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2018-01-24lockd: Fix server refcountingTrond Myklebust1-3/+5
The server shouldn't actually delete the struct nlm_host until it hits the garbage collector. In order to make that work correctly with the refcount API, we can bump the refcount by one, and then use refcount_dec_if_one() in the garbage collector. Signed-off-by: Trond Myklebust <trondmy@gmail.com> Acked-by: J. Bruce Fields <bfields@fieldses.org>
2018-01-23Merge tag 'nfs-rdma-for-4.16-1' of ↵Trond Myklebust14-657/+1662
git://git.linux-nfs.org/projects/anna/linux-nfs NFS-over-RDMA client updates for Linux 4.16 New features: - xprtrdma tracepoints Bugfixes and cleanups: - Fix memory leak if rpcrdma_buffer_create() fails - Fix allocating extra rpcrdma_reps for the backchannel - Remove various unused and redundant variables and lock cycles - Fix IPv6 support in xprt_rdma_set_port() - Fix memory leak by calling buf_free for callback replies - Fix "bytes registered" accounting - Fix kernel-doc comments - SUNRPC tracepoint cleanups for consistent information - Optimizations for __rpc_execute()
2018-01-23SUNRPC: Fix null rpc_clnt dereference in rpc_task_queued tracepointBenjamin Coddington1-2/+2
Backchannel tasks will not have a reference to the rpc_clnt. Return -1 for cl_clid in that case. Signed-off-by: Benjamin Coddington <bcodding@redhat.com> Signed-off-by: Trond Myklebust <trondmy@gmail.com>
2018-01-23SUNRPC: Micro-optimize __rpc_executeChuck Lever1-13/+11
The common case: There are 13 to 14 actions per RPC, and tk_callback is non-NULL in only one of them. There's no need to store a NULL in the tk_callback field during each FSM step. This slightly improves throughput results in dbench and other multi- threaded benchmarks on my two-socket client on 56Gb InfiniBand, but will probably be inconsequential on slower systems. Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2018-01-23SUNRPC: task_run_action should display tk_callbackChuck Lever1-1/+1
This shows up in every RPC: kworker/4:1-19772 [004] 3467.373443: rpc_task_run_action: task:4711@2 flags=0e81 state=0005 status=0 action=call_status kworker/4:1-19772 [004] 3467.373444: rpc_task_run_action: task:4711@2 flags=0e81 state=0005 status=0 action=call_status What's actually going on is that the first iteration of the RPC scheduler is invoking the function in tk_callback (in this case, xprt_timer), then invoking call_status on the next iteration. Feeding do_action, rather than tk_action, to the "task_run_action" trace point will now always display the correct FSM step. Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2018-01-23sunrpc: Format RPC events consistently for displayChuck Lever1-2/+2
Clean up: Make it easier to use text search when browsing a trace report. Other events use "status=%d". Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2018-01-23SUNRPC: Trace xprt_timer eventsChuck Lever3-3/+5
Track RPC timeouts: report the XID and the server address to match the content of network capture. Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2018-01-23xprtrdma: Correct some documenting commentsChuck Lever2-2/+2
Fix kernel-doc warnings in net/sunrpc/xprtrdma/ . net/sunrpc/xprtrdma/verbs.c:1575: warning: No description found for parameter 'count' net/sunrpc/xprtrdma/verbs.c:1575: warning: Excess function parameter 'min_reqs' description in 'rpcrdma_ep_post_extra_recv' net/sunrpc/xprtrdma/backchannel.c:288: warning: No description found for parameter 'r_xprt' net/sunrpc/xprtrdma/backchannel.c:288: warning: Excess function parameter 'xprt' description in 'rpcrdma_bc_receive_call' Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2018-01-23xprtrdma: Fix "bytes registered" accountingChuck Lever1-2/+2
The contents of seg->mr_len changed when ->ro_map stopped returning the full chunk length in the first segment. Count the full length of each Write chunk, not the length of the first segment (which now can only be as large as a page). Fixes: 9d6b04097882 ("xprtrdma: Place registered MWs on a ... ") Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2018-01-23xprtrdma: Instrument allocation/release of rpcrdma_req/rep objectsChuck Lever3-9/+74
Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2018-01-23xprtrdma: Add trace points to instrument QP and CQ access upcallsChuck Lever2-0/+34
Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2018-01-23xprtrdma: Add trace points in the client-side backchannel code pathsChuck Lever3-5/+73
Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2018-01-23xprtrdma: Add trace points for connect eventsChuck Lever3-28/+92
Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2018-01-23xprtrdma: Add trace points to instrument MR allocation and recoveryChuck Lever2-3/+60
Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2018-01-23xprtrdma: Add trace points to instrument memory invalidationChuck Lever4-16/+57
Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2018-01-23xprtrdma: Add trace points in reply decoder pathChuck Lever2-20/+102
This includes decoding Write and Reply chunks, and fixing up inline payloads. Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2018-01-23xprtrdma: Add trace points to instrument memory registrationChuck Lever3-22/+163
Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2018-01-23xprtrdma: Add trace points in the RPC Reply handler pathsChuck Lever3-19/+171
Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2018-01-23xprtrdma: Add trace points in RPC Call transmit pathsChuck Lever3-15/+129
Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2018-01-23rpcrdma: infrastructure for static trace points in rpcrdma.koChuck Lever3-5/+25
Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2018-01-23rdma/ib: Add trace point macros to display human-readable valuesChuck Lever1-0/+129
These can be shared with all kernel ULPs, and more can easily be added as needed. Note: checkpatch.pl has some heartburn with the TRACE_DEFINE_ENUM macros and the LIST macros. These follow the same style as other header files under include/tracing/events , thus should be considered acceptable exceptions. Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Acked-by: Jason Gunthorpe <jgg@mellanox.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2018-01-22NFS: reject request for id_legacy key without auxdataEric Biggers1-1/+5
nfs_idmap_legacy_upcall() is supposed to be called with 'aux' pointing to a 'struct idmap', via the call to request_key_with_auxdata() in nfs_idmap_request_key(). However it can also be reached via the request_key() system call in which case 'aux' will be NULL, causing a NULL pointer dereference in nfs_idmap_prepare_pipe_upcall(), assuming that the key description is valid enough to get that far. Fix this by making nfs_idmap_legacy_upcall() negate the key if no auxdata is provided. As usual, this bug was found by syzkaller. A simple reproducer using the command-line keyctl program is: keyctl request2 id_legacy uid:0 '' @s Fixes: 57e62324e469 ("NFS: Store the legacy idmapper result in the keyring") Reported-by: syzbot+5dfdbcf7b3eb5912abbb@syzkaller.appspotmail.com Cc: <stable@vger.kernel.org> # v3.4+ Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Trond Myklebust <trondmy@gmail.com>
2018-01-18nfs: Do not convert nfs_idmap_cache_timeout to jiffiesJan Chochol1-1/+1
Since commit 57e62324e469 ("NFS: Store the legacy idmapper result in the keyring") nfs_idmap_cache_timeout changed units from jiffies to seconds. Unfortunately sysctl interface was not updated accordingly. As a effect updating /proc/sys/fs/nfs/idmap_cache_timeout with some value will incorrectly multiply this value by HZ. Also reading /proc/sys/fs/nfs/idmap_cache_timeout will show real value divided by HZ. Fixes: 57e62324e469 ("NFS: Store the legacy idmapper result in the keyring") Signed-off-by: Jan Chochol <jan@chochol.info> Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2018-01-18nfs: Use proper enum definitions for nfs_show_stableChuck Lever1-11/+11
Commit 8224b2734ab1 ("NFS: Add static NFS I/O tracepoints") had a hack to work around some odd behavior observed with __print_symbolic. I couldn't ever get it to display NFS_FILE_SYNC when using TRACE_DEFINE_ENUM macros to set up the enum values. I tracked down the actual bug that forced me to add the workaround. That issue will be addressed soon, so replace the hack with a proper implementation. Fixes: 8224b2734ab1 ("NFS: Add static NFS I/O tracepoints") Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2018-01-18nfs41: do not return ENOMEM on LAYOUTUNAVAILABLETigran Mkrtchyan1-3/+1
