- 06 Jan, 2009 40 commits
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Hugh Dickins authored
An unfortunate feature of the Unevictable LRU work was that reclaiming an anonymous page involved an extra scan through the anon_vma: to check that the page is evictable before allocating swap, because the swap could not be freed reliably soon afterwards. Now try_to_free_swap() has replaced remove_exclusive_swap_page(), that's not an issue any more: remove try_to_munlock() call from shrink_page_list(), leaving it to try_to_munmap() to discover if the page is one to be culled to the unevictable list - in which case then try_to_free_swap(). Update unevictable-lru.txt to remove comments on the try_to_munlock() in shrink_page_list(), and shorten some lines over 80 columns. Signed-off-by:
Hugh Dickins <hugh@veritas.com> Cc: Lee Schermerhorn <lee.schermerhorn@hp.com> Acked-by:
Rik van Riel <riel@redhat.com> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Robin Holt <holt@sgi.com> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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Hugh Dickins authored
There's a possible race in try_to_unuse() which Nick Piggin led me to two years ago. Where it does lock_page() after read_swap_cache_async(), what if another task removed that page from swapcache just before we locked it? It would sail though the (*swap_map > 1) tests doing nothing (because it could not have been removed from swapcache before its swap references were gone), until it reaches the delete_from_swap_cache(page) near the bottom. Now imagine that this page has been allocated to swap on a different swap area while we dropped page lock (perhaps at the top, perhaps in unuse_mm): we could wrongly remove from swap cache before the page has been written to swap, so a subsequent do_swap_page() would read in stale data from swap. I think this case could not happen before: remove_exclusive_swap_page() refused while page count was raised. But now with reuse_swap_page() and try_to_free_swap() removing from swap cache without minding page count, I think it could happen - the previous patch argued that it was safe because try_to_unuse() already ignored page count, but overlooked that it might be breaking the assumptions in try_to_unuse() itself. Signed-off-by:
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Hugh Dickins authored
remove_exclusive_swap_page(): its problem is in living up to its name. It doesn't matter if someone else has a reference to the page (raised page_count); it doesn't matter if the page is mapped into userspace (raised page_mapcount - though that hints it may be worth keeping the swap): all that matters is that there be no more references to the swap (and no writeback in progress). swapoff (try_to_unuse) has been removing pages from swapcache for years, with no concern for page count or page mapcount, and we used to have a comment in lookup_swap_cache() recognizing that: if you go for a page of swapcache, you'll get the right page, but it could have been removed from swapcache by the time you get page lock. So, give up asking for exclusivity: get rid of remove_exclusive_swap_page(), and remove_exclusive_swap_page_ref() and remove_exclusive_swap_page_count() which were spawned for the recent LRU work: replace them by the simpler try_to_free_swap() which just checks page_swapcount(). Similarly, remove the page_count limitation from free_swap_and_count(), but assume that it's worth holding on to the swap if page is mapped and swap nowhere near full. Add a vm_swap_full() test in free_swap_cache()? It would be consistent, but I think we probably have enough for now. Signed-off-by:
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Hugh Dickins authored
A good place to free up old swap is where do_wp_page(), or do_swap_page(), is about to redirty the page: the data on disk is then stale and won't be read again; and if we do decide to write the page out later, using the previous swap location makes an unnecessary disk seek very likely. So give can_share_swap_page() the side-effect of delete_from_swap_cache() when it safely can. And can_share_swap_page() was always a misleading name, the more so if it has a side-effect: rename it reuse_swap_page(). Irrelevant cleanup nearby: remove swap_token_default_timeout definition from swap.h: it's used nowhere. Signed-off-by:
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Hugh Dickins authored
An application may rely on get_user_pages() to give it pages writable from userspace and shared with a driver, GUP breaking COW if necessary. It may mprotect() the pages' writability, off and on, from time to time. Normally this works fine (so long as the app does not fork); but just occasionally, under memory pressure, a readonly pte in a newly writable area is COWed unnecessarily, breaking the link with the driver: because do_wp_page() does trylock_page, and falls back to COW whenever that fails. For reliable behaviour in the unshared case, when the trylock_page fails, now unlock pagetable, lock page and relock pagetable, before deciding whether Copy-On-Write is really necessary. Reported-by: Zhou Yingchao Signed-off-by:
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Hugh Dickins authored
