lwn.git/lib/radix-tree.c, branch v2.6.35.1

radix-tree: fix radix_tree_prev_hole() underflow case

2010-05-27T16:12:53+00:00

radix_tree_prev_hole() used LONG_MAX to detect underflow; however, ULONG_MAX is clearly what was intended, both here and by its only user (count_history_pages at mm/readahead.c). Reviewed-by: Wu Fengguang Signed-off-by: Cesar Eduardo Barros Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

radix_tree_tag_get() is not as safe as the docs make out [ver #2]

2010-04-09T17:12:03+00:00

radix_tree_tag_get() is not safe to use concurrently with radix_tree_tag_set() or radix_tree_tag_clear(). The problem is that the double tag_get() in radix_tree_tag_get(): if (!tag_get(node, tag, offset)) saw_unset_tag = 1; if (height == 1) { int ret = tag_get(node, tag, offset); may see the value change due to the action of set/clear. RCU is no protection against this as no pointers are being changed, no nodes are being replaced according to a COW protocol - set/clear alter the node directly. The documentation in linux/radix-tree.h, however, says that radix_tree_tag_get() is an exception to the rule that "any function modifying the tree or tags (...) must exclude other modifications, and exclude any functions reading the tree". The problem is that the next statement in radix_tree_tag_get() checks that the tag doesn't vary over time: BUG_ON(ret && saw_unset_tag); This has been seen happening in FS-Cache: https://www.redhat.com/archives/linux-cachefs/2010-April/msg00013.html To this end, remove the BUG_ON() from radix_tree_tag_get() and note in various comments that the value of the tag may change whilst the RCU read lock is held, and thus that the return value of radix_tree_tag_get() may not be relied upon unless radix_tree_tag_set/clear() and radix_tree_delete() are excluded from running concurrently with it. Reported-by: Romain DEGEZ Signed-off-by: David Howells Acked-by: Nick Piggin Signed-off-by: Linus Torvalds

include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h

2010-03-30T13:02:32+00:00

percpu.h is included by sched.h and module.h and thus ends up being included when building most .c files. percpu.h includes slab.h which in turn includes gfp.h making everything defined by the two files universally available and complicating inclusion dependencies. percpu.h -> slab.h dependency is about to be removed. Prepare for this change by updating users of gfp and slab facilities include those headers directly instead of assuming availability. As this conversion needs to touch large number of source files, the following script is used as the basis of conversion. http://userweb.kernel.org/~tj/misc/slabh-sweep.py The script does the followings. * Scan files for gfp and slab usages and update includes such that only the necessary includes are there. ie. if only gfp is used, gfp.h, if slab is used, slab.h. * When the script inserts a new include, it looks at the include blocks and try to put the new include such that its order conforms to its surrounding. It's put in the include block which contains core kernel includes, in the same order that the rest are ordered - alphabetical, Christmas tree, rev-Xmas-tree or at the end if there doesn't seem to be any matching order. * If the script can't find a place to put a new include (mostly because the file doesn't have fitting include block), it prints out an error message indicating which .h file needs to be added to the file. The conversion was done in the following steps. 1. The initial automatic conversion of all .c files updated slightly over 4000 files, deleting around 700 includes and adding ~480 gfp.h and ~3000 slab.h inclusions. The script emitted errors for ~400 files. 2. Each error was manually checked. Some didn't need the inclusion, some needed manual addition while adding it to implementation .h or embedding .c file was more appropriate for others. This step added inclusions to around 150 files. 3. The script was run again and the output was compared to the edits from #2 to make sure no file was left behind. 4. Several build tests were done and a couple of problems were fixed. e.g. lib/decompress_*.c used malloc/free() wrappers around slab APIs requiring slab.h to be added manually. 5. The script was run on all .h files but without automatically editing them as sprinkling gfp.h and slab.h inclusions around .h files could easily lead to inclusion dependency hell. Most gfp.h inclusion directives were ignored as stuff from gfp.h was usually wildly available and often used in preprocessor macros. Each slab.h inclusion directive was examined and added manually as necessary. 6. percpu.h was updated not to include slab.h. 7. Build test were done on the following configurations and failures were fixed. CONFIG_GCOV_KERNEL was turned off for all tests (as my distributed build env didn't work with gcov compiles) and a few more options had to be turned off depending on archs to make things build (like ipr on powerpc/64 which failed due to missing writeq). * x86 and x86_64 UP and SMP allmodconfig and a custom test config. * powerpc and powerpc64 SMP allmodconfig * sparc and sparc64 SMP allmodconfig * ia64 SMP allmodconfig * s390 SMP allmodconfig * alpha SMP allmodconfig * um on x86_64 SMP allmodconfig 8. percpu.h modifications were reverted so that it could be applied as a separate patch and serve as bisection point. Given the fact that I had only a couple of failures from tests on step 6, I'm fairly confident about the coverage of this conversion patch. If there is a breakage, it's likely to be something in one of the arch headers which should be easily discoverable easily on most builds of the specific arch. Signed-off-by: Tejun Heo Guess-its-ok-by: Christoph Lameter Cc: Ingo Molnar Cc: Lee Schermerhorn

