This patch add get_user_pages() variant that only succeeds if getting a reference to a page doesn't require major fault. Signed-off-by: Gleb Natapov <gleb@xxxxxxxxxx> --- fs/ncpfs/mmap.c | 2 ++ include/linux/mm.h | 5 +++++ mm/filemap.c | 3 +++ mm/memory.c | 31 ++++++++++++++++++++++++++++--- mm/shmem.c | 8 +++++++- 5 files changed, 45 insertions(+), 4 deletions(-) diff --git a/fs/ncpfs/mmap.c b/fs/ncpfs/mmap.c index 15458de..338527e 100644 --- a/fs/ncpfs/mmap.c +++ b/fs/ncpfs/mmap.c @@ -39,6 +39,8 @@ static int ncp_file_mmap_fault(struct vm_area_struct *area, int bufsize; int pos; /* XXX: loff_t ? */ + if (vmf->flags & FAULT_FLAG_MINOR) + return VM_FAULT_MAJOR | VM_FAULT_ERROR; /* * ncpfs has nothing against high pages as long * as recvmsg and memset works on it diff --git a/include/linux/mm.h b/include/linux/mm.h index 24c3956..2304181 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -136,6 +136,7 @@ extern pgprot_t protection_map[16]; #define FAULT_FLAG_WRITE 0x01 /* Fault was a write access */ #define FAULT_FLAG_NONLINEAR 0x02 /* Fault was via a nonlinear mapping */ #define FAULT_FLAG_MKWRITE 0x04 /* Fault was mkwrite of existing pte */ +#define FAULT_FLAG_MINOR 0x08 /* Do only minor fault */ /* * This interface is used by x86 PAT code to identify a pfn mapping that is @@ -821,6 +822,9 @@ extern int access_process_vm(struct task_struct *tsk, unsigned long addr, void * int get_user_pages(struct task_struct *tsk, struct mm_struct *mm, unsigned long start, int nr_pages, int write, int force, struct page **pages, struct vm_area_struct **vmas); +int get_user_pages_noio(struct task_struct *tsk, struct mm_struct *mm, + unsigned long start, int nr_pages, int write, int force, + struct page **pages, struct vm_area_struct **vmas); int get_user_pages_fast(unsigned long start, int nr_pages, int write, struct page **pages); struct page *get_dump_page(unsigned long addr); @@ -1239,6 +1243,7 @@ struct page *follow_page(struct vm_area_struct *, unsigned long address, #define FOLL_GET 0x04 /* do get_page on page */ #define FOLL_DUMP 0x08 /* give error on hole if it would be zero */ #define FOLL_FORCE 0x10 /* get_user_pages read/write w/o permission */ +#define FOLL_MINOR 0x20 /* do only minor page faults */ typedef int (*pte_fn_t)(pte_t *pte, pgtable_t token, unsigned long addr, void *data); diff --git a/mm/filemap.c b/mm/filemap.c index ef169f3..6ef29e0 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1530,6 +1530,9 @@ int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf) goto no_cached_page; } } else { + if (vmf->flags & FAULT_FLAG_MINOR) + return VM_FAULT_MAJOR | VM_FAULT_ERROR; + /* No page in the page cache at all */ do_sync_mmap_readahead(vma, ra, file, offset); count_vm_event(PGMAJFAULT); diff --git a/mm/memory.c b/mm/memory.c index 7e91b5f..b621526 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1318,10 +1318,13 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm, cond_resched(); while (!(page = follow_page(vma, start, foll_flags))) { int ret; + unsigned int fault_fl = + ((foll_flags & FOLL_WRITE) ? + FAULT_FLAG_WRITE : 0) | + ((foll_flags & FOLL_MINOR) ? + FAULT_FLAG_MINOR : 0); - ret = handle_mm_fault(mm, vma, start, - (foll_flags & FOLL_WRITE) ? - FAULT_FLAG_WRITE : 0); + ret = handle_mm_fault(mm, vma, start, fault_fl); if (ret & VM_FAULT_ERROR) { if (ret & VM_FAULT_OOM) @@ -1329,6 +1332,8 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm, if (ret & (VM_FAULT_HWPOISON|VM_FAULT_SIGBUS)) return i ? i : -EFAULT; + else if (ret & VM_FAULT_MAJOR) + return i ? i : -EFAULT; BUG(); } if (ret & VM_FAULT_MAJOR) @@ -1439,6 +1444,23 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm, } EXPORT_SYMBOL(get_user_pages); +int get_user_pages_noio(struct task_struct *tsk, struct mm_struct *mm, + unsigned long start, int nr_pages, int write, int force, + struct page **pages, struct vm_area_struct **vmas) +{ + int flags = FOLL_TOUCH | FOLL_MINOR; + + if (pages) + flags |= FOLL_GET; + if (write) + flags |= FOLL_WRITE; + if (force) + flags |= FOLL_FORCE; + + return __get_user_pages(tsk, mm, start, nr_pages, flags, pages, vmas); +} +EXPORT_SYMBOL(get_user_pages_noio); + /** * get_dump_page() - pin user page in memory while writing it to core dump * @addr: user address @@ -2518,6 +2540,9 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma, delayacct_set_flag(DELAYACCT_PF_SWAPIN); page = lookup_swap_cache(entry); if (!page) { + if (flags & FAULT_FLAG_MINOR) + return VM_FAULT_MAJOR | VM_FAULT_ERROR; + grab_swap_token(mm); /* Contend for token _before_ read-in */ page = swapin_readahead(entry, GFP_HIGHUSER_MOVABLE, vma, address); diff --git a/mm/shmem.c b/mm/shmem.c index 356dd99..6a9d3c0 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1218,6 +1218,7 @@ static int shmem_getpage(struct inode *inode, unsigned long idx, swp_entry_t swap; gfp_t gfp; int error; + int flags = type ? *type : 0; if (idx >= SHMEM_MAX_INDEX) return -EFBIG; @@ -1266,6 +1267,11 @@ repeat: swappage = lookup_swap_cache(swap); if (!swappage) { shmem_swp_unmap(entry); + if (flags & FAULT_FLAG_MINOR) { + spin_unlock(&info->lock); + *type = VM_FAULT_MAJOR | VM_FAULT_ERROR; + goto failed; + } /* here we actually do the io */ if (type && !(*type & VM_FAULT_MAJOR)) { __count_vm_event(PGMAJFAULT); @@ -1474,7 +1480,7 @@ static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf) { struct inode *inode = vma->vm_file->f_path.dentry->d_inode; int error; - int ret; + int ret = (int)vmf->flags; if (((loff_t)vmf->pgoff << PAGE_CACHE_SHIFT) >= i_size_read(inode)) return VM_FAULT_SIGBUS; -- 1.6.3.3 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html