- support asynchronous operation -- add a per-fs 'reserved_space' count, let each outstanding write reserve the _maximum_ amount of physical space it could take. Let GC flush the outstanding writes because the reservations will necessarily be pessimistic. With this we could even do shared writable mmap, if we can have a fs hook for do_wp_page() to make the reservation. - disable compression in commit_write()? - fine-tune the allocation / GC thresholds - chattr support - turning on/off and tuning compression per-inode - checkpointing (do we need this? scan is quite fast) - make the scan code populate real inodes so read_inode just after mount doesn't have to read the flash twice for large files. Make this a per-inode option, changeable with chattr, so you can decide which inodes should be in-core immediately after mount. - test, test, test - NAND flash support: - almost done :) - use bad block check instead of the hardwired byte check - Optimisations: - Split writes so they go to two separate blocks rather than just c->nextblock. By writing _new_ nodes to one block, and garbage-collected REF_PRISTINE nodes to a different one, we can separate clean nodes from those which are likely to become dirty, and end up with blocks which are each far closer to 100% or 0% clean, hence speeding up later GC progress dramatically. - Stop keeping name in-core with struct jffs2_full_dirent. If we keep the hash in the full dirent, we only need to go to the flash in lookup() when we think we've got a match, and in readdir(). - Doubly-linked next_in_ino list to allow us to free obsoleted raw_node_refs immediately? - Remove size from jffs2_raw_node_frag. dedekind: 1. __jffs2_flush_wbuf() has a strange 'pad' parameter. Eliminate. 2. get_sb()->build_fs()->scan() path... Why get_sb() removes scan()'s crap in case of failure? scan() does not clean everything. Fix. /cgit.cgi/linux/net-next.git/commit/include/drm/drm_property.h?id=966d2b04e070bc040319aaebfec09e0144dc3341'>commitdiff
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authorDouglas Miller <dougmill@linux.vnet.ibm.com>2017-01-28 06:42:20 -0600
committerTejun Heo <tj@kernel.org>2017-01-28 07:49:42 -0500
commit966d2b04e070bc040319aaebfec09e0144dc3341 (patch)
tree4b96156e3d1dd4dfd6039b7c219c9dc4616da52d /include/drm/drm_property.h
parent1b1bc42c1692e9b62756323c675a44cb1a1f9dbd (diff)
percpu-refcount: fix reference leak during percpu-atomic transition
percpu_ref_tryget() and percpu_ref_tryget_live() should return "true" IFF they acquire a reference. But the return value from atomic_long_inc_not_zero() is a long and may have high bits set, e.g. PERCPU_COUNT_BIAS, and the return value of the tryget routines is bool so the reference may actually be acquired but the routines return "false" which results in a reference leak since the caller assumes it does not need to do a corresponding percpu_ref_put(). This was seen when performing CPU hotplug during I/O, as hangs in blk_mq_freeze_queue_wait where percpu_ref_kill (blk_mq_freeze_queue_start) raced with percpu_ref_tryget (blk_mq_timeout_work). Sample stack trace: __switch_to+0x2c0/0x450 __schedule+0x2f8/0x970 schedule+0x48/0xc0 blk_mq_freeze_queue_wait+0x94/0x120 blk_mq_queue_reinit_work+0xb8/0x180 blk_mq_queue_reinit_prepare+0x84/0xa0 cpuhp_invoke_callback+0x17c/0x600 cpuhp_up_callbacks+0x58/0x150 _cpu_up+0xf0/0x1c0 do_cpu_up+0x120/0x150 cpu_subsys_online+0x64/0xe0 device_online+0xb4/0x120 online_store+0xb4/0xc0 dev_attr_store+0x68/0xa0 sysfs_kf_write+0x80/0xb0 kernfs_fop_write+0x17c/0x250 __vfs_write+0x6c/0x1e0 vfs_write+0xd0/0x270 SyS_write+0x6c/0x110 system_call+0x38/0xe0 Examination of the queue showed a single reference (no PERCPU_COUNT_BIAS, and __PERCPU_REF_DEAD, __PERCPU_REF_ATOMIC set) and no requests. However, conditions at the time of the race are count of PERCPU_COUNT_BIAS + 0 and __PERCPU_REF_DEAD and __PERCPU_REF_ATOMIC set. The fix is to make the tryget routines use an actual boolean internally instead of the atomic long result truncated to a int. Fixes: e625305b3907 percpu-refcount: make percpu_ref based on longs instead of ints Link: https://bugzilla.kernel.org/show_bug.cgi?id=190751 Signed-off-by: Douglas Miller <dougmill@linux.vnet.ibm.com> Reviewed-by: Jens Axboe <axboe@fb.com> Signed-off-by: Tejun Heo <tj@kernel.org> Fixes: e625305b3907 ("percpu-refcount: make percpu_ref based on longs instead of ints") Cc: stable@vger.kernel.org # v3.18+
Diffstat (limited to 'include/drm/drm_property.h')