From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 4641B1A1FD1 for ; Mon, 21 Mar 2016 06:22:56 -0700 (PDT) From: Jan Kara Subject: [PATCH 09/10] dax: Use radix tree entry lock to protect cow faults Date: Mon, 21 Mar 2016 14:22:54 +0100 Message-Id: <1458566575-28063-10-git-send-email-jack@suse.cz> In-Reply-To: <1458566575-28063-1-git-send-email-jack@suse.cz> References: <1458566575-28063-1-git-send-email-jack@suse.cz> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-nvdimm-bounces@lists.01.org Sender: "Linux-nvdimm" To: linux-fsdevel@vger.kernel.org Cc: Jan Kara , linux-nvdimm@lists.01.org, NeilBrown , "Wilcox, Matthew R" List-ID: When doing cow faults, we cannot directly fill in PTE as we do for other faults as we rely on generic code to do proper accounting of the cowed page. We also have no page to lock to protect against races with truncate as other faults have and we need the protection to extend until the moment generic code inserts cowed page into PTE thus at that point we have no protection of fs-specific i_mmap_sem. So far we relied on using i_mmap_lock for the protection however that is completely special to cow faults. To make fault locking more uniform use DAX entry lock instead. Signed-off-by: Jan Kara --- fs/dax.c | 12 +++++------- include/linux/dax.h | 1 + include/linux/mm.h | 7 +++++++ mm/memory.c | 38 ++++++++++++++++++-------------------- 4 files changed, 31 insertions(+), 27 deletions(-) diff --git a/fs/dax.c b/fs/dax.c index 4fcac59b6dcb..2fcf4e8a17c5 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -469,7 +469,7 @@ restart: return ret; } -static void unlock_mapping_entry(struct address_space *mapping, pgoff_t index) +void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index) { void *ret, **slot; wait_queue_head_t *wq = dax_entry_waitqueue(mapping, index); @@ -502,7 +502,7 @@ static void put_locked_mapping_entry(struct address_space *mapping, unlock_page(entry); page_cache_release(entry); } else { - unlock_mapping_entry(mapping, index); + dax_unlock_mapping_entry(mapping, index); } } @@ -887,12 +887,10 @@ int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf, goto unlock_entry; if (!radix_tree_exceptional_entry(entry)) { vmf->page = entry; - } else { - unlock_mapping_entry(mapping, vmf->pgoff); - i_mmap_lock_read(mapping); - vmf->page = NULL; + return VM_FAULT_LOCKED; } - return VM_FAULT_LOCKED; + vmf->entry = entry; + return VM_FAULT_DAX_LOCKED; } if (!buffer_mapped(&bh)) { diff --git a/include/linux/dax.h b/include/linux/dax.h index da2416d916e6..29a83a767ea3 100644 --- a/include/linux/dax.h +++ b/include/linux/dax.h @@ -60,4 +60,5 @@ static inline bool dax_mapping(struct address_space *mapping) struct writeback_control; int dax_writeback_mapping_range(struct address_space *mapping, struct block_device *bdev, struct writeback_control *wbc); +void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index); #endif diff --git a/include/linux/mm.h b/include/linux/mm.h index 450fc977ed02..1c64039dc505 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -299,6 +299,12 @@ struct vm_fault { * is set (which is also implied by * VM_FAULT_ERROR). */ + void *entry; /* ->fault handler can alternatively + * return locked DAX entry. In that + * case handler should return + * VM_FAULT_DAX_LOCKED and fill in + * entry here. + */ /* for ->map_pages() only */ pgoff_t max_pgoff; /* map pages for offset from pgoff till * max_pgoff inclusive */ @@ -1084,6 +1090,7 @@ static inline void clear_page_pfmemalloc(struct page *page) #define VM_FAULT_LOCKED 0x0200 /* ->fault locked the returned page */ #define VM_FAULT_RETRY 0x0400 /* ->fault blocked, must retry */ #define VM_FAULT_FALLBACK 0x0800 /* huge page fault failed, fall back to small */ +#define VM_FAULT_DAX_LOCKED 0x1000 /* ->fault has locked DAX