radix-tree: Disable RCU lockdep checking in radix tree

2010-02-25T09:34:50+00:00

Because the radix tree is used with many different locking designs, we cannot do any effective checking without changing the radix-tree APIs. It might make sense to do this later, but only if the RCU lockdep checking proves itself sufficiently valuable. Signed-off-by: Paul E. McKenney Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: mathieu.desnoyers@polymtl.ca Cc: josh@joshtriplett.org Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: Valdis.Kletnieks@vt.edu Cc: dhowells@redhat.com LKML-Reference: <1266887105-1528-10-git-send-email-paulmck@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar

FS-Cache: Don't delete pending pages from the page-store tracking tree

2009-11-19T18:11:29+00:00

Don't delete pending pages from the page-store tracking tree, but rather send them for another write as they've presumably been updated. Signed-off-by: David Howells

FS-Cache: Use radix tree preload correctly in tracking of pages to be stored

2009-11-19T18:11:14+00:00

__fscache_write_page() attempts to load the radix tree preallocation pool for the CPU it is on before calling radix_tree_insert(), as the insertion must be done inside a pair of spinlocks. Use of the preallocation pool, however, is contingent on the radix tree being initialised without __GFP_WAIT specified. __fscache_acquire_cookie() was passing GFP_NOFS to INIT_RADIX_TREE() - but that includes __GFP_WAIT. The solution is to AND out __GFP_WAIT. Additionally, the banner comment to radix_tree_preload() is altered to make note of this prerequisite. Possibly there should be a WARN_ON() too. Without this fix, I have seen the following recursive deadlock caused by radix_tree_insert() attempting to allocate memory inside the spinlocked region, which resulted in FS-Cache being called back into to release memory - which required the spinlock already held. ============================================= [ INFO: possible recursive locking detected ] 2.6.32-rc6-cachefs #24 --------------------------------------------- nfsiod/7916 is trying to acquire lock: (&cookie->lock){+.+.-.}, at: [] __fscache_uncache_page+0xdb/0x160 [fscache] but task is already holding lock: (&cookie->lock){+.+.-.}, at: [] __fscache_write_page+0x15c/0x3f3 [fscache] other info that might help us debug this: 5 locks held by nfsiod/7916: #0: (nfsiod){+.+.+.}, at: [] worker_thread+0x19a/0x2e2 #1: (&task->u.tk_work#2){+.+.+.}, at: [] worker_thread+0x19a/0x2e2 #2: (&cookie->lock){+.+.-.}, at: [] __fscache_write_page+0x15c/0x3f3 [fscache] #3: (&object->lock#2){+.+.-.}, at: [] __fscache_write_page+0x197/0x3f3 [fscache] #4: (&cookie->stores_lock){+.+...}, at: [] __fscache_write_page+0x19f/0x3f3 [fscache] stack backtrace: Pid: 7916, comm: nfsiod Not tainted 2.6.32-rc6-cachefs #24 Call Trace: [] __lock_acquire+0x1649/0x16e3 [] ? __lock_acquire+0x7b7/0x16e3 [] ? dump_trace+0x248/0x257 [] lock_acquire+0x57/0x6d [] ? __fscache_uncache_page+0xdb/0x160 [fscache] [] _spin_lock+0x2c/0x3b [] ? __fscache_uncache_page+0xdb/0x160 [fscache] [] __fscache_uncache_page+0xdb/0x160 [fscache] [] ? __fscache_check_page_write+0x0/0x71 [fscache] [] nfs_fscache_release_page+0x86/0xc4 [nfs] [] nfs_release_page+0x3c/0x41 [nfs] [] try_to_release_page+0x32/0x3b [] shrink_page_list+0x316/0x4ac [] ? mark_held_locks+0x52/0x70 [] ? _spin_unlock_irq+0x2b/0x31 [] shrink_inactive_list+0x392/0x67c [] ? mark_held_locks+0x52/0x70 [] shrink_list+0x8d/0x8f [] shrink_zone+0x278/0x33c [] ? ktime_get_ts+0xad/0xba [] try_to_free_pages+0x22e/0x392 [] ? isolate_pages_global+0x0/0x212 [] __alloc_pages_nodemask+0x3dc/0x5cf [] cache_alloc_refill+0x34d/0x6c1 [] ? radix_tree_node_alloc+0x52/0x5c [] kmem_cache_alloc+0xb2/0x118 [] radix_tree_node_alloc+0x52/0x5c [] radix_tree_insert+0x57/0x19c [] __fscache_write_page+0x1e3/0x3f3 [fscache] [] __nfs_readpage_to_fscache+0x58/0x11e [nfs] [] nfs_readpage_release+0x34/0x9b [nfs] [] nfs_readpage_release_full+0x32/0x4b [nfs] [] rpc_release_calldata+0x12/0x14 [sunrpc] [] rpc_free_task+0x59/0x61 [sunrpc] [] rpc_async_release+0x10/0x12 [sunrpc] [] worker_thread+0x1ef/0x2e2 [] ? worker_thread+0x19a/0x2e2 [] ? thread_return+0x3e/0x101 [] ? rpc_async_release+0x0/0x12 [sunrpc] [] ? autoremove_wake_function+0x0/0x34 [] ? trace_hardirqs_on+0xd/0xf [] ? worker_thread+0x0/0x2e2 [] kthread+0x7a/0x82 [] child_rip+0xa/0x20 [] ? restore_args+0x0/0x30 [] ? add_wait_queue+0x15/0x44 [] ? kthread+0x0/0x82 [] ? child_rip+0x0/0x20 Signed-off-by: David Howells

