linux/fs/proc, branch v4.3

proc: convert to kstrto()/kstrto_from_user()

2015-09-10T20:29:01Z

Convert from manual allocation/copy_from_user/... to kstrto*() family which were designed for exactly that. One case can not be converted to kstrto*_from_user() to make code even more simpler because of whitespace stripping, oh well... Signed-off-by: Alexey Dobriyan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

proc: change proc_subdir_lock to a rwlock

2015-09-10T20:29:01Z

The proc_subdir_lock spinlock is used to allow only one task to make change to the proc directory structure as well as looking up information in it. However, the information lookup part can actually be entered by more than one task as the pde_get() and pde_put() reference count update calls in the critical sections are atomic increment and decrement respectively and so are safe with concurrent updates. The x86 architecture has already used qrwlock which is fair and other architectures like ARM are in the process of switching to qrwlock. So unfairness shouldn't be a concern in that conversion. This patch changed the proc_subdir_lock to a rwlock in order to enable concurrent lookup. The following functions were modified to take a write lock: - proc_register() - remove_proc_entry() - remove_proc_subtree() The following functions were modified to take a read lock: - xlate_proc_name() - proc_lookup_de() - proc_readdir_de() A parallel /proc filesystem search with the "find" command (1000 threads) was run on a 4-socket Haswell-EX box (144 threads). Before the patch, the parallel search took about 39s. After the patch, the parallel find took only 25s, a saving of about 14s. The micro-benchmark that I used was artificial, but it was used to reproduce an exit hanging problem that I saw in real application. In fact, only allow one task to do a lookup seems too limiting to me. Signed-off-by: Waiman Long Acked-by: "Eric W. Biederman" Cc: Alexey Dobriyan Cc: Nicolas Dichtel Cc: Al Viro Cc: Scott J Norton Cc: Douglas Hatch Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

procfs: always expose /proc//map_files/ and make it readable

2015-09-10T20:29:01Z

Currently, /proc//map_files/ is restricted to CAP_SYS_ADMIN, and is only exposed if CONFIG_CHECKPOINT_RESTORE is set. Each mapped file region gets a symlink in /proc//map_files/ corresponding to the virtual address range at which it is mapped. The symlinks work like the symlinks in /proc//fd/, so you can follow them to the backing file even if that backing file has been unlinked. Currently, files which are mapped, unlinked, and closed are impossible to stat() from userspace. Exposing /proc//map_files/ closes this functionality "hole". Not being able to stat() such files makes noticing and explicitly accounting for the space they use on the filesystem impossible. You can work around this by summing up the space used by every file in the filesystem and subtracting that total from what statfs() tells you, but that obviously isn't great, and it becomes unworkable once your filesystem becomes large enough. This patch moves map_files/ out from behind CONFIG_CHECKPOINT_RESTORE, and adjusts the permissions enforced on it as follows: * proc_map_files_lookup() * proc_map_files_readdir() * map_files_d_revalidate() Remove the CAP_SYS_ADMIN restriction, leaving only the current restriction requiring PTRACE_MODE_READ. The information made available to userspace by these three functions is already available in /proc/PID/maps with MODE_READ, so I don't see any reason to limit them any further (see below for more detail). * proc_map_files_follow_link() This stub has been added, and requires that the user have CAP_SYS_ADMIN in order to follow the links in map_files/, since there was concern on LKML both about the potential for bypassing permissions on ancestor directories in the path to files pointed to, and about what happens with more exotic memory mappings created by some drivers (ie dma-buf). In older versions of this patch, I changed every permission check in the four functions above to enforce MODE_ATTACH instead of MODE_READ. This was an oversight on my part, and after revisiting the discussion it seems that nobody was concerned about anything outside of what is made possible by ->follow_link(). So in this version, I've left the checks for PTRACE_MODE_READ as-is. [akpm@linux-foundation.org: catch up with concurrent proc_pid_follow_link() changes] Signed-off-by: Calvin Owens Reviewed-by: Kees Cook Cc: Andy Lutomirski Cc: Cyrill Gorcunov Cc: Joe Perches Cc: Kirill A. Shutemov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

