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authorSong Liu <songliubraving@fb.com>2019-09-23 15:38:03 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2019-09-24 15:54:11 -0700
commit09d91cda0e8207c1f14ee0d572f61a53dbcdaf85 (patch)
tree31686dc913d6904f0de79cecf644aa44e0cb49fc /fs
parent99cb0dbd47a15d395bf3faa78dc122bc5efe3fc0 (diff)
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: Song Liu <songliubraving@fb.com> Reported-by: kbuild test robot <lkp@intel.com> Acked-by: Rik van Riel <riel@surriel.com> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Acked-by: Johannes 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: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs')
-rw-r--r--fs/inode.c3
-rw-r--r--fs/open.c8
2 files changed, 11 insertions, 0 deletions
diff --git a/fs/inode.c b/fs/inode.c
index 64bf28cf05cd..fef457a42882 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/fs/open.c b/fs/open.c
index a59abe3c669a..c60cd22cc052 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -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:

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