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Ilya Dryomov 0b207d02bd rbd: take header_rwsem in rbd_dev_refresh() only when updating 
rbd_dev_refresh() has been holding header_rwsem across header and
parent info read-in unnecessarily for ages.  With commit 870611e487
("rbd: get snapshot context after exclusive lock is ensured to be
held"), the potential for deadlocks became much more real owning to
a) header_rwsem now nesting inside lock_rwsem and b) rw_semaphores
not allowing new readers after a writer is registered.

For example, assuming that I/O request 1, I/O request 2 and header
read-in request all target the same OSD:

1. I/O request 1 comes in and gets submitted
2. watch error occurs
3. rbd_watch_errcb() takes lock_rwsem for write, clears owner_cid and
   releases lock_rwsem
4. after reestablishing the watch, rbd_reregister_watch() calls
   rbd_dev_refresh() which takes header_rwsem for write and submits
   a header read-in request
5. I/O request 2 comes in: after taking lock_rwsem for read in
   __rbd_img_handle_request(), it blocks trying to take header_rwsem
   for read in rbd_img_object_requests()
6. another watch error occurs
7. rbd_watch_errcb() blocks trying to take lock_rwsem for write
8. I/O request 1 completion is received by the messenger but can't be
   processed because lock_rwsem won't be granted anymore
9. header read-in request completion can't be received, let alone
   processed, because the messenger is stranded

Change rbd_dev_refresh() to take header_rwsem only for actually
updating rbd_dev->header.  Header and parent info read-in don't need
any locking.

Cc: stable@vger.kernel.org # 0b035401c5: rbd: move rbd_dev_refresh() definition
Cc: stable@vger.kernel.org # 510a7330c8: rbd: decouple header read-in from updating rbd_dev->header
Cc: stable@vger.kernel.org # c10311776f: rbd: decouple parent info read-in from updating rbd_dev
Cc: stable@vger.kernel.org
Fixes: 870611e487 ("rbd: get snapshot context after exclusive lock is ensured to be held")
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Dongsheng Yang <dongsheng.yang@easystack.cn>
History 2023-09-26 10:33:19 +02:00
arch Misc fixes: 2023-09-17 11:13:37 -07:00
block blk-mq: fix tags UAF when shrinking q->nr_hw_queues 2023-09-11 16:17:34 -06:00
certs certs: Reference revocation list for all keyrings 2023-08-17 20:12:41 +00:00
crypto This update includes the following changes: 2023-08-29 11:23:29 -07:00
Documentation Driver core fix for 6.6-rc2 2023-09-16 11:26:52 -07:00
drivers rbd: take header_rwsem in rbd_dev_refresh() only when updating 2023-09-26 10:33:19 +02:00
fs ceph: remove unnecessary check for NULL in parse_longname() 2023-09-18 12:04:50 +02:00
include Revert "ceph: make members in struct ceph_mds_request_args_ext a union" 2023-09-18 12:04:50 +02:00
init workqueue: Changes for v6.6 2023-09-01 16:06:32 -07:00
io_uring io_uring/net: fix iter retargeting for selected buf 2023-09-14 10:12:55 -06:00
ipc Add x86 shadow stack support 2023-08-31 12:20:12 -07:00
kernel Fix a performance regression on large SMT systems, an Intel SMT4 2023-09-17 11:10:23 -07:00
lib linux-kselftest-kunit-6.6-rc2 2023-09-12 09:05:49 -07:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm vm: fix move_vma() memory accounting being off 2023-09-16 15:23:31 -07:00
net kcm: Fix error handling for SOCK_DGRAM in kcm_sendmsg(). 2023-09-14 10:43:51 +02:00
rust Documentation work keeps chugging along; stuff for 6.6 includes: 2023-08-30 20:05:42 -07:00
samples VFIO updates for v6.6-rc1 2023-08-30 20:36:01 -07:00
scripts Kbuild fixes for v6.6 2023-09-16 15:27:00 -07:00
security selinux: fix handling of empty opts in selinux_fs_context_submount() 2023-09-12 17:31:08 -04:00
sound sound fixes for 6.6-rc1 2023-09-08 13:07:50 -07:00
tools Fix a cold functions related false-positive objtool warning 2023-09-17 10:59:37 -07:00
usr initramfs: Encode dependency on KBUILD_BUILD_TIMESTAMP 2023-06-06 17:54:49 +09:00
virt ARM: 2023-09-07 13:52:20 -07:00
.clang-format iommu: Add for_each_group_device() 2023-05-23 08:15:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: rpm-pkg: rename binkernel.spec to kernel.spec 2023-07-25 00:59:33 +09:00
.mailmap for-linus-2023083101 2023-09-01 12:31:44 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS USB: Remove Wireless USB and UWB documentation 2023-08-09 14:17:32 +02:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS This pull-request renames the genpd subsystem to pmdomain. 2023-09-13 14:18:19 -07:00
Makefile Linux 6.6-rc2 2023-09-17 14:40:24 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    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.