly important as the call just sets a flag which causes sv_nrthreads set be checked later. A subsequent patch will improve the ordering. Signed-off-by: NeilBrown Signed-off-by: Chuck Lever

NFSD: handle errors better in write_ports_addfd()

2021-12-13T18:42:49+00:00

If write_ports_add() fails, we shouldn't destroy the serv, unless we had only just created it. So if there are any permanent sockets already attached, leave the serv in place. Signed-off-by: NeilBrown Signed-off-by: Chuck Lever

nfsd: Fix nsfd startup race (again)

2021-12-10T16:54:59+00:00

Commit bd5ae9288d64 ("nfsd: register pernet ops last, unregister first") has re-opened rpc_pipefs_event() race against nfsd_net_id registration (register_pernet_subsys()) which has been fixed by commit bb7ffbf29e76 ("nfsd: fix nsfd startup race triggering BUG_ON"). Restore the order of register_pernet_subsys() vs register_cld_notifier(). Add WARN_ON() to prevent a future regression. Crash info: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000012 CPU: 8 PID: 345 Comm: mount Not tainted 5.4.144-... #1 pc : rpc_pipefs_event+0x54/0x120 [nfsd] lr : rpc_pipefs_event+0x48/0x120 [nfsd] Call trace: rpc_pipefs_event+0x54/0x120 [nfsd] blocking_notifier_call_chain rpc_fill_super get_tree_keyed rpc_fs_get_tree vfs_get_tree do_mount ksys_mount __arm64_sys_mount el0_svc_handler el0_svc Fixes: bd5ae9288d64 ("nfsd: register pernet ops last, unregister first") Cc: stable@vger.kernel.org Signed-off-by: Alexander Sverdlin Signed-off-by: J. Bruce Fields

Merge tag 'nfsd-5.16' of git://linux-nfs.org/~bfields/linux

2021-11-11T00:45:54+00:00

Pull nfsd updates from Bruce Fields: "A slow cycle for nfsd: mainly cleanup, including Neil's patch dropping support for a filehandle format deprecated 20 years ago, and further xdr-related cleanup from Chuck" * tag 'nfsd-5.16' of git://linux-nfs.org/~bfields/linux: (26 commits) nfsd4: remove obselete comment nfsd: document server-to-server-copy parameters NFSD:fix boolreturn.cocci warning nfsd: update create verifier comment SUNRPC: Change return value type of .pc_encode SUNRPC: Replace the "__be32 *p" parameter to .pc_encode NFSD: Save location of NFSv4 COMPOUND status SUNRPC: Change return value type of .pc_decode SUNRPC: Replace the "__be32 *p" parameter to .pc_decode SUNRPC: De-duplicate .pc_release() call sites SUNRPC: Simplify the SVC dispatch code path SUNRPC: Capture value of xdr_buf::page_base SUNRPC: Add trace event when alloc_pages_bulk() makes no progress svcrdma: Split svcrmda_wc_{read,write} tracepoints svcrdma: Split the svcrdma_wc_send() tracepoint svcrdma: Split the svcrdma_wc_receive() tracepoint NFSD: Have legacy NFSD WRITE decoders use xdr_stream_subsegment() SUNRPC: xdr_stream_subsegment() must handle non-zero page_bases NFSD: Initialize pointer ni with NULL and not plain integer 0 NFSD: simplify struct nfsfh ...

NFSD: Keep existing listeners on portlist error

2021-10-06T17:24:25+00:00

If nfsd has existing listening sockets without any processes, then an error returned from svc_create_xprt() for an additional transport will remove those existing listeners. We're seeing this in practice when userspace attempts to create rpcrdma transports without having the rpcrdma modules present before creating nfsd kernel processes. Fix this by checking for existing sockets before calling nfsd_destroy(). Signed-off-by: Benjamin Coddington Signed-off-by: Chuck Lever

NFSD: simplify struct nfsfh

2021-10-02T19:51:10+00:00

Most of the fields in 'struct knfsd_fh' are 2 levels deep (a union and a struct) and are accessed using macros like: #define fh_FOO fh_base.fh_new.fb_FOO This patch makes the union and struct anonymous, so that "fh_FOO" can be a name directly within 'struct knfsd_fh' and the #defines aren't needed. The file handle as a whole is sometimes accessed as "fh_base" or "fh_base.fh_pad", neither of which are particularly helpful names. As the struct holding the filehandle is now anonymous, we cannot use the name of that, so we union it with 'fh_raw' and use that where the raw filehandle is needed. fh_raw also ensure the structure is large enough for the largest possible filehandle. fh_raw is a 'char' array, removing any need to cast it for memcpy etc. SVCFH_fmt() is simplified using the "%ph" printk format. This changes the appearance of filehandles in dprintk() debugging, making them a little more precise. Reviewed-by: Christoph Hellwig Signed-off-by: NeilBrown Signed-off-by: J. Bruce Fields

nfsd: fix error handling of register_pernet_subsys() in init_nfsd()

2021-09-30T14:58:52+00:00

init_nfsd() should not unregister pernet subsys if the register fails but should instead unwind from the last successful operation which is register_filesystem(). Unregistering a failed register_pernet_subsys() call can result in a kernel GPF as revealed by programmatically injecting an error in register_pernet_subsys(). Verified the fix handled failure gracefully with no lingering nfsd entry in /proc/filesystems. This change was introduced by the commit bd5ae9288d64 ("nfsd: register pernet ops last, unregister first"), the original error handling logic was correct. Fixes: bd5ae9288d64 ("nfsd: register pernet ops last, unregister first") Cc: stable@vger.kernel.org Signed-off-by: Patrick Ho Acked-by: J. Bruce Fields Signed-off-by: Chuck Lever