entry */ #define VM_FAULT_HWPOISON_LARGE_MASK 0xf000 /* encodes hpage index for large hwpoison */ diff --git a/mm/memory.c b/mm/memory.c index 81dca0083fcd..7a704d3cd3b5 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -63,6 +63,7 @@ #include #include #include +#include #include #include @@ -2783,7 +2784,8 @@ oom: */ static int __do_fault(struct vm_area_struct *vma, unsigned long address, pgoff_t pgoff, unsigned int flags, - struct page *cow_page, struct page **page) + struct page *cow_page, struct page **page, + void **entry) { struct vm_fault vmf; int ret; @@ -2798,8 +2800,10 @@ static int __do_fault(struct vm_area_struct *vma, unsigned long address, ret = vma->vm_ops->fault(vma, &vmf); if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY))) return ret; - if (!vmf.page) - goto out; + if (ret & VM_FAULT_DAX_LOCKED) { + *entry = vmf.entry; + return ret; + } if (unlikely(PageHWPoison(vmf.page))) { if (ret & VM_FAULT_LOCKED) @@ -2813,7 +2817,6 @@ static int __do_fault(struct vm_area_struct *vma, unsigned long address, else VM_BUG_ON_PAGE(!PageLocked(vmf.page), vmf.page); - out: *page = vmf.page; return ret; } @@ -2985,7 +2988,7 @@ static int do_read_fault(struct mm_struct *mm, struct vm_area_struct *vma, pte_unmap_unlock(pte, ptl); } - ret = __do_fault(vma, address, pgoff, flags, NULL, &fault_page); + ret = __do_fault(vma, address, pgoff, flags, NULL, &fault_page, NULL); if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY))) return ret; @@ -3008,6 +3011,7 @@ static int do_cow_fault(struct mm_struct *mm, struct vm_area_struct *vma, pgoff_t pgoff, unsigned int flags, pte_t orig_pte) { struct page *fault_page, *new_page; + void *fault_entry; struct mem_cgroup *memcg; spinlock_t *ptl; pte_t *pte; @@ -3025,26 +3029,24 @@ static int do_cow_fault(struct mm_struct *mm, struct vm_area_struct *vma, return VM_FAULT_OOM; } - ret = __do_fault(vma, address, pgoff, flags, new_page, &fault_page); + ret = __do_fault(vma, address, pgoff, flags, new_page, &fault_page, + &fault_entry); if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY))) goto uncharge_out; - if (fault_page) + if (!(ret & VM_FAULT_DAX_LOCKED)) copy_user_highpage(new_page, fault_page, address, vma); __SetPageUptodate(new_page); pte = pte_offset_map_lock(mm, pmd, address, &ptl); if (unlikely(!pte_same(*pte, orig_pte))) { pte_unmap_unlock(pte, ptl); - if (fault_page) { + if (!(ret & VM_FAULT_DAX_LOCKED)) { unlock_page(fault_page); page_cache_release(fault_page); } else { - /* - * The fault handler has no page to lock, so it holds - * i_mmap_lock for read to protect against truncate. - */ - i_mmap_unlock_read(vma->vm_file->f_mapping); + dax_unlock_mapping_entry(vma->vm_file->f_mapping, + pgoff); } goto uncharge_out; } @@ -3052,15 +3054,11 @@ static int do_cow_fault(struct mm_struct *mm, struct vm_area_struct *vma, mem_cgroup_commit_charge(new_page, memcg, false, false); lru_cache_add_active_or_unevictable(new_page, vma); pte_unmap_unlock(pte, ptl); - if (fault_page) { + if (!(ret & VM_FAULT_DAX_LOCKED)) { unlock_page(fault_page); page_cache_release(fault_page); } else { - /* - * The fault handler has no page to lock, so it holds - * i_mmap_lock for read to protect against truncate. - */ - i_mmap_unlock_read(vma->vm_file->f_mapping); + dax_unlock_mapping_entry(vma->vm_file->f_mapping, pgoff); } return ret; uncharge_out: @@ -3080,7 +3078,7 @@ static int do_shared_fault(struct mm_struct *mm, struct vm_area_struct *vma, int dirtied = 0; int ret, tmp; - ret = __do_fault(vma, address, pgoff, flags, NULL, &fault_page); + ret = __do_fault(vma, address, pgoff, flags, NULL, &fault_page, NULL); if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY))) return ret; -- 2.6.2 _______________________________________________ Linux-nvdimm mailing list Linux-nvdimm@lists.01.org