69c7eeb4f6
[ Upstream commit 31b62908693c90d4d07db597e685d9f25a120073 ] I received the following warning while running cthon against an ontap server running pNFS: [ 57.202521] ============================= [ 57.202522] WARNING: suspicious RCU usage [ 57.202523] 6.7.0-rc3-g2cc14f52aeb7 #41492 Not tainted [ 57.202525] ----------------------------- [ 57.202525] net/sunrpc/xprtmultipath.c:349 RCU-list traversed in non-reader section!! [ 57.202527] other info that might help us debug this: [ 57.202528] rcu_scheduler_active = 2, debug_locks = 1 [ 57.202529] no locks held by test5/3567. [ 57.202530] stack backtrace: [ 57.202532] CPU: 0 PID: 3567 Comm: test5 Not tainted 6.7.0-rc3-g2cc14f52aeb7 #41492 5b09971b4965c0aceba19f3eea324a4a806e227e [ 57.202534] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS unknown 2/2/2022 [ 57.202536] Call Trace: [ 57.202537] <TASK> [ 57.202540] dump_stack_lvl+0x77/0xb0 [ 57.202551] lockdep_rcu_suspicious+0x154/0x1a0 [ 57.202556] rpc_xprt_switch_has_addr+0x17c/0x190 [sunrpc ebe02571b9a8ceebf7d98e71675af20c19bdb1f6] [ 57.202596] rpc_clnt_setup_test_and_add_xprt+0x50/0x180 [sunrpc ebe02571b9a8ceebf7d98e71675af20c19bdb1f6] [ 57.202621] ? rpc_clnt_add_xprt+0x254/0x300 [sunrpc ebe02571b9a8ceebf7d98e71675af20c19bdb1f6] [ 57.202646] rpc_clnt_add_xprt+0x27a/0x300 [sunrpc ebe02571b9a8ceebf7d98e71675af20c19bdb1f6] [ 57.202671] ? __pfx_rpc_clnt_setup_test_and_add_xprt+0x10/0x10 [sunrpc ebe02571b9a8ceebf7d98e71675af20c19bdb1f6] [ 57.202696] nfs4_pnfs_ds_connect+0x345/0x760 [nfsv4 c716d88496ded0ea6d289bbea684fa996f9b57a9] [ 57.202728] ? __pfx_nfs4_test_session_trunk+0x10/0x10 [nfsv4 c716d88496ded0ea6d289bbea684fa996f9b57a9] [ 57.202754] nfs4_fl_prepare_ds+0x75/0xc0 [nfs_layout_nfsv41_files e3a4187f18ae8a27b630f9feae6831b584a9360a] [ 57.202760] filelayout_write_pagelist+0x4a/0x200 [nfs_layout_nfsv41_files e3a4187f18ae8a27b630f9feae6831b584a9360a] [ 57.202765] pnfs_generic_pg_writepages+0xbe/0x230 [nfsv4 c716d88496ded0ea6d289bbea684fa996f9b57a9] [ 57.202788] __nfs_pageio_add_request+0x3fd/0x520 [nfs 6c976fa593a7c2976f5a0aeb4965514a828e6902] [ 57.202813] nfs_pageio_add_request+0x18b/0x390 [nfs 6c976fa593a7c2976f5a0aeb4965514a828e6902] [ 57.202831] nfs_do_writepage+0x116/0x1e0 [nfs 6c976fa593a7c2976f5a0aeb4965514a828e6902] [ 57.202849] nfs_writepages_callback+0x13/0x30 [nfs 6c976fa593a7c2976f5a0aeb4965514a828e6902] [ 57.202866] write_cache_pages+0x265/0x450 [ 57.202870] ? __pfx_nfs_writepages_callback+0x10/0x10 [nfs 6c976fa593a7c2976f5a0aeb4965514a828e6902] [ 57.202891] nfs_writepages+0x141/0x230 [nfs 6c976fa593a7c2976f5a0aeb4965514a828e6902] [ 57.202913] do_writepages+0xd2/0x230 [ 57.202917] ? filemap_fdatawrite_wbc+0x5c/0x80 [ 57.202921] filemap_fdatawrite_wbc+0x67/0x80 [ 57.202924] filemap_write_and_wait_range+0xd9/0x170 [ 57.202930] nfs_wb_all+0x49/0x180 [nfs 6c976fa593a7c2976f5a0aeb4965514a828e6902] [ 57.202947] nfs4_file_flush+0x72/0xb0 [nfsv4 c716d88496ded0ea6d289bbea684fa996f9b57a9] [ 57.202969] __se_sys_close+0x46/0xd0 [ 57.202972] do_syscall_64+0x68/0x100 [ 57.202975] ? do_syscall_64+0x77/0x100 [ 57.202976] ? do_syscall_64+0x77/0x100 [ 57.202979] entry_SYSCALL_64_after_hwframe+0x6e/0x76 [ 57.202982] RIP: 0033:0x7fe2b12e4a94 [ 57.202985] Code: 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 80 3d d5 18 0e 00 00 74 13 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 44 c3 0f 1f 00 48 83 ec 18 89 7c 24 0c e8 c3 [ 57.202987] RSP: 002b:00007ffe857ddb38 EFLAGS: 00000202 ORIG_RAX: 0000000000000003 [ 57.202989] RAX: ffffffffffffffda RBX: 00007ffe857dfd68 RCX: 00007fe2b12e4a94 [ 57.202991] RDX: 0000000000002000 RSI: 00007ffe857ddc40 RDI: 0000000000000003 [ 57.202992] RBP: 00007ffe857dfc50 R08: 7fffffffffffffff R09: 0000000065650f49 [ 57.202993] R10: 00007fe2b11f8300 R11: 0000000000000202 R12: 0000000000000000 [ 57.202994] R13: 00007ffe857dfd80 R14: 00007fe2b1445000 R15: 0000000000000000 [ 57.202999] </TASK> The problem seems to be that two out of three callers aren't taking the rcu_read_lock() before calling the list_for_each_entry_rcu() function in rpc_xprt_switch_has_addr(). I fix this by having rpc_xprt_switch_has_addr() unconditionaly take the rcu_read_lock(), which is okay to do recursively in the case that the lock has already been taken by a caller. Reviewed-by: Jeff Layton <jlayton@kernel.org> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
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Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
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https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.