From: Michal Hocko <mhocko@xxxxxxxx> Subject: mm: make mmap_sem for write waits killable for mm syscalls This is a follow up work for oom_reaper [1]. As the async OOM killing depends on oom_sem for read we would really appreciate if a holder for write didn't stood in the way. This patchset is changing many of down_write calls to be killable to help those cases when the writer is blocked and waiting for readers to release the lock and so help __oom_reap_task to process the oom victim. Most of the patches are really trivial because the lock is help from a shallow syscall paths where we can return EINTR trivially and allow the current task to die (note that EINTR will never get to the userspace as the task has fatal signal pending). Others seem to be easy as well as the callers are already handling fatal errors and bail and return to userspace which should be sufficient to handle the failure gracefully. I am not familiar with all those code paths so a deeper review is really appreciated. As this work is touching more areas which are not directly connected I have tried to keep the CC list as small as possible and people who I believed would be familiar are CCed only to the specific patches (all should have received the cover though). This patchset is based on linux-next and it depends on down_write_killable for rw_semaphores which got merged into tip locking/rwsem branch and it is merged into this next tree. I guess it would be easiest to route these patches via mmotm because of the dependency on the tip tree but if respective maintainers prefer other way I have no objections. I haven't covered all the mmap_write(mm->mmap_sem) instances here $ git grep "down_write(.*\<mmap_sem\>)" next/master | wc -l 98 $ git grep "down_write(.*\<mmap_sem\>)" | wc -l 62 I have tried to cover those which should be relatively easy to review in this series because this alone should be a nice improvement. Other places can be changed on top. [0] http://lkml.kernel.org/r/1456752417-9626-1-git-send-email-mhocko@xxxxxxxxxx [1] http://lkml.kernel.org/r/1452094975-551-1-git-send-email-mhocko@xxxxxxxxxx [2] http://lkml.kernel.org/r/1456750705-7141-1-git-send-email-mhocko@xxxxxxxxxx This patch (of 18): This is the first step in making mmap_sem write waiters killable. It focuses on the trivial ones which are taking the lock early after entering the syscall and they are not changing state before. Therefore it is very easy to change them to use down_write_killable and immediately return with -EINTR. This will allow the waiter to pass away without blocking the mmap_sem which might be required to make a forward progress. E.g. the oom reaper will need the lock for reading to dismantle the OOM victim address space. The only tricky function in this patch is vm_mmap_pgoff which has many call sites via vm_mmap. To reduce the risk keep vm_mmap with the original non-killable semantic for now. vm_munmap callers do not bother checking the return value so open code it into the munmap syscall path for now for simplicity. Signed-off-by: Michal Hocko <mhocko@xxxxxxxx> Acked-by: Vlastimil Babka <vbabka@xxxxxxx> Cc: Mel Gorman <mgorman@xxxxxxx> Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Konstantin Khlebnikov <koct9i@xxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/internal.h | 5 +++-- mm/madvise.c | 8 +++++--- mm/mlock.c | 16 ++++++++++------ mm/mmap.c | 27 +++++++++++++++++++++++---- mm/mprotect.c | 3 ++- mm/mremap.c | 3 ++- mm/nommu.c | 2 +- mm/util.c | 12 +++++++++--- 8 files changed, 55 insertions(+), 21 deletions(-) diff -puN mm/internal.h~mm-make-mmap_sem-for-write-waits-killable-for-mm-syscalls mm/internal.h --- a/mm/internal.h~mm-make-mmap_sem-for-write-waits-killable-for-mm-syscalls +++ a/mm/internal.h @@ -442,9 +442,10 @@ extern u64 hwpoison_filter_flags_value; extern u64 hwpoison_filter_memcg; extern u32 hwpoison_filter_enable; -extern unsigned long vm_mmap_pgoff(struct file *, unsigned long, +extern unsigned long __must_check vm_mmap_pgoff(struct file *, unsigned long, unsigned long, unsigned long, - unsigned long, unsigned long); + unsigned long, unsigned long, + bool); extern void set_pageblock_order(void); unsigned long reclaim_clean_pages_from_list(struct zone *zone, diff -puN mm/madvise.c~mm-make-mmap_sem-for-write-waits-killable-for-mm-syscalls mm/madvise.c --- a/mm/madvise.c~mm-make-mmap_sem-for-write-waits-killable-for-mm-syscalls +++ a/mm/madvise.c @@ -707,10 +707,12 @@ SYSCALL_DEFINE3(madvise, unsigned long, return error; write = madvise_need_mmap_write(behavior); - if (write) - down_write(¤t->mm->mmap_sem); - else + if (write) { + if (down_write_killable(¤t->mm->mmap_sem)) + return -EINTR; + } else { down_read(¤t->mm->mmap_sem); + } /* * If the interval [start,end) covers some unmapped address diff -puN mm/mlock.c~mm-make-mmap_sem-for-write-waits-killable-for-mm-syscalls mm/mlock.c --- a/mm/mlock.c~mm-make-mmap_sem-for-write-waits-killable-for-mm-syscalls +++ a/mm/mlock.c @@ -617,7 +617,7 @@ static int apply_vma_lock_flags(unsigned return error; } -static int do_mlock(unsigned long start, size_t len, vm_flags_t flags) +static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t flags) { unsigned long locked; unsigned long lock_limit; @@ -635,7 +635,8 @@ static int do_mlock(unsigned long start, lock_limit >>= PAGE_SHIFT; locked = len >> PAGE_SHIFT; - down_write(¤t->mm->mmap_sem); + if (down_write_killable(¤t->mm->mmap_sem)) + return -EINTR; locked += current->mm->locked_vm; @@ -678,7 +679,8 @@ SYSCALL_DEFINE2(munlock, unsigned long, len = PAGE_ALIGN(len + (offset_in_page(start))); start &= PAGE_MASK; - down_write(¤t->mm->mmap_sem); + if (down_write_killable(¤t->mm->mmap_sem)) + return -EINTR; ret = apply_vma_lock_flags(start, len, 0); up_write(¤t->mm->mmap_sem); @@ -748,9 +750,10 @@ SYSCALL_DEFINE1(mlockall, int, flags) lock_limit = rlimit(RLIMIT_MEMLOCK); lock_limit >>= PAGE_SHIFT; - ret = -ENOMEM; - down_write(¤t->mm->mmap_sem); + if (down_write_killable(¤t->mm->mmap_sem)) + return -EINTR; + ret = -ENOMEM; if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) || capable(CAP_IPC_LOCK)) ret = apply_mlockall_flags(flags); @@ -765,7 +768,8 @@ SYSCALL_DEFINE0(munlockall) { int ret; - down_write(¤t->mm->mmap_sem); + if (down_write_killable(¤t->mm->mmap_sem)) + return -EINTR; ret = apply_mlockall_flags(0); up_write(¤t->mm->mmap_sem); return ret; diff -puN mm/mmap.c~mm-make-mmap_sem-for-write-waits-killable-for-mm-syscalls mm/mmap.c --- a/mm/mmap.c~mm-make-mmap_sem-for-write-waits-killable-for-mm-syscalls +++ a/mm/mmap.c @@ -178,7 +178,8 @@ SYSCALL_DEFINE1(brk, unsigned long, brk) unsigned long min_brk; bool populate; - down_write(&mm->mmap_sem); + if (down_write_killable(&mm->mmap_sem)) + return -EINTR; #ifdef CONFIG_COMPAT_BRK /* @@ -1332,7 +1333,7 @@ SYSCALL_DEFINE6(mmap_pgoff, unsigned lon flags &= ~(MAP_EXECUTABLE | MAP_DENYWRITE); - retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff); + retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff, true); out_fput: if (file) fput(file); @@ -2493,6 +2494,10 @@ int vm_munmap(unsigned long start, size_ int ret; struct mm_struct *mm = current->mm; + /* + * XXX convert to down_write_killable as soon as all users are able + * to handle the error. + */ down_write(&mm->mmap_sem); ret = do_munmap(mm, start, len); up_write(&mm->mmap_sem); @@ -2502,8 +2507,15 @@ EXPORT_SYMBOL(vm_munmap); SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len) { + int ret; + struct mm_struct *mm = current->mm; + profile_munmap(addr); - return vm_munmap(addr, len); + if (down_write_killable(&mm->mmap_sem)) + return -EINTR; + ret = do_munmap(mm, addr, len); + up_write(&mm->mmap_sem); + return ret; } @@ -2535,7 +2547,9 @@ SYSCALL_DEFINE5(remap_file_pages, unsign if (pgoff + (size >> PAGE_SHIFT) < pgoff) return ret; - down_write(&mm->mmap_sem); + if (down_write_killable(&mm->mmap_sem)) + return -EINTR; + vma = find_vma(mm, start); if (!vma || !