do_wp_page()'s VM_FAULT_WRITE return value tells __get_user_pages() that COW has been done if necessary, though it may be leaving the pte without write permission - for the odd case of forced writing to a readonly vma for ptrace. At present GUP then retries the follow_page() without asking for write permission, to escape an endless loop when forced. But an application may be relying on GUP to guarantee a writable page which won't be COWed again when written from userspace, whereas a race here might leave a readonly pte in place? Change the VM_FAULT_WRITE handling to ask follow_page() for write permission again, except in that odd case of forced writing to a readonly vma. Signed-off-by:
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David Rientjes authored
This change introduces two new sysctls to /proc/sys/vm: dirty_background_bytes and dirty_bytes. dirty_background_bytes is the counterpart to dirty_background_ratio and dirty_bytes is the counterpart to dirty_ratio. With growing memory capacities of individual machines, it's no longer sufficient to specify dirty thresholds as a percentage of the amount of dirtyable memory over the entire system. dirty_background_bytes and dirty_bytes specify quantities of memory, in bytes, that represent the dirty limits for the entire system. If either of these values is set, its value represents the amount of dirty memory that is needed to commence either background or direct writeback. When a `bytes' or `ratio' file is written, its counterpart becomes a function of the written value. For example, if dirty_bytes is written to be 8096, 8K of memory is required to commence direct writeback. dirty_ratio is then functionally equivalent to 8K / the amount of dirtyable memory: dirtyable_memory = free pages + mapped pages + file cache dirty_background_bytes = dirty_background_ratio * dirtyable_memory -or- dirty_background_ratio = dirty_background_bytes / dirtyable_memory AND dirty_bytes = dirty_ratio * dirtyable_memory -or- dirty_ratio = dirty_bytes / dirtyable_memory Only one of dirty_background_bytes and dirty_background_ratio may be specified at a time, and only one of dirty_bytes and dirty_ratio may be specified. When one sysctl is written, the other appears as 0 when read. The `bytes' files operate on a page size granularity since dirty limits are compared with ZVC values, which are in page units. Prior to this change, the minimum dirty_ratio was 5 as implemented by get_dirty_limits() although /proc/sys/vm/dirty_ratio would show any user written value between 0 and 100. This restriction is maintained, but dirty_bytes has a lower limit of only one page. Also prior to this change, the dirty_background_ratio could not equal or exceed dirty_ratio. This restriction is maintained in addition to restricting dirty_background_bytes. If either background threshold equals or exceeds that of the dirty threshold, it is implicitly set to half the dirty threshold. Acked-by:
Peter Zijlstra <peterz@infradead.org> Cc: Dave Chinner <david@fromorbit.com> Cc: Christoph Lameter <cl@linux-foundation.org> Signed-off-by:
David Rientjes <rientjes@google.com> Cc: Andrea Righi <righi.andrea@gmail.com> Signed-off-by:
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David Rientjes authored
The background dirty and dirty limits are better defined with type specifiers of unsigned long since negative writeback thresholds are not possible. These values, as returned by get_dirty_limits(), are normally compared with ZVC values to determine whether writeback shall commence or be throttled. Such page counts cannot be negative, so declaring the page limits as signed is unnecessary. Acked-by:
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Julia Lawall authored
As noted by Akinobu Mita in patch b1fceac2, alloc_bootmem and related functions never return NULL and always return a zeroed region of memory. Thus a NULL test or memset after calls to these functions is unnecessary. This was fixed using the following semantic patch. (http://www.emn.fr/x-info/coccinelle/) // <smpl> @@ expression E; statement S; @@ E = \(alloc_bootmem\|alloc_bootmem_low\|alloc_bootmem_pages\|alloc_bootmem_low_pages\|alloc_bootmem_node\|alloc_bootmem_low_pages_node\|alloc_bootmem_pages_node\)(...) ... when != E ( - BUG_ON (E == NULL); | - if (E == NULL) S ) @@ expression E,E1; @@ E = \(alloc_bootmem\|alloc_bootmem_low\|alloc_bootmem_pages\|alloc_bootmem_low_pages\|alloc_bootmem_node\|alloc_bootmem_low_pages_node\|alloc_bootmem_pages_node\)(...) ... when != E - memset(E,0,E1); // </smpl> Signed-off-by:
Julia Lawall <julia@diku.dk> Signed-off-by:
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Hugh Dickins authored
Moving lru_cache_add_active_or_unevictable() into page_add_new_anon_rmap() was good but stupid: we can and should SetPageSwapBacked() there too; and we know for sure that this anonymous, swap-backed page is not file cache. Signed-off-by:
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Hugh Dickins authored
page_lock_anon_vma() and page_unlock_anon_vma() were made available to show_page_path() in vmscan.c; but now that has been removed, make them static in rmap.c again, they're better kept private if possible. Signed-off-by:
