diff options
| -rw-r--r-- | Documentation/filesystems/locking.rst | 62 | ||||
| -rw-r--r-- | fs/inode.c | 2 | ||||
| -rw-r--r-- | include/linux/fs.h | 33 | ||||
| -rw-r--r-- | mm/filemap.c | 97 | ||||
| -rw-r--r-- | mm/readahead.c | 2 | ||||
| -rw-r--r-- | mm/rmap.c | 37 | ||||
| -rw-r--r-- | mm/truncate.c | 3 |
7 files changed, 180 insertions, 56 deletions
diff --git a/Documentation/filesystems/locking.rst b/Documentation/filesystems/locking.rst index cdf15492c699..38a3097b6f1c 100644 --- a/Documentation/filesystems/locking.rst +++ b/Documentation/filesystems/locking.rst @@ -271,19 +271,19 @@ prototypes:: locking rules: All except set_page_dirty and freepage may block -====================== ======================== ========= -ops PageLocked(page) i_rwsem -====================== ======================== ========= +====================== ======================== ========= =============== +ops PageLocked(page) i_rwsem invalidate_lock +====================== ======================== ========= =============== writepage: yes, unlocks (see below) -readpage: yes, unlocks +readpage: yes, unlocks shared writepages: set_page_dirty no -readahead: yes, unlocks -readpages: no +readahead: yes, unlocks shared +readpages: no shared write_begin: locks the page exclusive write_end: yes, unlocks exclusive bmap: -invalidatepage: yes +invalidatepage: yes exclusive releasepage: yes freepage: yes direct_IO: @@ -378,7 +378,10 @@ keep it that way and don't breed new callers. ->invalidatepage() is called when the filesystem must attempt to drop some or all of the buffers from the page when it is being truncated. It returns zero on success. If ->invalidatepage is zero, the kernel uses -block_invalidatepage() instead. +block_invalidatepage() instead. The filesystem must exclusively acquire +invalidate_lock before invalidating page cache in truncate / hole punch path +(and thus calling into ->invalidatepage) to block races between page cache +invalidation and page cache filling functions (fault, read, ...). ->releasepage() is called when the kernel is about to try to drop the buffers from the page in preparation for freeing it. It returns zero to @@ -573,6 +576,25 @@ in sys_read() and friends. the lease within the individual filesystem to record the result of the operation +->fallocate implementation must be really careful to maintain page cache +consistency when punching holes or performing other operations that invalidate +page cache contents. Usually the filesystem needs to call +truncate_inode_pages_range() to invalidate relevant range of the page cache. +However the filesystem usually also needs to update its internal (and on disk) +view of file offset -> disk block mapping. Until this update is finished, the +filesystem needs to block page faults and reads from reloading now-stale page +cache contents from the disk. Since VFS acquires mapping->invalidate_lock in +shared mode when loading pages from disk (filemap_fault(), filemap_read(), +readahead paths), the fallocate implementation must take the invalidate_lock to +prevent reloading. + +->copy_file_range and ->remap_file_range implementations need to serialize +against modifications of file data while the operation is running. For +blocking changes through write(2) and similar operations inode->i_rwsem can be +used. To block changes to file contents via a memory mapping during the +operation, the filesystem must take mapping->invalidate_lock to coordinate +with ->page_mkwrite. + dquot_operations ================ @@ -630,11 +652,11 @@ pfn_mkwrite: yes access: yes ============= ========= =========================== -->fault() is called when a previously