A pNFS server may return LAYOUTUNAVAILABLE error on LAYOUTGET for files which don't have any layout. In this situation pnfs_update_layout currently returns NULL. As this NULL is converted into ENOMEM, IO requests fails instead of falling back to MDS. Do not return ENOMEM on LAYOUTUNAVAILABLE and let client retry through MDS. Fixes 8d40b0f14846f. I will suggest to backport this fix to affected stable branches. Signed-off-by: Tigran Mkrtchyan <tigran.mkrtchyan@desy.de> [trondmy: Use IS_ERR_OR_NULL()] Fixes: 8d40b0f14846 ("NFS filelayout:call GETDEVICEINFO after...") Cc: stable@vger.kernel.org # v4.11+ Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2018-01-16xprtrdma: Introduce rpcrdma_mw_unmap_and_putChuck Lever4-23/+33
Clean up: Code review suggested that a common bit of code can be placed into a helper function, and this gives us fewer places to stick an "I DMA unmapped something" trace point. Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2018-01-16xprtrdma: Remove usage of "mw"Chuck Lever5-278/+292
Clean up: struct rpcrdma_mw was named after Memory Windows, but xprtrdma no longer supports a Memory Window registration mode. Rename rpcrdma_mw and its fields to reduce confusion and make the code more sensible to read. Renaming "mw" was suggested by Tom Talpey, the author of the original xprtrdma implementation. It's a good idea, but I haven't done this until now because it's a huge diffstat for no benefit other than code readability. However, I'm about to introduce static trace points that expose a few of xprtrdma's internal data structures. They should make sense in the trace report, and it's reasonable to treat trace points as a kernel API contract which might be difficult to change later. While I'm churning things up, two additional changes: - rename variables unhelpfully called "r" to "mr", to improve code clarity, and - rename the MR-related helper functions using the form "rpcrdma_mr_<verb>", to be consistent with other areas of the code. Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2018-01-16xprtrdma: Replace all usage of "frmr" with "frwr"Chuck Lever5-100/+100
Clean up: Over time, the industry has adopted the term "frwr" instead of "frmr". The term "frwr" is now more widely recognized. For the past couple of years I've attempted to add new code using "frwr" , but there still remains plenty of older code that still uses "frmr". Replace all usage of "frmr" to avoid confusion. While we're churning code, rename variables unhelpfully called "f" to "frwr", to improve code clarity. Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2018-01-16xprtrdma: Don't clear RPC_BC_PA_IN_USE on pre-allocated rpc_rqst'sChuck Lever1-6/+1
No need for the overhead of atomically setting and clearing this bit flag for every use of a pre-allocated backchannel rpc_rqst. These are a distinct pool of rpc_rqsts that are used only for callback operations, so it is safe to simply leave the bit set. Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2018-01-16xprtrdma: Split xprt_rdma_send_requestChuck Lever4-32/+50
Clean up. @rqst is set up differently for backchannel Replies. For example, rqst->rq_task and task->tk_client are both NULL. So it is easier to understand and maintain this code path if it is separated. Also, we can get rid of the confusing rl_connect_cookie hack in rpcrdma_bc_receive_call. Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2018-01-16xprtrdma: buf_free not called for CB repliesChuck Lever3-6/+1
Since commit 5a6d1db45569 ("SUNRPC: Add a transport-specific private field in rpc_rqst"), the rpc_rqst's for RPC-over-RDMA backchannel operations leave rq_buffer set to NULL. xprt_release does not invoke ->op->buf_free when rq_buffer is NULL. The RPCRDMA_REQ_F_BACKCHANNEL check in xprt_rdma_free is therefore redundant because xprt_rdma_free is not invoked for backchannel requests. Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2018-01-16xprtrdma: Move unmap-safe logic to rpcrdma_marshal_reqChuck Lever2-5/+11
Clean up. This logic is related to marshaling the request, and I'd like to keep everything that touches req->rl_registered close together, for CPU cache efficiency. Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2018-01-16xprtrdma: Support IPv6 in xprt_rdma_set_portChuck Lever1-4/+24
Clean up a harmless oversight. xprtrdma's ->set_port method has never properly supported IPv6. This issue has never been a problem because NFS/RDMA mounts have always required "port=20049", thus so far, rpcbind is not invoked for these mounts. Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2018-01-16xprtrdma: Remove another sockaddr_storage field (cdata::addr)Chuck Lever3-19/+12