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by:
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Hugh Dickins authored
lru_cache_add_active_or_unevictable() and page_add_new_anon_rmap() always appear together. Save some symbol table space and some jumping around by removing lru_cache_add_active_or_unevictable(), folding its code into page_add_new_anon_rmap(): like how we add file pages to lru just after adding them to page cache. Remove the nearby "TODO: is this safe?" comments (yes, it is safe), and change page_add_new_anon_rmap()'s address BUG_ON to VM_BUG_ON as originally intended. Signed-off-by:
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Hugh Dickins authored
The swap code is over-provisioned with BUG_ONs on assorted page flags, mostly dating back to 2.3. They're good documentation, and guard against developer error, but a waste of space on most systems: change them to VM_BUG_ONs, conditional on CONFIG_DEBUG_VM. Just delete the PagePrivate ones: they're later, from 2.5.69, but even less interesting now. Signed-off-by:
Christoph Lameter <cl@linux-foundation.org> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Cc: Mel Gorman <mel@csn.ul.ie> Signed-off-by:
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Hugh Dickins authored
If we add NOOP stubs for SetPageSwapCache() and ClearPageSwapCache(), then we can remove the #ifdef CONFIG_SWAPs from mm/migrate.c. Signed-off-by:
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Hugh Dickins authored
GFP_HIGHUSER_PAGECACHE is just an alias for GFP_HIGHUSER_MOVABLE, making that harder to track down: remove it, and its out-of-work brothers GFP_NOFS_PAGECACHE and GFP_USER_PAGECACHE. Since we're making that improvement to hotremove_migrate_alloc(), I think we can now also remove one of the "o"s from its comment. Signed-off-by:
Mel Gorman <mel@csn.ul.ie> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Signed-off-by:
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Hugh Dickins authored
cgroup_mm_owner_callbacks() was brought in to support the memrlimit controller, but sneaked into mainline ahead of it. That controller has now been shelved, and the mm_owner_changed() args were inadequate for it anyway (they needed an mm pointer instead of a task pointer). Remove the dead code, and restore mm_update_next_owner() locking to how it was before: taking mmap_sem there does nothing for memcontrol.c, now the only user of mm->owner. Signed-off-by:
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Franck Bui-Huu authored
It is known that buffer_mapped() is false in this code path. Signed-off-by:
Franck Bui-Huu <fbuihuu@gmail.com> Signed-off-by:
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Jeremy Fitzhardinge authored
Make the pte-level function in apply_to_range be called in lazy mmu mode, so that any pagetable modifications can be batched. Signed-off-by:
Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Cc: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com> Cc: Hugh Dickins <hugh@veritas.com> Signed-off-by:
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Nick Piggin authored
Lazy unmapping in the vmalloc code has now opened the possibility for use after free bugs to go undetected. We can catch those by forcing an unmap and flush (which is going to be slow, but that's what happens). Signed-off-by:
Nick Piggin <npiggin@suse.de> Signed-off-by:
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Nick Piggin authored
The vmalloc purge lock can be a mutex so we can sleep while a purge is going on (purge involves a global kernel TLB invalidate, so it can take quite a while). Signed-off-by:
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Glauber Costa authored
If we do that, output of files like /proc/vmallocinfo will show things like "vmalloc_32", "vmalloc_user", or whomever the caller was as the caller. This info is not as useful as the real caller of the allocation. So, proposal is to call __vmalloc_node node directly, with matching parameters to save the caller information Signed-off-by:
Glauber Costa <glommer@redhat.com> Signed-off-by:
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Glauber Costa authored
If we can't service a vmalloc allocation, show size of the allocation that actually failed. Useful for debugging. Signed-off-by:
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Johannes Weiner authored
File pages mapped only in sequentially read mappings are perfect reclaim canditates. This patch makes these mappings behave like weak references, their pages will be reclaimed unless they have a strong reference from a normal mapping as well. It changes the reclaim and the unmap path where they check if the page has been referenced. In both cases, accesses through sequentially read mappings will be ignored. Benchmark results from KOSAKI Motohiro: http://marc.info/?l=linux-mm&m=122485301925098&w=2Signed-off-by:Johannes Weiner <hannes@saeurebad.de> Signed-off-by:
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KOSAKI Motohiro authored
#ifdef in *.c file decrease source readability a bit. removing is better. This patch doesn't have any functional change. Signed-off-by:
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KOSAKI Motohiro authored