proc: add cond_resched to /proc/kpage* read/write loop

2015-09-10T20:29:01Z

Reading/writing a /proc/kpage* file may take long on machines with a lot of RAM installed. Signed-off-by: Vladimir Davydov Suggested-by: Andres Lagar-Cavilla Reviewed-by: Andres Lagar-Cavilla Cc: Minchan Kim Cc: Raghavendra K T Cc: Johannes Weiner Cc: Michal Hocko Cc: Greg Thelen Cc: Michel Lespinasse Cc: David Rientjes Cc: Pavel Emelyanov Cc: Cyrill Gorcunov Cc: Jonathan Corbet Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

proc: export idle flag via kpageflags

2015-09-10T20:29:01Z

As noted by Minchan, a benefit of reading idle flag from /proc/kpageflags is that one can easily filter dirty and/or unevictable pages while estimating the size of unused memory. Note that idle flag read from /proc/kpageflags may be stale in case the page was accessed via a PTE, because it would be too costly to iterate over all page mappings on each /proc/kpageflags read to provide an up-to-date value. To make sure the flag is up-to-date one has to read /sys/kernel/mm/page_idle/bitmap first. Signed-off-by: Vladimir Davydov Reviewed-by: Andres Lagar-Cavilla Cc: Minchan Kim Cc: Raghavendra K T Cc: Johannes Weiner Cc: Michal Hocko Cc: Greg Thelen Cc: Michel Lespinasse Cc: David Rientjes Cc: Pavel Emelyanov Cc: Cyrill Gorcunov Cc: Jonathan Corbet Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: introduce idle page tracking

2015-09-10T20:29:01Z

Knowing the portion of memory that is not used by a certain application or memory cgroup (idle memory) can be useful for partitioning the system efficiently, e.g. by setting memory cgroup limits appropriately. Currently, the only means to estimate the amount of idle memory provided by the kernel is /proc/PID/{clear_refs,smaps}: the user can clear the access bit for all pages mapped to a particular process by writing 1 to clear_refs, wait for some time, and then count smaps:Referenced. However, this method has two serious shortcomings: - it does not count unmapped file pages - it affects the reclaimer logic To overcome these drawbacks, this patch introduces two new page flags, Idle and Young, and a new sysfs file, /sys/kernel/mm/page_idle/bitmap. A page's Idle flag can only be set from userspace by setting bit in /sys/kernel/mm/page_idle/bitmap at the offset corresponding to the page, and it is cleared whenever the page is accessed either through page tables (it is cleared in page_referenced() in this case) or using the read(2) system call (mark_page_accessed()). Thus by setting the Idle flag for pages of a particular workload, which can be found e.g. by reading /proc/PID/pagemap, waiting for some time to let the workload access its working set, and then reading the bitmap file, one can estimate the amount of pages that are not used by the workload. The Young page flag is used to avoid interference with the memory reclaimer. A page's Young flag is set whenever the Access bit of a page table entry pointing to the page is cleared by writing to the bitmap file. If page_referenced() is called on a Young page, it will add 1 to its return value, therefore concealing the fact that the Access bit was cleared. Note, since there is no room for extra page flags on 32 bit, this feature uses extended page flags when compiled on 32 bit. [akpm@linux-foundation.org: fix build] [akpm@linux-foundation.org: kpageidle requires an MMU] [akpm@linux-foundation.org: decouple from page-flags rework] Signed-off-by: Vladimir Davydov Reviewed-by: Andres Lagar-Cavilla Cc: Minchan Kim Cc: Raghavendra K T Cc: Johannes Weiner Cc: Michal Hocko Cc: Greg Thelen Cc: Michel Lespinasse Cc: David Rientjes Cc: Pavel Emelyanov Cc: Cyrill Gorcunov Cc: Jonathan Corbet Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

proc: add kpagecgroup file

2015-09-10T20:29:01Z

/proc/kpagecgroup contains a 64-bit inode number of the memory cgroup each page is charged to, indexed by PFN. Having this information is useful for estimating a cgroup working set size. The file is present if CONFIG_PROC_PAGE_MONITOR && CONFIG_MEMCG. Signed-off-by: Vladimir Davydov Reviewed-by: Andres Lagar-Cavilla Cc: Minchan Kim Cc: Raghavendra K T Cc: Johannes Weiner Cc: Michal Hocko Cc: Greg Thelen Cc: Michel Lespinasse Cc: David Rientjes Cc: Pavel Emelyanov Cc: Cyrill Gorcunov Cc: Jonathan Corbet Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: /proc/pid/smaps:: show proportional swap share of the mapping

