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 <yuch...@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