not present pte is about -to be faulted in. The filesystem must find and return the page associated -with the passed in "pgoff" in the vm_fault structure. If it is possible that -the page may be truncated and/or invalidated, then the filesystem must lock -the page, then ensure it is not already truncated (the page lock will block +->fault() is called when a previously not present pte is about to be faulted +in. The filesystem must find and return the page associated with the passed in +"pgoff" in the vm_fault structure. If it is possible that the page may be +truncated and/or invalidated, then the filesystem must lock invalidate_lock, +then ensure the page is not already truncated (invalidate_lock will block subsequent truncate), and then return with VM_FAULT_LOCKED, and the page locked. The VM will unlock the page. @@ -647,12 +669,14 @@ page table entry. Pointer to entry associated with the page is passed in "pte" field in vm_fault structure. Pointers to entries for other offsets should be calculated relative to "pte". -->page_mkwrite() is called when a previously read-only pte is -about to become writeable. The filesystem again must ensure that there are -no truncate/invalidate races, and then return with the page locked. If -the page has been truncated, the filesystem should not look up a new page -like the ->fault() handler, but simply return with VM_FAULT_NOPAGE, which -will cause the VM to retry the fault. +->page_mkwrite() is called when a previously read-only pte is about to become +writeable. The filesystem again must ensure that there are no +truncate/invalidate races or races with operations such as ->remap_file_range +or ->copy_file_range, and then return with the page locked. Usually +mapping->invalidate_lock is suitable for proper serialization. If the page has +been truncated, the filesystem should not look up a new page like the ->fault() +handler, but simply return with VM_FAULT_NOPAGE, which will cause the VM to +retry the fault. ->pfn_mkwrite() is the same as page_mkwrite but when the pte is VM_PFNMAP or VM_MIXEDMAP with a page-less entry. Expected return is diff --git a/fs/inode.c b/fs/inode.c index c93500d84264..84c528cd1955 100644 --- a/fs/inode.c +++ b/fs/inode.c @@ -190,6 +190,8 @@ int inode_init_always(struct super_block *sb, struct inode *inode) mapping_set_gfp_mask(mapping, GFP_HIGHUSER_MOVABLE); mapping->private_data = NULL; mapping->writeback_index = 0; + __init_rwsem(&mapping->invalidate_lock, "mapping.invalidate_lock", + &sb->s_type->invalidate_lock_key); inode->i_private = NULL; inode->i_mapping = mapping; INIT_HLIST_HEAD(&inode->i_dentry); /* buggered by rcu freeing */ diff --git a/include/linux/fs.h b/include/linux/fs.h index 640574294216..90a80de37ad4 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -436,6 +436,10 @@ int pagecache_write_end(struct file *, struct address_space *mapping, * struct address_space - Contents of a cacheable, mappable object. * @host: Owner, either the inode or the block_device. * @i_pages: Cached pages. + * @invalidate_lock: Guards coherency between page cache contents and + * file offset->disk block mappings in the filesystem during invalidates. + * It is also used to block modification of page cache contents through + * memory mappings. * @gfp_mask: Memory allocation flags to use for allocating pages. * @i_mmap_writable: Number of VM_SHARED mappings. * @nr_thps: Number of THPs in the pagecache (non-shmem only). @@ -453,6 +457,7 @@ int pagecache_write_end(struct file *, struct address_space *mapping, struct address_space { struct inode *host; struct xarray i_pages; + struct rw_semaphore invalidate_lock; gfp_t