2015-09-08T22:35:28Z

We want to know per-process workingset size for smart memory management on userland and we use swap(ex, zram) heavily to maximize memory efficiency so workingset includes swap as well as RSS. On such system, if there are lots of shared anonymous pages, it's really hard to figure out exactly how many each process consumes memory(ie, rss + wap) if the system has lots of shared anonymous memory(e.g, android). This patch introduces SwapPss field on /proc//smaps so we can get more exact workingset size per process. Bongkyu tested it. Result is below. 1. 50M used swap SwapTotal: 461976 kB SwapFree: 411192 kB $ adb shell cat /proc/*/smaps | grep "SwapPss:" | awk '{sum += $2} END {print sum}'; 48236 $ adb shell cat /proc/*/smaps | grep "Swap:" | awk '{sum += $2} END {print sum}'; 141184 2. 240M used swap SwapTotal: 461976 kB SwapFree: 216808 kB $ adb shell cat /proc/*/smaps | grep "SwapPss:" | awk '{sum += $2} END {print sum}'; 230315 $ adb shell cat /proc/*/smaps | grep "Swap:" | awk '{sum += $2} END {print sum}'; 1387744 [akpm@linux-foundation.org: simplify kunmap_atomic() call] Signed-off-by: Minchan Kim Reported-by: Bongkyu Kim Tested-by: Bongkyu Kim Cc: Hugh Dickins Cc: Sergey Senozhatsky Cc: Jonathan Corbet Cc: Jerome Marchand Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

pagemap: add mmap-exclusive bit for marking pages mapped only here

2015-09-08T22:35:28Z

This patch sets bit 56 in pagemap if this page is mapped only once. It allows to detect exclusively used pages without exposing PFN: present file exclusive state 0 0 0 non-present 1 1 0 file page mapped somewhere else 1 1 1 file page mapped only here 1 0 0 anon non-CoWed page (shared with parent/child) 1 0 1 anon CoWed page (or never forked) CoWed pages in (MAP_FILE | MAP_PRIVATE) areas are anon in this context. MMap-exclusive bit doesn't reflect potential page-sharing via swapcache: page could be mapped once but has several swap-ptes which point to it. Application could detect that by swap bit in pagemap entry and touch that pte via /proc/pid/mem to get real information. See http://lkml.kernel.org/r/CAEVpBa+_RyACkhODZrRvQLs80iy0sqpdrd0AaP_-tgnX3Y9yNQ@mail.gmail.com Requested by Mark Williamson. [akpm@linux-foundation.org: fix spello] Signed-off-by: Konstantin Khlebnikov Reviewed-by: Mark Williamson Tested-by: Mark Williamson Reviewed-by: Naoya Horiguchi Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

pagemap: hide physical addresses from non-privileged users

2015-09-08T22:35:28Z

This patch makes pagemap readable for normal users and hides physical addresses from them. For some use-cases PFN isn't required at all. See http://lkml.kernel.org/r/1425935472-17949-1-git-send-email-kirill@shutemov.name Fixes: ab676b7d6fbf ("pagemap: do not leak physical addresses to non-privileged userspace") Signed-off-by: Konstantin Khlebnikov Cc: Naoya Horiguchi Reviewed-by: Mark Williamson Tested-by: Mark Williamson Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

linux/fs/proc, branch v4.3

proc: convert to kstrto*()/kstrto*_from_user()

proc: change proc_subdir_lock to a rwlock

procfs: always expose /proc//map_files/ and make it readable

proc: add cond_resched to /proc/kpage* read/write loop

proc: export idle flag via kpageflags

mm: introduce idle page tracking

proc: add kpagecgroup file

mm: /proc/pid/smaps:: show proportional swap share of the mapping

pagemap: add mmap-exclusive bit for marking pages mapped only here

pagemap: hide physical addresses from non-privileged users

proc: convert to kstrto()/kstrto_from_user()