speculative page references patch (commit: e286781d) removed last pagevec_release_nonlru() caller. So this function can be removed now. This patch doesn't have any functional change. Signed-off-by:
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Yinghai Lu authored
Don't print the size of the zone's memmap array if it does not have one. Impact: cleanup Signed-off-by:
Yinghai Lu <yinghai@kernel.org> Cc: Mel Gorman <mel@csn.ul.ie> Signed-off-by:
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Gary Hade authored
Show node to memory section relationship with symlinks in sysfs Add /sys/devices/system/node/nodeX/memoryY symlinks for all the memory sections located on nodeX. For example: /sys/devices/system/node/node1/memory135 -> ../../memory/memory135 indicates that memory section 135 resides on node1. Also revises documentation to cover this change as well as updating Documentation/ABI/testing/sysfs-devices-memory to include descriptions of memory hotremove files 'phys_device', 'phys_index', and 'state' that were previously not described there. In addition to it always being a good policy to provide users with the maximum possible amount of physical location information for resources that can be hot-added and/or hot-removed, the following are some (but likely not all) of the user benefits provided by this change. Immediate: - Provides information needed to determine the specific node on which a defective DIMM is located. This will reduce system downtime when the node or defective DIMM is swapped out. - Prevents unintended onlining of a memory section that was previously offlined due to a defective DIMM. This could happen during node hot-add when the user or node hot-add assist script onlines _all_ offlined sections due to user or script inability to identify the specific memory sections located on the hot-added node. The consequences of reintroducing the defective memory could be ugly. - Provides information needed to vary the amount and distribution of memory on specific nodes for testing or debugging purposes. Future: - Will provide information needed to identify the memory sections that need to be offlined prior to physical removal of a specific node. Symlink creation during boot was tested on 2-node x86_64, 2-node ppc64, and 2-node ia64 systems. Symlink creation during physical memory hot-add tested on a 2-node x86_64 system. Signed-off-by:Gary Hade <garyhade@us.ibm.com> Signed-off-by:
Badari Pulavarty <pbadari@us.ibm.com> Acked-by:
Ingo Molnar <mingo@elte.hu> Signed-off-by:
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Nick Piggin authored
Chris Mason notices do_sync_mapping_range didn't actually ask for data integrity writeout. Unfortunately, it is advertised as being usable for data integrity operations. This is a data integrity bug. Signed-off-by:
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Andrew Morton authored
Now that we have the early-termination logic in place, it makes sense to bail out early in all other cases where done is set to 1. Signed-off-by:
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Nick Piggin authored
Terminate the write_cache_pages loop upon encountering the first page past end, without locking the page. Pages cannot have their index change when we have a reference on them (truncate, eg truncate_inode_pages_range performs the same check without the page lock). Signed-off-by:
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Nick Piggin authored
In write_cache_pages, if we get stuck behind another process that is cleaning pages, we will be forced to wait for them to finish, then perform our own writeout (if it was redirtied during the long wait), then wait for that. If a page under writeout is still clean, we can skip waiting for it (if we're part of a data integrity sync, we'll be waiting for all writeout pages afterwards, so we'll still be waiting for the other guy's write that's cleaned the page). Signed-off-by:
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Nick Piggin authored
Get rid of some complex expressions from flow control statements, add a comment, remove some duplicate code. Signed-off-by:
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Nick Piggin authored
In write_cache_pages, nr_to_write is heeded even for data-integrity syncs, so the function will return success after writing out nr_to_write pages, even if that was not sufficient to guarantee data integrity. The callers tend to set it to values that could break data interity semantics easily in practice. For example, nr_to_write can be set to mapping->nr_pages * 2, however if a file has a single, dirty page, then fsync is called, subsequent pages might be concurrently added and dirtied, then write_cache_pages might writeout two of these newly dirty pages, while not writing out the old page that should have been written out. Fix this by ignoring nr_to_write if it is a data integrity sync. This is a data integrity bug. The reason this has been done in the past is to avoid stalling sync operations behind page dirtiers. "If a file has one dirty page at offset 1000000000000000 then someone does an fsync() and someone else gets in first and starts madly writing pages at offset 0, we