lkml.org 
[lkml]   [2018]   [Jul]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 3/4] f2fs: fix avoid race between truncate and background GC
On 07/29, Chao Yu wrote:
> On 2018/7/29 9:58, Jaegeuk Kim wrote:
> > On 07/27, Chao Yu wrote:
> >> Thread A Background GC
> >> - f2fs_setattr isize to 0
> >> - truncate_setsize
> >> - gc_data_segment
> >> - f2fs_get_read_data_page page #0
> >> - set_page_dirty
> >> - set_cold_data
> >> - f2fs_truncate
> >>
> >> - f2fs_setattr isize to 4k
> >> - read 4k <--- hit data in cached page #0
> >>
> >> Above race condition can cause read out invalid data in a truncated
> >> page, fix it by i_gc_rwsem[WRITE] lock.
> >
> > We can truncate pages again after f2fs_truncate()?
>
> I think it can fix this issue, although it looks a little strange to truncate
> page cache twice.

It'd be fine to do setsize first, and drop the cache later.

>
> Thanks,
>
> >
> >>
> >> Signed-off-by: Chao Yu <yuchao0@huawei.com>
> >> ---
> >> fs/f2fs/data.c | 4 ++++
> >> fs/f2fs/file.c | 33 +++++++++++++++++++--------------
> >> 2 files changed, 23 insertions(+), 14 deletions(-)
> >>
> >> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> >> index 071224ded5f4..a29f3162b887 100644
> >> --- a/fs/f2fs/data.c
> >> +++ b/fs/f2fs/data.c
> >> @@ -2214,10 +2214,14 @@ static void f2fs_write_failed(struct address_space *mapping, loff_t to)
> >> loff_t i_size = i_size_read(inode);
> >>
> >> if (to > i_size) {
> >> + down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
> >> down_write(&F2FS_I(inode)->i_mmap_sem);
> >> +
> >> truncate_pagecache(inode, i_size);
> >> f2fs_truncate_blocks(inode, i_size, true);
> >> +
> >> up_write(&F2FS_I(inode)->i_mmap_sem);
> >> + up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
> >> }
> >> }
> >>
> >> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> >> index 7bd2412a8c37..ed5c9b0e0d0c 100644
> >> --- a/fs/f2fs/file.c
> >> +++ b/fs/f2fs/file.c
> >> @@ -796,22 +796,25 @@ int f2fs_setattr(struct dentry *dentry, struct iattr *attr)
> >> }
> >>
> >> if (attr->ia_valid & ATTR_SIZE) {
> >> - if (attr->ia_size <= i_size_read(inode)) {
> >> - down_write(&F2FS_I(inode)->i_mmap_sem);
> >> - truncate_setsize(inode, attr->ia_size);
> >> + bool to_smaller = (attr->ia_size <= i_size_read(inode));
> >> +
> >> + down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
> >> + down_write(&F2FS_I(inode)->i_mmap_sem);
> >> +
> >> + truncate_setsize(inode, attr->ia_size);
> >> +
> >> + if (to_smaller)
> >> err = f2fs_truncate(inode);
> >> - up_write(&F2FS_I(inode)->i_mmap_sem);
> >> - if (err)
> >> - return err;
> >> - } else {
> >> - /*
> >> - * do not trim all blocks after i_size if target size is
> >> - * larger than i_size.
> >> - */
> >> - down_write(&F2FS_I(inode)->i_mmap_sem);
> >> - truncate_setsize(inode, attr->ia_size);
> >> - up_write(&F2FS_I(inode)->i_mmap_sem);
> >> + /*
> >> + * do not trim all blocks after i_size if target size is
> >> + * larger than i_size.
> >> + */
> >> + up_write(&F2FS_I(inode)->i_mmap_sem);
> >> + up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
> >> + if (err)
> >> + return err;
> >>
> >> + if (!to_smaller) {
> >> /* should convert inline inode here */
> >> if (!f2fs_may_inline_data(inode)) {
> >> err = f2fs_convert_inline_inode(inode);
> >> @@ -958,6 +961,7 @@ static int punch_hole(struct inode *inode, loff_t offset, loff_t len)
> >>
> >> blk_start = (loff_t)pg_start << PAGE_SHIFT;
> >> blk_end = (loff_t)pg_end << PAGE_SHIFT;
> >> + down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
> >> down_write(&F2FS_I(inode)->i_mmap_sem);
> >> truncate_inode_pages_range(mapping, blk_start,
> >> blk_end - 1);
> >> @@ -966,6 +970,7 @@ static int punch_hole(struct inode *inode, loff_t offset, loff_t len)
> >> ret = f2fs_truncate_hole(inode, pg_start, pg_end);
> >> f2fs_unlock_op(sbi);
> >> up_write(&F2FS_I(inode)->i_mmap_sem);
> >> + up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
> >> }
> >> }
> >>
> >> --
> >> 2.18.0.rc1

\
 
 \ /
  Last update: 2018-07-29 08:15    [W:0.043 / U:1.688 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site