lib: do code optimization for radix_tree_lookup() and radix_tree_lookup_slot()

2009-06-17T02:47:49+00:00

radix_tree_lookup() and radix_tree_lookup_slot() have much the same code except for the return value. Introduce radix_tree_lookup_element() to do the real work. /* * is_slot == 1 : search for the slot. * is_slot == 0 : search for the node. */ static void * radix_tree_lookup_element(struct radix_tree_root *root, unsigned long index, int is_slot); Signed-off-by: Huang Shijie Cc: Nick Piggin Cc: Christoph Lameter Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

radix-tree: add radix_tree_prev_hole()

2009-06-17T02:47:30+00:00

The counterpart of radix_tree_next_hole(). To be used by context readahead. Signed-off-by: Wu Fengguang Cc: Vladislav Bolkhovitin Cc: Jens Axboe Cc: Jeff Moyer Cc: Nick Piggin Cc: Ying Han Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial

2009-01-07T19:31:52+00:00

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial: (24 commits) trivial: chack -> check typo fix in main Makefile trivial: Add a space (and a comma) to a printk in 8250 driver trivial: Fix misspelling of "firmware" in docs for ncr53c8xx/sym53c8xx trivial: Fix misspelling of "firmware" in powerpc Makefile trivial: Fix misspelling of "firmware" in usb.c trivial: Fix misspelling of "firmware" in qla1280.c trivial: Fix misspelling of "firmware" in a100u2w.c trivial: Fix misspelling of "firmware" in megaraid.c trivial: Fix misspelling of "firmware" in ql4_mbx.c trivial: Fix misspelling of "firmware" in acpi_memhotplug.c trivial: Fix misspelling of "firmware" in ipw2100.c trivial: Fix misspelling of "firmware" in atmel.c trivial: Fix misspelled firmware in Kconfig trivial: fix an -> a typos in documentation and comments trivial: fix then -> than typos in comments and documentation trivial: update Jesper Juhl CREDITS entry with new email trivial: fix singal -> signal typo trivial: Fix incorrect use of "loose" in event.c trivial: printk: fix indentation of new_text_line declaration trivial: rtc-stk17ta8: fix sparse warning ...

lib: radix_tree.c make percpu variable static

2009-01-06T23:59:11+00:00

radix_tree_preloads is unused outside of this file, make it static. Noticed by sparse: lib/radix-tree.c:84:1: warning: symbol 'per_cpu__radix_tree_preloads' was not declared. Should it be static? Signed-off-by: Harvey Harrison Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds