- 28 Apr, 2008 40 commits
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Harvey Harrison authored
__FUNCTION__ is gcc-specific, use __func__ Signed-off-by:
Harvey Harrison <harvey.harrison@gmail.com> Cc: Jeff Dike <jdike@addtoit.com> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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WANG Cong authored
Make some small improvements for arch/um/kernel/um_arch.c. Signed-off-by:
WANG Cong <xiyou.wangcong@gmail.com> Acked-by:
Jeff Dike <jdike@addtoit.com> Signed-off-by:
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KOSAKI Motohiro authored
add constfy to pgd_offset() for avoid following warnings. CC mm/pagewalk.o mm/pagewalk.c: In function 'walk_page_range': mm/pagewalk.c:111: warning: passing argument 1 of 'pgd_offset' discards qualifiers from p\ ointer target type Signed-off-by:
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Matt Mackall <mpm@selenic.com> Cc: "Vegard Nossum" <vegard.nossum@gmail.com> Cc: Mikael Starvik <starvik@axis.com> Cc: Jesper Nilsson <jesper.nilsson@axis.com> Signed-off-by:
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Johannes Weiner authored
show_mem() has no need to print the amount of free swap space manually because show_free_areas() does this already and is called by the former. The two outputs only differ in text formatting: printk("Free swap = %lukB\n", ...); printk("Free swap: %6ldkB\n", ...); Signed-off-by:Johannes Weiner <hannes@saeurebad.de> Cc: Mikael Starvik <mikael.starvik@axis.com> Signed-off-by:
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Alan Cox authored
Just the modem bits this time Signed-off-by:
Alan Cox <alan@redhat.com> Cc: Mikael Starvik <mikael.starvik@axis.com> Signed-off-by:
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Harvey Harrison authored
__FUNCTION__ is gcc-specific, use __func__ Signed-off-by:
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Johannes Weiner authored
show_mem() has no need to print the amount of free swap space manually because show_free_areas() does this already and is called by the former. The two outputs only differ in text formatting: printk("Free swap = %lukB\n", ...); printk("Free swap: %6ldkB\n", ...); Signed-off-by: -
Andrew Morton authored
Fix things like this: security/selinux/netnode.c: In function 'sel_netnode_find': security/selinux/netnode.c:126: warning: 'idx' may be used uninitialized in this function security/selinux/netnode.c: In function 'sel_netnode_sid': security/selinux/netnode.c:225: warning: 'ret' may be used uninitialized in this function security/selinux/netnode.c:168: warning: 'idx' may be used uninitialized in this function due to code correctly not expecting BUG() to return. For some reason this reduces the object code size for that particular file. Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru> Cc: Richard Henderson <rth@twiddle.net> Signed-off-by:
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S.Caglar Onur authored
The functions time_before, time_before_eq, time_after, and time_after_eq are more robust for comparing jiffies against other values. So implement usage of the time_after() macro, defined in linux/jiffies.h, which deals with wrapping correctly [akpm@linux-foundation.org: fix warning] Signed-off-by:
S.Caglar Onur <caglar@pardus.org.tr> Cc: Richard Henderson <rth@twiddle.net> Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru> Signed-off-by:
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Harvey Harrison authored
Signed-off-by:
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Harvey Harrison authored
__FUNCTION__ is gcc-specific, use __func__ The change in pci-iommu,c should be safe as arena has not been assigned when we get to this point. Some were within #if 0 blocks, have changed them and left the blocks as they appear to be debugging infrastructure. A #define FN __FUNCTION__ was removed and occurances of FN were replaced with __func__ as well. Signed-off-by:
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Jim Meyering authored
arch/alpha/kernel/module.c (module_frob_arch_sections): Handle kcalloc failure. Signed-off-by:
Jim Meyering <meyering@redhat.com> Cc: Richard Henderson <rth@twiddle.net> Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru> Signed-off-by:
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Serge E. Hallyn authored
With the introduction of per-process securebits, the capabilities-related prctl callbacks were moved into cap_task_prctl(). Have smack use cap_task_prctl() so that PR_SET_KEEPCAPS is defined. Signed-off-by:
Serge E. Hallyn <serue@us.ibm.com> Acked-by:
Casey Schaufler <casey@schaufler-ca.com> Signed-off-by:
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Casey Schaufler authored
The functions smk_cipso_doi and smk_unlbl_ambient are not used outside smackfs.c and should hence be static. Signed-off-by:
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Serge E. Hallyn authored
With the introduction of per-process securebits, the capabilities-related prctl callbacks were moved into cap_task_prctl(). Have root_plug use cap_task_prctl() so that PR_SET_KEEPCAPS is defined. Signed-off-by:
Greg Kroah-Hartman <gregkh@suse.de> Signed-off-by:
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Harvey Harrison authored
security/smack/smack_lsm.c:1257:16: warning: Using plain integer as NULL pointer Signed-off-by:
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Andrew G. Morgan authored
Filesystem capability support makes it possible to do away with (set)uid-0 based privilege and use capabilities instead. That is, with filesystem support for capabilities but without this present patch, it is (conceptually) possible to manage a system with capabilities alone and never need to obtain privilege via (set)uid-0. Of course, conceptually isn't quite the same as currently possible since few user applications, certainly not enough to run a viable system, are currently prepared to leverage capabilities to exercise privilege. Further, many applications exist that may never get upgraded in this way, and the kernel will continue to want to support their setuid-0 base privilege needs. Where pure-capability applications evolve and replace setuid-0 binaries, it is desirable that there be a mechanisms by which they can contain their privilege. In addition to leveraging the per-process bounding and inheritable sets, this should include suppressing the privilege of the uid-0 superuser from the process' tree of children. The feature added by this patch can be leveraged to suppress the privilege associated with (set)uid-0. This suppression requires CAP_SETPCAP to initiate, and only immediately affects the 'current' process (it is inherited through fork()/exec()). This reimplementation differs significantly from the historical support for securebits which was system-wide, unwieldy and which has ultimately withered to a dead relic in the source of the modern kernel. With this patch applied a process, that is capable(CAP_SETPCAP), can now drop all legacy privilege (through uid=0) for itself and all subsequently fork()'d/exec()'d children with: prctl(PR_SET_SECUREBITS, 0x2f); This patch represents a no-op unless CONFIG_SECURITY_FILE_CAPABILITIES is enabled at configure time. [akpm@linux-foundation.org: fix uninitialised var warning] [serue@us.ibm.com: capabilities: use cap_task_prctl when !CONFIG_SECURITY] Signed-off-by:
Andrew G. Morgan <morgan@kernel.org> Acked-by:
James Morris <jmorris@namei.org> Cc: Stephen Smalley <sds@tycho.nsa.gov> Cc: Paul Moore <paul.moore@hp.com> Signed-off-by:
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Michael Hennerich authored
Don't perform kobjsize operations on objects the kernel doesn't manage. On Blackfin, drivers can get dma coherent memory by calling a function dma_alloc_coherent(). We do this in nommu by configuring a chunk of uncached memory at the top of memory. Since we don't want the kernel to use the uncached memory, we lie to the kernel, and tell it that it's max memory is between 0, and the start of the uncached dma coherent section. this all works well, until this memory gets exposed into userspace (with a frame buffer), when you look at the process's maps, it shows the framebuf: root:/proc> cat maps [snip] 03f0ef00-03f34700 rw-p 00000000 1f:00 192 /dev/fb0 root:/proc> This is outside the "normal" range for the kernel. When the kernel tries to find the size of this object (when you run ps), it dies in nommu.c in kobjsize. BUG_ON(page->index >= MAX_ORDER); since the page we are referring to is outside what the kernel thinks is it's max valid memory. root:~> while [ 1 ]; ps > /dev/null; done kernel BUG at mm/nommu.c:119! Kernel panic - not syncing: BUG! We fixed this by adding a check to reject out of range object pointers as it already does that for NULL pointers. Signed-off-by:
Michael Hennerich <Michael.Hennerich@analog.com> Signed-off-by:
Robin Getz <rgetz@blackfin.uclinux.org> Acked-by:
David Howells <dhowells@redhat.com> Signed-off-by:
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Dimitri Sivanich authored
We've found that it can take quite a bit of time (100's of usec) to get through the zone loop in refresh_cpu_vm_stats(). Adding a cond_resched() to allow other threads to run in the non-preemptive case. Signed-off-by:
Dimitri Sivanich <sivanich@sgi.com> Acked-by:
Christoph Lameter <clameter@sgi.com> Signed-off-by:
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KAMEZAWA Hiroyuki authored
This hack, "base = MAX_NR_ZONES", at __GFP_THISNODE was used for old zonliests. Now, new zonelist[] have a list for __GFP_THISNODE and this hack is incorrect. Should be removed. Signed-off-by:
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Mel Gorman <mel@csn.ul.ie> Cc: Christoph Lameter <clameter@sgi.com> Signed-off-by:
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Pavel Machek authored
Remove hand-coded get_order() from page_alloc.c. Signed-off-by:
Pavel Machek <pavel@suse.cz> Signed-off-by:
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Li Zefan authored
In commit 4c4a2214, we moved the memcontroller-related code from badness() to select_bad_process(), so the parameter 'mem' in badness() is unused now. Signed-off-by:
Li Zefan <lizf@cn.fujitsu.com> Acked-by:
Balbir Singh <balbir@linux.vnet.ibm.com> Signed-off-by:
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Yasunori Goto authored
This patch is to free memmaps which is allocated by bootmem. Freeing usemap is not necessary. The pages of usemap may be necessary for other sections. If removing section is last section on the node, its section is the final user of usemap page. (usemaps are allocated on its section by previous patch.) But it shouldn't be freed too, because the section must be logical offline state which all pages are isolated against page allocater. If it is freed, page alloctor may use it which will be removed physically soon. It will be disaster. So, this patch keeps it as it is. Signed-off-by:
Yasunori Goto <y-goto@jp.fujitsu.com> Cc: Badari Pulavarty <pbadari@us.ibm.com> Cc: Yinghai Lu <yhlu.kernel@gmail.com> Cc: Yasunori Goto <y-goto@jp.fujitsu.com> Signed-off-by:
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Yasunori Goto authored
Usemaps are allocated on the section which has pgdat by this. Because usemap size is very small, many other sections usemaps are allocated on only one page. If a section has usemap, it can't be removed until removing other sections. This dependency is not desirable for memory removing. Pgdat has similar feature. When a section has pgdat area, it must be the last section for removing on the node. So, if section A has pgdat and section B has usemap for section A, Both sections can't be removed due to dependency each other. To solve this issue, this patch collects usemap on same section with pgdat. If other sections doesn't have any dependency, this section will be able to be removed finally. Signed-off-by:
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Yasunori Goto authored
alloc_bootmem_section() can allocate specified section's area. This is used for usemap to keep same section with pgdat by later patch. Signed-off-by:
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Yasunori Goto authored
To free memmap easier, this patch aligns it to page size. Bootmem allocater may mix some objects in one pages. It's not good for freeing memmap of memory hot-remove. Signed-off-by:
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Yasunori Goto authored
This patch set is to free pages which is allocated by bootmem for memory-hotremove. Some structures of memory management are allocated by bootmem. ex) memmap, etc. To remove memory physically, some of them must be freed according to circumstance. This patch set makes basis to free those pages, and free memmaps. Basic my idea is using remain members of struct page to remember information of users of bootmem (section number or node id). When the section is removing, kernel can confirm it. By this information, some issues can be solved. 1) When the memmap of removing section is allocated on other section by bootmem, it should/can be free. 2) When the memmap of removing section is allocated on the same section, it shouldn't be freed. Because the section has to be logical memory offlined already and all pages must be isolated against page allocater. If it is freed, page allocator may use it which will be removed physically soon. 3) When removing section has other section's memmap, kernel will be able to show easily which section should be removed before it for user. (Not implemented yet) 4) When the above case 2), the page isolation will be able to check and skip memmap's page when logical memory offline (offline_pages()). Current page isolation code fails in this case because this page is just reserved page and it can't distinguish this pages can be removed or not. But, it will be able to do by this patch. (Not implemented yet.) 5) The node information like pgdat has similar issues. But, this will be able to be solved too by this. (Not implemented yet, but, remembering node id in the pages.) Fortunately, current bootmem allocator just keeps PageReserved flags, and doesn't use any other members of page struct. The users of bootmem doesn't use them too. This patch: This is to register information which is node or section's id. Kernel can distinguish which node/section uses the pages allcated by bootmem. This is basis for hot-remove sections or nodes. Signed-off-by: -
Gerald Schaefer authored
Huge ptes have a special type on s390 and cannot be handled with the standard pte functions in certain cases, e.g. because of a different location of the invalid bit. This patch adds some new architecture- specific functions to hugetlb common code, as a prerequisite for the s390 large page support. This won't affect other architectures in functionality, but I need to add some new dummy inline functions to the headers. Acked-by:
Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by:
Gerald Schaefer <gerald.schaefer@de.ibm.com> Cc: Paul Mundt <lethal@linux-sh.org> Cc: "Luck, Tony" <tony.luck@intel.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "David S. Miller" <davem@davemloft.net> Signed-off-by:
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Gerald Schaefer authored
A cow break on a hugetlbfs page with page_count > 1 will set a new pte with set_huge_pte_at(), w/o any tlb flush operation. The old pte will remain in the tlb and subsequent write access to the page will result in a page fault loop, for as long as it may take until the tlb is flushed from somewhere else. This patch introduces an architecture-specific huge_ptep_clear_flush() function, which is called before the the set_huge_pte_at() in hugetlb_cow(). ATTENTION: This is just a nop on all architectures for now, the s390 implementation will come with our large page patch later. Other architectures should define their own huge_ptep_clear_flush() if needed. Acked-by:
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Gerald Schaefer authored
This patch moves all architecture functions for hugetlb to architecture header files (include/asm-foo/hugetlb.h) and converts all macros to inline functions. It also removes (!) ARCH_HAS_HUGEPAGE_ONLY_RANGE, ARCH_HAS_HUGETLB_FREE_PGD_RANGE, ARCH_HAS_PREPARE_HUGEPAGE_RANGE, ARCH_HAS_SETCLEAR_HUGE_PTE and ARCH_HAS_HUGETLB_PREFAULT_HOOK. Getting rid of the ARCH_HAS_xxx #ifdef and macro fugliness should increase readability and maintainability, at the price of some code duplication. An asm-generic common part would have reduced the loc, but we would end up with new ARCH_HAS_xxx defines eventually. Acked-by:
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Lee Schermerhorn authored
This patch replaces the mempolicy mode, mode_flags, and nodemask in the shmem_sb_info struct with a struct mempolicy pointer, initialized to NULL. This removes dependency on the details of mempolicy from shmem.c and hugetlbfs inode.c and simplifies the interfaces. mpol_parse_str() in mempolicy.c is changed to return, via a pointer to a pointer arg, a struct mempolicy pointer on success. For MPOL_DEFAULT, the returned pointer is NULL. Further, mpol_parse_str() now takes a 'no_context' argument that causes the input nodemask to be stored in the w.user_nodemask of the created mempolicy for use when the mempolicy is installed in a tmpfs inode shared policy tree. At that time, any cpuset contextualization is applied to the original input nodemask. This preserves the previous behavior where the input nodemask was stored in the superblock. We can think of the returned mempolicy as "context free". Because mpol_parse_str() is now calling mpol_new(), we can remove from mpol_to_str() the semantic checks that mpol_new() already performs. Add 'no_context' parameter to mpol_to_str() to specify that it should format the nodemask in w.user_nodemask for 'bind' and 'interleave' policies. Change mpol_shared_policy_init() to take a pointer to a "context free" struct mempolicy and to create a new, "contextualized" mempolicy using the mode, mode_flags and user_nodemask from the input mempolicy. Note: we know that the mempolicy passed to mpol_to_str() or mpol_shared_policy_init() from a tmpfs superblock is "context free". This is currently the only instance thereof. However, if we found more uses for this concept, and introduced any ambiguity as to whether a mempolicy was context free or not, we could add another internal mode flag to identify context free mempolicies. Then, we could remove the 'no_context' argument from mpol_to_str(). Added shmem_get_sbmpol() to return a reference counted superblock mempolicy, if one exists, to pass to mpol_shared_policy_init(). We must add the reference under the sb stat_lock to prevent races with replacement of the mpol by remount. This reference is removed in mpol_shared_policy_init(). [akpm@linux-foundation.org: build fix] [akpm@linux-foundation.org: another build fix] [akpm@linux-foundation.org: yet another build fix] Signed-off-by:
Lee Schermerhorn <lee.schermerhorn@hp.com> Cc: Christoph Lameter <clameter@sgi.com> Cc: David Rientjes <rientjes@google.com> Cc: Mel Gorman <mel@csn.ul.ie> Cc: Andi Kleen <ak@suse.de> Signed-off-by:
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Lee Schermerhorn authored
For tmpfs/shmem shared policies, MPOL_DEFAULT is not necessarily equivalent to "local allocation". Because shared policies are at the same "scope" level [see Documentation/vm/numa_memory_policy.txt], as vma policies MPOL_DEFAULT means "fall back to current task policy". This patch extends the memory policy string parsing function to display "local" for MPOL_PREFERRED + MPOL_F_LOCAL. This allows one to specify local allocation as the default policy for shared memory areas via the tmpfs mpol mount option, regardless of the current task's policy. Also, "local" is now displayed for this policy. This patch allows us to accept the same input format as the display. Signed-off-by:
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Lee Schermerhorn authored
mm/shmem.c currently contains functions to parse and display memory policy strings for the tmpfs 'mpol' mount option. Move this to mm/mempolicy.c with the rest of the mempolicy support. With subsequent patches, we'll be able to remove knowledge of the details [mode, flags, policy, ...] completely from shmem.c 1) replace shmem_parse_mpol() in mm/shmem.c with mpol_parse_str() in mm/mempolicy.c. Rework to use the policy_types[] array [used by mpol_to_str()] to look up mode by name. 2) use mpol_to_str() to format policy for shmem_show_mpol(). mpol_to_str() expects a pointer to a struct mempolicy, so temporarily construct one. This will be replaced with a reference to a struct mempolicy in the tmpfs superblock in a subsequent patch. NOTE 1: I changed mpol_to_str() to use a colon ':' rather than an equal sign '=' as the nodemask delimiter to match mpol_parse_str() and the tmpfs/shmem mpol mount option formatting that now uses mpol_to_str(). This is a user visible change to numa_maps, but then the addition of the mode flags already changed the display. It makes sense to me to have the mounts and numa_maps display the policy in the same format. However, if anyone objects strongly, I can pass the desired nodemask delimeter as an arg to mpol_to_str(). Note 2: Like show_numa_map(), I don't check the return code from mpol_to_str(). I do use a longer buffer than the one provided by show_numa_map(), which seems to have sufficed so far. Signed-off-by:
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Lee Schermerhorn authored
mpol-to-str() formats memory policies into printable strings. Currently this is only used to display "numa_maps". A subsequent patch will use mpol_to_str() for formatting tmpfs [shmem] mpol mount options, allowing us to remove essentially duplicate code in mm/shmem.c. This patch cleans up mpol_to_str() generally and in preparation for that patch. 1) show_numa_maps() is not checking the return code from mpol_to_str(). There's not a lot we can do in this context if mpol_to_str() did return the error [insufficient space in buffer]. Proposed "solution": just check, under DEBUG_VM, that callers are providing sufficient buffer space for the policy, flags, and a few nodes. This way, we'll get some display. show_numa_maps() is providing a 50-byte buffer, so it won't trip this check. 50-bytes should be sufficient unless one has a large number of nodes in a very sparse nodemask. 2) The display of the new mode flags ["static" & "relative"] was set up to display multiple flags, separated by a "bar" '|'. However, this support is incomplete--e.g., need_bar was never incremented; and currently, these two flags are mutually exclusive. So remove the "bar" support, for now, and only display one flag. 3) Use snprint() to format flags, so as not to overflow the buffer. Not that it's ever happed, AFAIK. Signed-off-by:
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Lee Schermerhorn authored
Now that we're using "preferred local" policy for system default, we need to make this as fast as possible. Because of the variable size of the mempolicy structure [based on size of nodemasks], the preferred_node may be in a different cacheline from the mode. This can result in accessing an extra cacheline in the normal case of system default policy. Suspect this is the cause of an observed 2-3% slowdown in page fault testing relative to kernel without this patch series. To alleviate this, use an internal mode flag, MPOL_F_LOCAL in the mempolicy flags member which is guaranteed [?] to be in the same cacheline as the mode itself. Verified that reworked mempolicy now performs slightly better on 25-rc8-mm1 for both anon and shmem segments with system default and vma [preferred local] policy. Signed-off-by:
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Lee Schermerhorn authored
Here are a couple of "cleanups" for MPOL_PREFERRED behavior when v.preferred_node < 0 -- i.e., "local allocation": 1) [do_]get_mempolicy() calls the now renamed get_policy_nodemask() to fetch the nodemask associated with a policy. Currently, get_policy_nodemask() returns the set of nodes with memory, when the policy 'mode' is 'PREFERRED, and the preferred_node is < 0. Change to return an empty nodemask, as this is what was specified to achieve "local allocation". 2) When a task is moved into a [new] cpuset, mpol_rebind_policy() is called to adjust any task and vma policy nodes to be valid in the new cpuset. However, when the policy is MPOL_PREFERRED, and the preferred_node is <0, no rebind is necessary. The "local allocation" indication is valid in any cpuset. Existing code will "do the right thing" because node_remap() will just return the argument node when it is outside of the valid range of node ids. However, I think it is clearer and cleaner to skip the remap explicitly in this case. 3) mpol_to_str() produces a printable, "human readable" string from a struct mempolicy. For MPOL_PREFERRED with preferred_node <0, show "local", as this indicates local allocation, as the task migrates among nodes. Note that this matches the usage of "local allocation" in libnuma() and numactl. Without this change, I believe that node_set() [via set_bit()] will set bit 31, resulting in a misleading display. Signed-off-by: -
Lee Schermerhorn authored
Currently, when one specifies MPOL_DEFAULT via a NUMA memory policy API [set_mempolicy(), mbind() and internal versions], the kernel simply installs a NULL struct mempolicy pointer in the appropriate context: task policy, vma policy, or shared policy. This causes any use of that policy to "fall back" to the next most specific policy scope. The only use of MPOL_DEFAULT to mean "local allocation" is in the system default policy. This requires extra checks/cases for MPOL_DEFAULT in many mempolicy.c functions. There is another, "preferred" way to specify local allocation via the APIs. That is using the MPOL_PREFERRED policy mode with an empty nodemask. Internally, the empty nodemask gets converted to a preferred_node id of '-1'. All internal usage of MPOL_PREFERRED will convert the '-1' to the id of the node local to the cpu where the allocation occurs. System default policy, except during boot, is hard-coded to "local allocation". By using the MPOL_PREFERRED mode with a negative value of preferred node for system default policy, MPOL_DEFAULT will never occur in the 'policy' member of a struct mempolicy. Thus, we can remove all checks for MPOL_DEFAULT when converting policy to a node id/zonelist in the allocation paths. In slab_node() return local node id when policy pointer is NULL. No need to set a pol value to take the switch default. Replace switch default with BUG()--i.e., shouldn't happen. With this patch MPOL_DEFAULT is only used in the APIs, including internal calls to do_set_mempolicy() and in the display of policy in /proc/<pid>/numa_maps. It always means "fall back" to the the next most specific policy scope. This simplifies the description of memory policies quite a bit, with no visible change in behavior. get_mempolicy() continues to return MPOL_DEFAULT and an empty nodemask when the requested policy [task or vma/shared] is NULL. These are the values one would supply via set_mempolicy() or mbind() to achieve that condition--default behavior. This patch updates Documentation to reflect this change. Signed-off-by:
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Lee Schermerhorn authored
After further discussion with Christoph Lameter, it has become clear that my earlier attempts to clean up the mempolicy reference counting were a bit of overkill in some areas, resulting in superflous ref/unref in what are usually fast paths. In other areas, further inspection reveals that I botched the unref for interleave policies. A separate patch, suitable for upstream/stable trees, fixes up the known errors in the previous attempt to fix reference counting. This patch reworks the memory policy referencing counting and, one hopes, simplifies the code. Maybe I'll get it right this time. See the update to the numa_memory_policy.txt document for a discussion of memory policy reference counting that motivates this patch. Summary: Lookup of mempolicy, based on (vma, address) need only add a reference for shared policy, and we need only unref the policy when finished for shared policies. So, this patch backs out all of the unneeded extra reference counting added by my previous attempt. It then unrefs only shared policies when we're finished with them, using the mpol_cond_put() [conditional put] helper function introduced by this patch. Note that shmem_swapin() calls read_swap_cache_async() with a dummy vma containing just the policy. read_swap_cache_async() can call alloc_page_vma() multiple times, so we can't let alloc_page_vma() unref the shared policy in this case. To avoid this, we make a copy of any non-null shared policy and remove the MPOL_F_SHARED flag from the copy. This copy occurs before reading a page [or multiple pages] from swap, so the overhead should not be an issue here. I introduced a new static inline function "mpol_cond_copy()" to copy the shared policy to an on-stack policy and remove the flags that would require a conditional free. The current implementation of mpol_cond_copy() assumes that the struct mempolicy contains no pointers to dynamically allocated structures that must be duplicated or reference counted during copy. Signed-off-by:
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Lee Schermerhorn authored
Document mempolicy return value reference semantics assumed by the rest of the mempolicy code for the set_ and get_policy vm_ops in <linux/mm.h>--where the prototypes are defined--to inform any future mempolicy vm_op writers what the rest of the subsystem expects of them. Signed-off-by:
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Lee Schermerhorn authored
As part of yet another rework of mempolicy reference counting, we want to be able to identify shared policies efficiently, because they have an extra ref taken on lookup that needs to be removed when we're finished using the policy. Note: the extra ref is required because the policies are shared between tasks/processes and can be changed/freed by one task while another task is using them--e.g., for page allocation. Building on David Rientjes mempolicy "mode flags" enhancement, this patch indicates a "shared" policy by setting a new MPOL_F_SHARED flag in the flags member of the struct mempolicy added by David. MPOL_F_SHARED, and any future "internal mode flags" are reserved from bit zero up, as they will never be passed in the upper bits of the mode argument of a mempolicy API. I set the MPOL_F_SHARED flag when the policy is installed in the shared policy rb-tree. Don't need/want to clear the flag when removing from the tree as the mempolicy is freed [unref'd] internally to the sp_delete() function. However, a task could hold another reference on this mempolicy from a prior lookup. We need the MPOL_F_SHARED flag to stay put so that any tasks holding a ref will unref, eventually freeing, the mempolicy. A later patch in this series will introduce a function to conditionally unref [mpol_free] a policy. The MPOL_F_SHARED flag is one reason [currently the only reason] to unref/free a policy via the conditional free. Signed-off-by:
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