Commit 09d91cda authored by Song Liu's avatar Song Liu Committed by Linus Torvalds
Browse files

mm,thp: avoid writes to file with THP in pagecache 

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 file is open for write.  A new counter nr_thps is added to struct
address_space.  In do_dentry_open(), if the file is open for write and
nr_thps is non-zero, we drop page cache for the whole file.

Link: http://lkml.kernel.org/r/20190801184244.3169074-8-songliubraving@fb.com


Signed-off-by: default avatarSong Liu <songliubraving@fb.com>
Reported-by: default avatarkbuild test robot <lkp@intel.com>
Acked-by: default avatarRik van Riel <riel@surriel.com>
Acked-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: William Kucharski <william.kucharski@oracle.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 99cb0dbd

fs/inode.c

+3 −0
Original line number Diff line number Diff line
@@ -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;

fs/open.c

+8 −0
Original line number Diff line number Diff line
@@ -818,6 +818,14 @@ static int do_dentry_open(struct file *f, 
		if (!f->f_mapping->a_ops || !f->f_mapping->a_ops->direct_IO)

			return -EINVAL;

	}



	/*

	 * XXX: Huge page cache doesn't support writing yet. Drop all page

	 * cache for this file before processing writes.

	 */

	if ((f->f_mode & FMODE_WRITE) && filemap_nr_thps(inode->i_mapping))

		truncate_pagecache(inode, 0);



	return 0;



cleanup_all:

include/linux/fs.h

+32 −0
Original line number Diff line number Diff line
@@ -429,6 +429,7 @@ int pagecache_write_end(struct file *, struct address_space *mapping, 
 * @i_pages: Cached pages.

 * @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).

 * @i_mmap: Tree of private and shared mappings.

 * @i_mmap_rwsem: Protects @i_mmap and @i_mmap_writable.

 * @nrpages: Number of page entries, protected by the i_pages lock.
@@ -446,6 +447,10 @@ 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;
@@ -2798,6 +2803,33 @@ 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);

mm/filemap.c

+1 −0
Original line number Diff line number Diff line
@@ -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);

	}



	/*

mm/khugepaged.c

+3 −1
Original line number Diff line number Diff line
@@ -1514,8 +1514,10 @@ out_unlock: 


	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);

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