gfp_mask; atomic_t i_mmap_writable; #ifdef CONFIG_READ_ONLY_THP_FOR_FS @@ -814,6 +819,33 @@ static inline void inode_lock_shared_nested(struct inode *inode, unsigned subcla down_read_nested(&inode->i_rwsem, subclass); } +static inline void filemap_invalidate_lock(struct address_space *mapping) +{ + down_write(&mapping->invalidate_lock); +} + +static inline void filemap_invalidate_unlock(struct address_space *mapping) +{ + up_write(&mapping->invalidate_lock); +} + +static inline void filemap_invalidate_lock_shared(struct address_space *mapping) +{ + down_read(&mapping->invalidate_lock); +} + +static inline int filemap_invalidate_trylock_shared( + struct address_space *mapping) +{ + return down_read_trylock(&mapping->invalidate_lock); +} + +static inline void filemap_invalidate_unlock_shared( + struct address_space *mapping) +{ + up_read(&mapping->invalidate_lock); +} + void lock_two_nondirectories(struct inode *, struct inode*); void unlock_two_nondirectories(struct inode *, struct inode*); @@ -2487,6 +2519,7 @@ struct file_system_type { struct lock_class_key i_lock_key; struct lock_class_key i_mutex_key; + struct lock_class_key invalidate_lock_key; struct lock_class_key i_mutex_dir_key; }; diff --git a/mm/filemap.c b/mm/filemap.c index acf20eca2fa4..f7f9b87d2cd0 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -77,7 +77,8 @@ * ->i_pages lock * * ->i_rwsem - * ->i_mmap_rwsem (truncate->unmap_mapping_range) + * ->invalidate_lock (acquired by fs in truncate path) + * ->i_mmap_rwsem (truncate->unmap_mapping_range) * * ->mmap_lock * ->i_mmap_rwsem @@ -85,7 +86,8 @@ * ->i_pages lock (arch-dependent flush_dcache_mmap_lock) * * ->mmap_lock - * ->lock_page (access_process_vm) + * ->invalidate_lock (filemap_fault) + * ->lock_page (filemap_fault, access_process_vm) * * ->i_rwsem (generic_perform_write) * ->mmap_lock (fault_in_pages_readable->do_page_fault) @@ -2368,20 +2370,30 @@ static int filemap_update_page(struct kiocb *iocb, { int error; + if (iocb->ki_flags & IOCB_NOWAIT) { + if (!filemap_invalidate_trylock_shared(mapping)) + return -EAGAIN; + } else { + filemap_invalidate_lock_shared(mapping); + } + if (!trylock_page(page)) { + error = -EAGAIN; if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_NOIO)) - return -EAGAIN; + goto unlock_mapping; if (!(iocb->ki_flags & IOCB_WAITQ)) { + filemap_invalidate_unlock_shared(mapping); put_and_wait_on_page_locked(page, TASK_KILLABLE); return AOP_TRUNCATED_PAGE; } error = __lock_page_async(page, iocb->ki_waitq); if (error) - return error; + goto unlock_mapping; } + error = AOP_TRUNCATED_PAGE; if (!page->mapping) - goto truncated; + goto unlock; error = 0; if (filemap_range_uptodate(mapping, iocb->ki_pos, iter, page)) @@ -2392,15 +2404,13 @@ static int filemap_update_page(struct kiocb *iocb, goto unlock; error = filemap_read_page(iocb->ki_filp, mapping, page); - if (error == AOP_TRUNCATED_PAGE) - put_page(page); - return error; -truncated: - unlock_page(page); - put_page(page); - return AOP_TRUNCATED_PAGE; + goto unlock_mapping; unlock: unlock_page(page); +unlock_mapping: + filemap_invalidate_unlock_shared(mapping); + if (error == AOP_TRUNCATED_PAGE) + put_page(page); return error; } @@ -2415,6 +2425,19 @@ static int filemap_create_page(struct file *file, if (!page) return -ENOMEM; + /* + * Protect against truncate / hole punch. Grabbing invalidate_lock here + * assures we cannot instantiate and bring uptodate new pagecache pages + * after evicting page cache during truncate and before actually + * freeing blocks. Note that we could release invalidate_lock after + * inserting the page into page cache as the locked page would then be + * enough