Save more space in struct rpcrdma_xprt by removing the redundant "addr" field from struct rpcrdma_create_data_internal. Wherever we have rpcrdma_xprt, we also have the rpc_xprt, which has a sockaddr_storage field with the same content. Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2018-01-16xprtrdma: Initialize the xprt address string array earlierChuck Lever3-13/+21
This makes the address strings available for debugging messages in earlier stages of transport set up. The first benefit is to get rid of the single-use rep_remote_addr field, saving 128+ bytes in struct rpcrdma_ep. Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2018-01-16xprtrdma: Remove unused padding variablesChuck Lever2-7/+3
Clean up. Remove fields that should have been removed by commit b3221d6a53c4 ("xprtrdma: Remove logic that constructs RDMA_MSGP type calls"). Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2018-01-16xprtrdma: Remove ri_reminv_expectedChuck Lever2-3/+0
Clean up. Commit b5f0afbea4f2 ("xprtrdma: Per-connection pad optimization") should have removed this. Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2018-01-16xprtrdma: Per-mode handling for Remote InvalidationChuck Lever4-30/+27
Refactoring change: Remote Invalidation is particular to the memory registration mode that is use. Use a callout instead of a generic function to handle Remote Invalidation. This gets rid of the 8-byte flags field in struct rpcrdma_mw, of which only a single bit flag has been allocated. Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2018-01-16xprtrdma: Eliminate unnecessary lock cycle in xprt_rdma_send_requestChuck Lever1-1/+1
The rpcrdma_req is not shared yet, and its associated Send hasn't been posted, thus RMW should be safe. There's no need for the expense of a lock cycle here. Fixes: 0ba6f37012db ("xprtrdma: Refactor rpcrdma_deferred_completion") Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2018-01-16xprtrdma: Fix backchannel allocation of extra rpcrdma_repsChuck Lever3-24/+22
The backchannel code uses rpcrdma_recv_buffer_put to add new reps to the free rep list. This also decrements rb_recv_count, which spoofs the receive overrun logic in rpcrdma_buffer_get_rep. Commit 9b06688bc3b9 ("xprtrdma: Fix additional uses of spin_lock_irqsave(rb_lock)") replaced the original open-coded list_add with a call to rpcrdma_recv_buffer_put(), but then a year later, commit 05c974669ece ("xprtrdma: Fix receive buffer accounting") added rep accounting to rpcrdma_recv_buffer_put. It was an oversight to let the backchannel continue to use this function. The fix this, let's combine the "add to free list" logic with rpcrdma_create_rep. Also, do not allocate RPCRDMA_MAX_BC_REQUESTS rpcrdma_reps in rpcrdma_buffer_create and then allocate additional rpcrdma_reps in rpcrdma_bc_setup_reps. Allocating the extra reps during backchannel set-up is sufficient. Fixes: 05c974669ece ("xprtrdma: Fix receive buffer accounting") Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2018-01-16xprtrdma: Fix buffer leak after transport set up failureChuck Lever1-11/+2
This leak has been around forever, and is exceptionally rare. EINVAL causes mount to fail with "an incorrect mount option was specified" although it's not likely that one of the mount options is incorrect. Instead, return ENODEV in this case, as this appears to be an issue with system or device configuration rather than a specific mount option. Some obsolete comments are also removed. Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
2018-01-16NFS: commit direct writes even if they fail partiallyJ. Bruce Fields1-3/+1
If some of the WRITE calls making up an O_DIRECT write syscall fail, we neglect to commit, even if some of the WRITEs succeed. We also depend on the commit code to free the reference count on the nfs_page taken in the "if (request_commit)" case at the end of nfs_direct_write_completion(). The problem was originally noticed because ENOSPC's encountered partway through a write would result in a closed file being sillyrenamed when it should have been unlinked. Signed-off-by: J. Bruce Fields <bfields@redhat.com> Cc: stable@vger.kernel.org Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2018-01-16nfs: remove unused label in nfs_encode_fh()Arnd Bergmann1-1/+0