https://lists.01.org/mailman/listinfo/linux-nvdimm From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de ([195.135.220.15]:51717 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755257AbcCUNWd (ORCPT ); Mon, 21 Mar 2016 09:22:33 -0400 From: Jan Kara To: linux-fsdevel@vger.kernel.org Cc: "Wilcox, Matthew R" , Ross Zwisler , Dan Williams , linux-nvdimm@lists.01.org, NeilBrown , Jan Kara Subject: [PATCH 09/10] dax: Use radix tree entry lock to protect cow faults Date: Mon, 21 Mar 2016 14:22:54 +0100 Message-Id: <1458566575-28063-10-git-send-email-jack@suse.cz> In-Reply-To: <1458566575-28063-1-git-send-email-jack@suse.cz> References: <1458566575-28063-1-git-send-email-jack@suse.cz> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: When doing cow faults, we cannot directly fill in PTE as we do for other faults as we rely on generic code to do proper accounting of the cowed page. We also have no page to lock to protect against races with truncate as other faults have and we need the protection to extend until the moment generic code inserts cowed page into PTE thus at that point we have no protection of fs-specific i_mmap_sem. So far we relied on using i_mmap_lock for the protection however that is completely special to cow faults. To make fault locking more uniform use DAX entry lock instead. Signed-off-by: Jan Kara --- fs/dax.c | 12 +++++------- include/linux/dax.h | 1 + include/linux/mm.h | 7 +++++++ mm/memory.c | 38 ++++++++++++++++++-------------------- 4 files changed, 31 insertions(+), 27 deletions(-) diff --git a/fs/dax.c b/fs/dax.c index 4fcac59b6dcb..2fcf4e8a17c5 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -469,7 +469,7 @@ restart: return ret; } -static void unlock_mapping_entry(struct address_space *mapping, pgoff_t index) +void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index) { void *ret, **slot; wait_queue_head_t *wq = dax_entry_waitqueue(mapping, index); @@ -502,7 +502,7 @@ static void put_locked_mapping_entry(struct address_space *mapping, unlock_page(entry); page_cache_release(entry); } else { - unlock_mapping_entry(mapping, index); + dax_unlock_mapping_entry(mapping, index); } } @@ -887,12 +887,10 @@ int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf, goto unlock_entry; if (!radix_tree_exceptional_entry(entry)) { vmf->page = entry; - } else { - unlock_mapping_entry(mapping, vmf->pgoff); - i_mmap_lock_read(mapping); - vmf->page = NULL; + return VM_FAULT_LOCKED; } - return VM_FAULT_LOCKED; + vmf->entry = entry; + return VM_FAULT_DAX_LOCKED; } if (!buffer_mapped(&bh)) { diff --git a/include/linux/dax.h b/include/linux/dax.h index da2416d916e6..29a83a767ea3 100644 --- a/include/linux/dax.h +++ b/include/linux/dax.h @@ -60,4 +60,5 @@ static inline bool dax_mapping(struct address_space *mapping) struct writeback_control; int dax_writeback_mapping_range(struct address_space *mapping, struct block_device *bdev, struct writeback_control *wbc); +void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index); #endif diff --git a/include/linux/mm.h b/include/linux/mm.h index 450fc977ed02..1c64039dc505 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -299,6 +299,12 @@ struct vm_fault { * is set (which is also implied by * VM_FAULT_ERROR). */ + void *entry; /* ->fault handler can alternatively + * return locked DAX entry. In that + * case handler should return + * VM_FAULT_DAX_LOCKED and fill in + * entry here. + */ /* for ->map_pages() only */ pgoff_t max_pgoff; /* map pages for offset from pgoff till * max_pgoff inclusive */ @@ -1084,6 +1090,7 @@ static inline void clear_page_pfmemalloc(struct page *page) #define VM_FAULT_LOCKED 0x0200 /* ->fault locked the returned page */ #define VM_FAULT_RETRY 0x0400 /* ->fault blocked, must retry */ #define VM_FAULT_FALLBACK 0x0800 /* huge