to synchronize with hole punching. But there are code paths + * such as filemap_update_page() filling in partially uptodate pages or + * ->readpages() that need to hold invalidate_lock while mapping blocks + * for IO so let's hold the lock here as well to keep locking rules + * simple. + */ + filemap_invalidate_lock_shared(mapping); error = add_to_page_cache_lru(page, mapping, index, mapping_gfp_constraint(mapping, GFP_KERNEL)); if (error == -EEXIST) @@ -2426,9 +2449,11 @@ static int filemap_create_page(struct file *file, if (error) goto error; + filemap_invalidate_unlock_shared(mapping); pagevec_add(pvec, page); return 0; error: + filemap_invalidate_unlock_shared(mapping); put_page(page); return error; } @@ -2967,6 +2992,7 @@ vm_fault_t filemap_fault(struct vm_fault *vmf) pgoff_t max_off; struct page *page; vm_fault_t ret = 0; + bool mapping_locked = false; max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); if (unlikely(offset >= max_off)) @@ -2976,25 +3002,39 @@ vm_fault_t filemap_fault(struct vm_fault *vmf) * Do we have something in the page cache already? */ page = find_get_page(mapping, offset); - if (likely(page) && !(vmf->flags & FAULT_FLAG_TRIED)) { + if (likely(page)) { /* - * We found the page, so try async readahead before - * waiting for the lock. + * We found the page, so try async readahead before waiting for + * the lock. */ - fpin = do_async_mmap_readahead(vmf, page); - } else if (!page) { + if (!(vmf->flags & FAULT_FLAG_TRIED)) + fpin = do_async_mmap_readahead(vmf, page); + if (unlikely(!PageUptodate(page))) { + filemap_invalidate_lock_shared(mapping); + mapping_locked = true; + } + } else { /* No page in the page cache at all */ count_vm_event(PGMAJFAULT); count_memcg_event_mm(vmf->vma->vm_mm, PGMAJFAULT); ret = VM_FAULT_MAJOR; fpin = do_sync_mmap_readahead(vmf); retry_find: + /* + * See comment in filemap_create_page() why we need + * invalidate_lock + */ + if (!mapping_locked) { + filemap_invalidate_lock_shared(mapping); + mapping_locked = true; + } page = pagecache_get_page(mapping, offset, FGP_CREAT|FGP_FOR_MMAP, vmf->gfp_mask); if (!page) { if (fpin) goto out_retry; + filemap_invalidate_unlock_shared(mapping); return VM_FAULT_OOM; } } @@ -3014,8 +3054,20 @@ retry_find: * We have a locked page in the page cache, now we need to check * that it's up-to-date. If not, it is going to be due to an error. */ - if (unlikely(!PageUptodate(page))) + if (unlikely(!PageUptodate(page))) { + /* + * The page was in cache and uptodate and now it is not. + * Strange but possible since we didn't hold the page lock all + * the time. Let's drop everything get the invalidate lock and + * try again. + */ + if (!mapping_locked) { + unlock_page(page); + put_page(page); + goto retry_find; + } goto page_not_uptodate; + } /* * We've made it this far and we had to drop our mmap_lock, now is the @@ -3026,6 +3078,8 @@ retry_find: unlock_page(page); goto out_retry; } + if (mapping_locked) + filemap_invalidate_unlock_shared(mapping); /* * Found the page and have a reference on it. @@ -3056,6 +3110,7 @@ page_not_uptodate: if (!error || error == AOP_TRUNCATED_PAGE) goto retry_find; + filemap_invalidate_unlock_shared(mapping); return VM_FAULT_SIGBUS; @@ -3067,6 +3122,8 @@ out_retry: */ if (page) put_page(page); + if (mapping_locked) + filemap_invalidate_unlock_shared(mapping); if (fpin) fput(fpin); return ret | VM_FAULT_RETRY; @@ -3437,6 +3494,8 @@ out: * * If the page does not get brought uptodate, return -EIO. * + * The function expects mapping->invalidate_lock to be already held. + * * Return: up to date page on success, ERR_PTR() on failure. */ struct page *read_cache_page(struct