Messages in this thread | | | Date | Wed, 6 Jan 2021 14:28:52 -0800 | From | Jaegeuk Kim <> | Subject | Re: [PATCH v2] f2fs: fix to keep isolation of atomic write |
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Hi Chao,
With a quick test, this patch causes down_write failure resulting in blocking process. I didn't dig in the bug so, please check the code again. :P
On 12/30, Chao Yu wrote: > ThreadA ThreadB > - f2fs_ioc_start_atomic_write > - write > - f2fs_ioc_commit_atomic_write > - f2fs_commit_inmem_pages > - f2fs_drop_inmem_pages > - f2fs_drop_inmem_pages > - __revoke_inmem_pages > - f2fs_vm_page_mkwrite > - set_page_dirty > - tag ATOMIC_WRITTEN_PAGE and add page > to inmem_pages list > - clear_inode_flag(FI_ATOMIC_FILE) > - f2fs_vm_page_mkwrite > - set_page_dirty > - f2fs_update_dirty_page > - f2fs_trace_pid > - tag inmem page private to pid > - truncate > - f2fs_invalidate_page > - set page->mapping to NULL > then it will cause panic once we > access page->mapping > > The root cause is we missed to keep isolation of atomic write in the case > of commit_atomic_write vs mkwrite, let commit_atomic_write helds i_mmap_sem > lock to avoid this issue. > > Signed-off-by: Chao Yu <yuchao0@huawei.com> > --- > v2: > - use i_mmap_sem to avoid mkwrite racing with below flows: > * f2fs_ioc_start_atomic_write > * f2fs_drop_inmem_pages > * f2fs_commit_inmem_pages > > fs/f2fs/file.c | 3 +++ > fs/f2fs/segment.c | 7 +++++++ > 2 files changed, 10 insertions(+) > > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c > index 4e6d4b9120a8..a48ec650d691 100644 > --- a/fs/f2fs/file.c > +++ b/fs/f2fs/file.c > @@ -2050,6 +2050,7 @@ static int f2fs_ioc_start_atomic_write(struct file *filp) > goto out; > > down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > + down_write(&F2FS_I(inode)->i_mmap_sem); > > /* > * Should wait end_io to count F2FS_WB_CP_DATA correctly by > @@ -2060,6 +2061,7 @@ static int f2fs_ioc_start_atomic_write(struct file *filp) > inode->i_ino, get_dirty_pages(inode)); > ret = filemap_write_and_wait_range(inode->i_mapping, 0, LLONG_MAX); > if (ret) { > + up_write(&F2FS_I(inode)->i_mmap_sem); > up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > goto out; > } > @@ -2073,6 +2075,7 @@ static int f2fs_ioc_start_atomic_write(struct file *filp) > /* add inode in inmem_list first and set atomic_file */ > set_inode_flag(inode, FI_ATOMIC_FILE); > clear_inode_flag(inode, FI_ATOMIC_REVOKE_REQUEST); > + up_write(&F2FS_I(inode)->i_mmap_sem); > up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > > f2fs_update_time(F2FS_I_SB(inode), REQ_TIME); > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c > index d8570b0359f5..dab870d9faf6 100644 > --- a/fs/f2fs/segment.c > +++ b/fs/f2fs/segment.c > @@ -327,6 +327,8 @@ void f2fs_drop_inmem_pages(struct inode *inode) > struct f2fs_sb_info *sbi = F2FS_I_SB(inode); > struct f2fs_inode_info *fi = F2FS_I(inode); > > + down_write(&F2FS_I(inode)->i_mmap_sem); > + > while (!list_empty(&fi->inmem_pages)) { > mutex_lock(&fi->inmem_lock); > __revoke_inmem_pages(inode, &fi->inmem_pages, > @@ -344,6 +346,8 @@ void f2fs_drop_inmem_pages(struct inode *inode) > sbi->atomic_files--; > } > spin_unlock(&sbi->inode_lock[ATOMIC_FILE]); > + > + up_write(&F2FS_I(inode)->i_mmap_sem); > } > > void f2fs_drop_inmem_page(struct inode *inode, struct page *page) > @@ -467,6 +471,7 @@ int f2fs_commit_inmem_pages(struct inode *inode) > f2fs_balance_fs(sbi, true); > > down_write(&fi->i_gc_rwsem[WRITE]); > + down_write(&F2FS_I(inode)->i_mmap_sem); > > f2fs_lock_op(sbi); > set_inode_flag(inode, FI_ATOMIC_COMMIT); > @@ -478,6 +483,8 @@ int f2fs_commit_inmem_pages(struct inode *inode) > clear_inode_flag(inode, FI_ATOMIC_COMMIT); > > f2fs_unlock_op(sbi); > + > + up_write(&F2FS_I(inode)->i_mmap_sem); > up_write(&fi->i_gc_rwsem[WRITE]); > > return err; > -- > 2.29.2
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