The only reference to the label got removed, so we now get a harmless compiler warning: fs/nfs/export.c: In function 'nfs_encode_fh': fs/nfs/export.c:58:1: error: label 'out' defined but not used [-Werror=unused-label] Fixes: aaa150089465 ("nfs: remove dead code from nfs_encode_fh()") Signed-off-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2018-01-14SUNRPC: Add explicit rescheduling points in the receive pathTrond Myklebust1-2/+19
When reading the reply from the server, insert an explicit cond_resched() to avoid starving higher priority tasks. Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2018-01-14SUNRPC: Chunk reading of replies from the serverTrond Myklebust1-4/+11
Read the TCP data in chunks of max 2MB so that we do not hog the socket lock. Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2018-01-14SUNRPC: Remove rpc_protocol()Chuck Lever2-17/+0
Since nfs4_create_referral_server was the only call site of rpc_protocol, rpc_protocol can now be removed. Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2018-01-14nfs: Update server port after referral or migrationChuck Lever1-0/+1
After traversing a referral or recovering from a migration event, ensure that the server port reported in /proc/mounts is updated to the correct port setting for the new submount. Reported-by: Helen Chao <helen.chao@oracle.com> Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2018-01-14nfs: Referrals should use the same proto setting as their parentChuck Lever2-5/+20
Helen Chao <helen.chao@oracle.com> noticed that when a user traverses a referral on an NFS/RDMA mount, the resulting submount always uses TCP. This behavior does not match the vers= setting when traversing a referral (vers=4.1 is preserved). It also does not match the behavior of crossing from the pseudofs into a real filesystem (proto=rdma is preserved in that case). The Linux NFS client does not currently support the fs_locations_info attribute. The situation is similar for all NFSv4 servers I know of. Therefore until the community has broad support for fs_locations_info, when following a referral: - First try to connect with RPC-over-RDMA. This will fail quickly if the client has no RDMA-capable interfaces. - If connecting with RPC-over-RDMA fails, or the RPC-over-RDMA transport is not available, use TCP. Reported-by: Helen Chao <helen.chao@oracle.com> Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2018-01-14nfs: Define NFS_RDMA_PORTChuck Lever1-0/+1
The NFS/RDMA port assignment is specified in Section 9 of RFC 8267. Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
2018-01-14lockd: convert nlm_rqst.a_count from atomic_t to refcount_tElena Reshetova3-6/+6
atomic_t variables are currently used to implement reference counters with the following properties: - counter is initialized to 1 using atomic_set() - a resource is freed upon counter reaching zero - once counter reaches zero, its further increments aren't allowed - counter schema uses basic atomic operations (set, inc, inc_not_zero, dec_and_test, etc.) Such atomic variables should be converted to a newly provided refcount_t type and API that prevents accidental counter overflows and underflows. This is important since overflows and underflows can lead to use-after-free situation and be exploitable. The variable nlm_rqst.a_count is used as pure reference counter. Convert it to refcount_t and fix up the operations. **Important note for maintainers: Some functions from refcount_t API defined in lib/refcount.c have different memory ordering guarantees than their atomic counterparts. The full comparison can be seen in https://lkml.org/lkml/2017/11/15/57 and it is hopefully soon in state to be merged to the documentation tree. Normally the differences should not matter since refcount_t provides enough guarantees to satisfy the refcounting use cases, but in some rare cases it might matter. Please double check that you don't have some undocumented memory guarantees for this variable usage. For the nlm_rqst.a_count it might make a difference in following places: - nlmclnt_release_call() and nlmsvc_release_call(): decrement in refcount_dec_and_test() only provides RELEASE ordering and control dependency on success vs. fully ordered atomic counterpart Suggested-by: Kees Cook <keescook@chromium.org> Reviewed-by: David Windsor <dwindsor@gmail.com> Reviewed-by: Hans Liljestrand <ishkamiel@gmail.com> Signed-off-by: Elena Reshetova <elena.reshetova@intel.com> Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
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