page fault failed, fall back to small */ +#define VM_FAULT_DAX_LOCKED 0x1000 /* ->fault has locked DAX entry */ #define VM_FAULT_HWPOISON_LARGE_MASK 0xf000 /* encodes hpage index for large hwpoison */ diff --git a/mm/memory.c b/mm/memory.c index 81dca0083fcd..7a704d3cd3b5 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -63,6 +63,7 @@ #include #include #include +#include #include #include @@ -2783,7 +2784,8 @@ oom: */ static int __do_fault(struct vm_area_struct *vma, unsigned long address, pgoff_t pgoff, unsigned int flags, - struct page *cow_page, struct page **page) + struct page *cow_page, struct page **page, + void **entry) { struct vm_fault vmf; int ret; @@ -2798,8 +2800,10 @@ static int __do_fault(struct vm_area_struct *vma, unsigned long address, ret = vma->vm_ops->fault(vma, &vmf); if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY))) return ret; - if (!vmf.page) - goto out; + if (ret & VM_FAULT_DAX_LOCKED) { + *entry = vmf.entry; + return ret; + } if (unlikely(PageHWPoison(vmf.page))) { if (ret & VM_FAULT_LOCKED) @@ -2813,7 +2817,6 @@ static int __do_fault(struct vm_area_struct *vma, unsigned long address, else VM_BUG_ON_PAGE(!PageLocked(vmf.page), vmf.page); - out: *page = vmf.page; return ret; } @@ -2985,7 +2988,7 @@ static int do_read_fault(struct mm_struct *mm, struct vm_area_struct *vma, pte_unmap_unlock(pte, ptl); } - ret = __do_fault(vma, address, pgoff, flags, NULL, &fault_page); + ret = __do_fault(vma, address, pgoff, flags, NULL, &fault_page, NULL); if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY))) return ret; @@ -3008,6 +3011,7 @@ static int do_cow_fault(struct mm_struct *mm, struct vm_area_struct *vma, pgoff_t pgoff, unsigned int flags, pte_t orig_pte) { struct page *fault_page, *new_page; + void *fault_entry; struct mem_cgroup *memcg; spinlock_t *ptl; pte_t *pte; @@ -3025,26 +3029,24 @@ static int do_cow_fault(struct mm_struct *mm, struct vm_area_struct *vma, return VM_FAULT_OOM; } - ret = __do_fault(vma, address, pgoff, flags, new_page, &fault_page); + ret = __do_fault(vma, address, pgoff, flags, new_page, &fault_page, + &fault_entry); if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY))) goto uncharge_out; - if (fault_page) + if (!(ret & VM_FAULT_DAX_LOCKED)) copy_user_highpage(new_page, fault_page, address, vma); __SetPageUptodate(new_page); pte = pte_offset_map_lock(mm, pmd, address, &ptl); if (unlikely(!pte_same(*pte, orig_pte))) { pte_unmap_unlock(pte, ptl); - if (fault_page) { + if (!(ret & VM_FAULT_DAX_LOCKED)) { unlock_page(fault_page); page_cache_release(fault_page); } else { - /* - * The fault handler has no page to lock, so it holds - * i_mmap_lock for read to protect against truncate. - */ - i_mmap_unlock_read(vma->vm_file->f_mapping); + dax_unlock_mapping_entry(vma->vm_file->f_mapping, + pgoff); } goto uncharge_out; } @@ -3052,15 +3054,11 @@ static int do_cow_fault(struct mm_struct *mm, struct vm_area_struct *vma, mem_cgroup_commit_charge(new_page, memcg, false, false); lru_cache_add_active_or_unevictable(new_page, vma); pte_unmap_unlock(pte, ptl); - if (fault_page) { + if (!(ret & VM_FAULT_DAX_LOCKED)) { unlock_page(fault_page); page_cache_release(fault_page); } else { - /* - * The fault handler has no page to lock, so it holds - * i_mmap_lock for read to protect against truncate. - */ - i_mmap_unlock_read(vma->vm_file->f_mapping); + dax_unlock_mapping_entry(vma->vm_file->f_mapping, pgoff); } return ret; uncharge_out: @@ -3080,7 +3078,7 @@ static int do_shared_fault(struct mm_struct *mm, struct vm_area_struct *vma, int dirtied = 0; int ret, tmp; - ret = __do_fault(vma, address, pgoff, flags, NULL, &fault_page); + ret = __do_fault(vma, address, pgoff, flags, NULL, &fault_page, NULL); if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY))) return ret; -- 2.6.2