address_space *mapping, @@ -3460,6 +3519,8 @@ EXPORT_SYMBOL(read_cache_page); * * If the page does not get brought uptodate, return -EIO. * + * The function expects mapping->invalidate_lock to be already held. + * * Return: up to date page on success, ERR_PTR() on failure. */ struct page *read_cache_page_gfp(struct address_space *mapping, diff --git a/mm/readahead.c b/mm/readahead.c index d589f147f4c2..41b75d76d36e 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -192,6 +192,7 @@ void page_cache_ra_unbounded(struct readahead_control *ractl, */ unsigned int nofs = memalloc_nofs_save(); + filemap_invalidate_lock_shared(mapping); /* * Preallocate as many pages as we will need. */ @@ -236,6 +237,7 @@ void page_cache_ra_unbounded(struct readahead_control *ractl, * will then handle the error. */ read_pages(ractl, &page_pool, false); + filemap_invalidate_unlock_shared(mapping); memalloc_nofs_restore(nofs); } EXPORT_SYMBOL_GPL(page_cache_ra_unbounded); diff --git a/mm/rmap.c b/mm/rmap.c index a8b01929ab2e..86471aacc54a 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -22,24 +22,25 @@ * * inode->i_rwsem (while writing or truncating, not reading or faulting) * mm->mmap_lock - * page->flags PG_locked (lock_page) * (see hugetlbfs below) - * hugetlbfs_i_mmap_rwsem_key (in huge_pmd_share) - * mapping->i_mmap_rwsem - * hugetlb_fault_mutex (hugetlbfs specific page fault mutex) - * anon_vma->rwsem - * mm->page_table_lock or pte_lock - * swap_lock (in swap_duplicate, swap_info_get) - * mmlist_lock (in mmput, drain_mmlist and others) - * mapping->private_lock (in __set_page_dirty_buffers) - * lock_page_memcg move_lock (in __set_page_dirty_buffers) - * i_pages lock (widely used) - * lruvec->lru_lock (in lock_page_lruvec_irq) - * inode->i_lock (in set_page_dirty's __mark_inode_dirty) - * bdi.wb->list_lock (in set_page_dirty's __mark_inode_dirty) - * sb_lock (within inode_lock in fs/fs-writeback.c) - * i_pages lock (widely used, in set_page_dirty, - * in arch-dependent flush_dcache_mmap_lock, - * within bdi.wb->list_lock in __sync_single_inode) + * mapping->invalidate_lock (in filemap_fault) + * page->flags PG_locked (lock_page) * (see hugetlbfs below) + * hugetlbfs_i_mmap_rwsem_key (in huge_pmd_share) + * mapping->i_mmap_rwsem + * hugetlb_fault_mutex (hugetlbfs specific page fault mutex) + * anon_vma->rwsem + * mm->page_table_lock or pte_lock + * swap_lock (in swap_duplicate, swap_info_get) + * mmlist_lock (in mmput, drain_mmlist and others) + * mapping->private_lock (in __set_page_dirty_buffers) + * lock_page_memcg move_lock (in __set_page_dirty_buffers) + * i_pages lock (widely used) + * lruvec->lru_lock (in lock_page_lruvec_irq) + * inode->i_lock (in set_page_dirty's __mark_inode_dirty) + * bdi.wb->list_lock (in set_page_dirty's __mark_inode_dirty) + * sb_lock (within inode_lock in fs/fs-writeback.c) + * i_pages lock (widely used, in set_page_dirty, + * in arch-dependent flush_dcache_mmap_lock, + * within bdi.wb->list_lock in __sync_single_inode) * * anon_vma->rwsem,mapping->i_mmap_rwsem (memory_failure, collect_procs_anon) * ->tasklist_lock diff --git a/mm/truncate.c b/mm/truncate.c index 0f9becee9789..44ad5e515140 100644 --- a/mm/truncate.c +++ b/mm/truncate.c @@ -412,7 +412,8 @@ EXPORT_SYMBOL(truncate_inode_pages_range); * @mapping: mapping to truncate * @lstart: offset from which to truncate * - * Called under (and serialised by) inode->i_rwsem. + * Called under (and serialised by) inode->i_rwsem and + * mapping->invalidate_lock. * * Note: When this function returns, there can be a page in the process of * deletion (inside __delete_from_page_cache()) in the specified range. Thus |