(vma->vm_flags & VM_SHARED)) @@ -2700,6 +2714,11 @@ unsigned long vm_brk(unsigned long addr, unsigned long ret; bool populate; + /* + * XXX not all users are chcecking the return value, convert + * to down_write_killable after they are able to cope with + * error + */ down_write(&mm->mmap_sem); ret = do_brk(addr, len); populate = ((mm->def_flags & VM_LOCKED) != 0); diff -puN mm/mprotect.c~mm-make-mmap_sem-for-write-waits-killable-for-mm-syscalls mm/mprotect.c --- a/mm/mprotect.c~mm-make-mmap_sem-for-write-waits-killable-for-mm-syscalls +++ a/mm/mprotect.c @@ -379,7 +379,8 @@ SYSCALL_DEFINE3(mprotect, unsigned long, reqprot = prot; - down_write(¤t->mm->mmap_sem); + if (down_write_killable(¤t->mm->mmap_sem)) + return -EINTR; vma = find_vma(current->mm, start); error = -ENOMEM; diff -puN mm/mremap.c~mm-make-mmap_sem-for-write-waits-killable-for-mm-syscalls mm/mremap.c --- a/mm/mremap.c~mm-make-mmap_sem-for-write-waits-killable-for-mm-syscalls +++ a/mm/mremap.c @@ -503,7 +503,8 @@ SYSCALL_DEFINE5(mremap, unsigned long, a if (!new_len) return ret; - down_write(¤t->mm->mmap_sem); + if (down_write_killable(¤t->mm->mmap_sem)) + return -EINTR; if (flags & MREMAP_FIXED) { ret = mremap_to(addr, old_len, new_addr, new_len, diff -puN mm/nommu.c~mm-make-mmap_sem-for-write-waits-killable-for-mm-syscalls mm/nommu.c --- a/mm/nommu.c~mm-make-mmap_sem-for-write-waits-killable-for-mm-syscalls +++ a/mm/nommu.c @@ -1446,7 +1446,7 @@ SYSCALL_DEFINE6(mmap_pgoff, unsigned lon flags &= ~(MAP_EXECUTABLE | MAP_DENYWRITE); - retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff); + retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff, true); if (file) fput(file); diff -puN mm/util.c~mm-make-mmap_sem-for-write-waits-killable-for-mm-syscalls mm/util.c --- a/mm/util.c~mm-make-mmap_sem-for-write-waits-killable-for-mm-syscalls +++ a/mm/util.c @@ -289,7 +289,7 @@ EXPORT_SYMBOL_GPL(get_user_pages_fast); unsigned long vm_mmap_pgoff(struct file *file, unsigned long addr, unsigned long len, unsigned long prot, - unsigned long flag, unsigned long pgoff) + unsigned long flag, unsigned long pgoff, bool killable) { unsigned long ret; struct mm_struct *mm = current->mm; @@ -297,7 +297,12 @@ unsigned long vm_mmap_pgoff(struct file ret = security_mmap_file(file, prot, flag); if (!ret) { - down_write(&mm->mmap_sem); + if (killable) { + if (down_write_killable(&mm->mmap_sem)) + return -EINTR; + } else { + down_write(&mm->mmap_sem); + } ret = do_mmap_pgoff(file, addr, len, prot, flag, pgoff, &populate); up_write(&mm->mmap_sem); @@ -307,6 +312,7 @@ unsigned long vm_mmap_pgoff(struct file return ret; } +/* XXX are all callers checking an error */ unsigned long vm_mmap(struct file *file, unsigned long addr, unsigned long len, unsigned long prot, unsigned long flag, unsigned long offset) @@ -316,7 +322,7 @@ unsigned long vm_mmap(struct file *file, if (unlikely(offset_in_page(offset))) return -EINVAL; - return vm_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT); + return vm_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT, false); } EXPORT_SYMBOL(vm_mmap); _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