want to write that page at 1000000000000000. Somehow." What we do today is return success after an arbitrary amount of pages are written, whether or not we have provided the data-integrity semantics that the caller has asked for. Even this doesn't actually fix all stall cases completely: in the above situation, if the file has a huge number of pages in pagecache (but not dirty), then mapping->nrpages is going to be huge, even if pages are being dirtied. This change does indeed make the possibility of long stalls lager, and that's not a good thing, but lying about data integrity is even worse. We have to either perform the sync, or return -ELINUXISLAME so at least the caller knows what has happened. There are subsequent competing approaches in the works to solve the stall problems properly, without compromising data integrity. Signed-off-by:
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Nick Piggin authored
In write_cache_pages, if ret signals a real error, but we still have some pages left in the pagevec, done would be set to 1, but the remaining pages would continue to be processed and ret will be overwritten in the process. It could easily be overwritten with success, and thus success will be returned even if there is an error. Thus the caller is told all writes succeeded, wheras in reality some did not. Fix this by bailing immediately if there is an error, and retaining the first error code. This is a data integrity bug. Signed-off-by:
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Nick Piggin authored
We'd like to break out of the loop early in many situations, however the existing code has been setting mapping->writeback_index past the final page in the pagevec lookup for cyclic writeback. This is a problem if we don't process all pages up to the final page. Currently the code mostly keeps writeback_index reasonable and hacked around this by not breaking out of the loop or writing pages outside the range in these cases. Keep track of a real "done index" that enables us to terminate the loop in a much more flexible manner. Needed by the subsequent patch to preserve writepage errors, and then further patches to break out of the loop early for other reasons. However there are no functional changes with this patch alone. Signed-off-by:
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Nick Piggin authored
In write_cache_pages, scanned == 1 is supposed to mean that cyclic writeback has circled through zero, thus we should not circle again. However it gets set to 1 after the first successful pagevec lookup. This leads to cases where not enough data gets written. Counterexample: file with first 10 pages dirty, writeback_index == 5, nr_to_write == 10. Then the 5 last pages will be found, and scanned will be set to 1, after writing those out, we will not cycle back to get the first 5. Rework this logic, now we'll always cycle unless we started off from index 0. When cycling, only write out as far as 1 page before the start page from the first cycle (so we don't write parts of the file twice). Signed-off-by:
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Miquel van Smoorenburg authored
While tracing I/O patterns with blktrace (a great tool) a few weeks ago I identified a minor issue in fs/mpage.c As the comment above mpage_readpages() says, a fs's get_block function will set BH_Boundary when it maps a block just before a block for which extra I/O is required. Since get_block() can map a range of pages, for all these pages the BH_Boundary flag will be set. But we only need to push what I/O we have accumulated at the last block of this range. This makes do_mpage_readpage() send out the largest possible bio instead of a bunch of page-sized ones in the BH_Boundary case. Signed-off-by:
Miquel van Smoorenburg <mikevs@xs4all.net> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Cc: Jens Axboe <jens.axboe@oracle.com> Signed-off-by:
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David Rientjes authored
When cpusets are enabled, it's necessary to print the triggering task's set of allowable nodes so the subsequently printed meminfo can be interpreted correctly. We also print the task's cpuset name for informational purposes. [rientjes@google.com: task lock current before dereferencing cpuset] Cc: Paul Menage <menage@google.com> Cc: Li Zefan <lizf@cn.fujitsu.com> Signed-off-by:
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David Rientjes authored
zone_scan_mutex is actually a spinlock, so name it appropriately. Signed-off-by:
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Nick Piggin authored
Rather than have the pagefault handler kill a process directly if it gets a VM_FAULT_OOM, have it call into the OOM killer. With increasingly sophisticated oom behaviour (cpusets, memory cgroups, oom killing throttling, oom priority adjustment or selective disabling, panic on oom, etc), it's silly to unconditionally kill the faulting process at page fault time. Create a hook for pagefault oom path to call into instead. Only converted x86 and uml so far. [akpm@linux-foundation.org: make __out_of_memory() static] [akpm@linux-foundation.org: fix comment] Signed-off-by:
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