In previous patch, an application could put part of its text section in THP via madvise(). These THPs will be protected from writes when the application is still running (TXTBSY). However, after the application exits, the file is available for writes.
This patch avoids writes to file THP by dropping page cache for the file when the last vma with VM_DENYWRITE is removed. A new counter nr_thps is added to struct address_space. In exit_mmap(), if nr_thps is non-zero, we drop page cache for the whole file. Signed-off-by: Song Liu <[email protected]> --- fs/inode.c | 3 +++ include/linux/fs.h | 31 +++++++++++++++++++++++++++++++ mm/filemap.c | 1 + mm/khugepaged.c | 4 +++- mm/mmap.c | 14 ++++++++++++++ 5 files changed, 52 insertions(+), 1 deletion(-) diff --git a/fs/inode.c b/fs/inode.c index df6542ec3b88..518113a4e219 100644 --- a/fs/inode.c +++ b/fs/inode.c @@ -181,6 +181,9 @@ int inode_init_always(struct super_block *sb, struct inode *inode) mapping->flags = 0; mapping->wb_err = 0; atomic_set(&mapping->i_mmap_writable, 0); +#ifdef CONFIG_READ_ONLY_THP_FOR_FS + atomic_set(&mapping->nr_thps, 0); +#endif mapping_set_gfp_mask(mapping, GFP_HIGHUSER_MOVABLE); mapping->private_data = NULL; mapping->writeback_index = 0; diff --git a/include/linux/fs.h b/include/linux/fs.h index f7fdfe93e25d..3edf4ee42eee 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -444,6 +444,10 @@ struct address_space { struct xarray i_pages; gfp_t gfp_mask; atomic_t i_mmap_writable; +#ifdef CONFIG_READ_ONLY_THP_FOR_FS + /* number of thp, only for non-shmem files */ + atomic_t nr_thps; +#endif struct rb_root_cached i_mmap; struct rw_semaphore i_mmap_rwsem; unsigned long nrpages; @@ -2790,6 +2794,33 @@ static inline errseq_t filemap_sample_wb_err(struct address_space *mapping) return errseq_sample(&mapping->wb_err); } +static inline int filemap_nr_thps(struct address_space *mapping) +{ +#ifdef CONFIG_READ_ONLY_THP_FOR_FS + return atomic_read(&mapping->nr_thps); +#else + return 0; +#endif +} + +static inline void filemap_nr_thps_inc(struct address_space *mapping) +{ +#ifdef CONFIG_READ_ONLY_THP_FOR_FS + atomic_inc(&mapping->nr_thps); +#else + WARN_ON_ONCE(1); +#endif +} + +static inline void filemap_nr_thps_dec(struct address_space *mapping) +{ +#ifdef CONFIG_READ_ONLY_THP_FOR_FS + atomic_dec(&mapping->nr_thps); +#else + WARN_ON_ONCE(1); +#endif +} + extern int vfs_fsync_range(struct file *file, loff_t start, loff_t end, int datasync); extern int vfs_fsync(struct file *file, int datasync); diff --git a/mm/filemap.c b/mm/filemap.c index e79ceccdc6df..a8e86c136381 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -205,6 +205,7 @@ static void unaccount_page_cache_page(struct address_space *mapping, __dec_node_page_state(page, NR_SHMEM_THPS); } else if (PageTransHuge(page)) { __dec_node_page_state(page, NR_FILE_THPS); + filemap_nr_thps_dec(mapping); } /* diff --git a/mm/khugepaged.c b/mm/khugepaged.c index fbcff5a1d65a..17ebe9da56ce 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1500,8 +1500,10 @@ static void collapse_file(struct vm_area_struct *vma, if (is_shmem) __inc_node_page_state(new_page, NR_SHMEM_THPS); - else + else { __inc_node_page_state(new_page, NR_FILE_THPS); + filemap_nr_thps_inc(mapping); + } if (nr_none) { struct zone *zone = page_zone(new_page); diff --git a/mm/mmap.c b/mm/mmap.c index 7e8c3e8ae75f..8094ce028d74 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -3088,6 +3088,18 @@ int vm_brk(unsigned long addr, unsigned long len) } EXPORT_SYMBOL(vm_brk); +static inline void release_file_thp(struct vm_area_struct *vma) +{ +#ifdef CONFIG_READ_ONLY_THP_FOR_FS + struct file *file = vma->vm_file; + + if (file && (vma->vm_flags & VM_DENYWRITE) && + atomic_read(&file_inode(file)->i_writecount) == 0 && + filemap_nr_thps(file_inode(file)->i_mapping)) + truncate_pagecache(file_inode(file), 0); +#endif +} + /* Release all mmaps. */ void exit_mmap(struct mm_struct *mm) { @@ -3153,6 +3165,8 @@ void exit_mmap(struct mm_struct *mm) while (vma) { if (vma->vm_flags & VM_ACCOUNT) nr_accounted += vma_pages(vma); + + release_file_thp(vma); vma = remove_vma(vma); } vm_unacct_memory(nr_accounted); -- 2.17.1
