On Tue, Apr 23, 2019 at 9:51 AM Murphy Zhou <jencce.kernel@xxxxxxxxx> wrote: > > Overlays ovl_iter_write calls vfs_iter_write to write on real file, > in which calls fsnotify_modify on this change, however vfs_write also > calls fsnotify_modify after ovl_iter_write. The first notification > sent by vfs_iter_write grabs marks from upper inode and overlay mnt, > because of its fake path. The second one sent by vfs_write grabs marks > from ovl inode and ovl mnt. > > LTP fanotify06 add modify mark for mnt point, then add ignore modify > mask on testfile, then truncate and write the file. Because the ignore > mask is marked on ovl inode, not the upper inode, the first event is not > masked like the second one. So we get a modification event even with a > mask on the file. Care to extend fanotify06 in a similar manner to the way readahead02 was extended to test overlay test case regardless of the base LTP filesystem? > > Proposing fixing this by add a new RWF flag to skip fsnotify on this IO. > vfs_iter_write used by ovl can use this flag to skip one duplicate event. > This fix is wrong for several reasons: - It exports RWF_NONOTIFY to uapi - It will cause no events at all when overlay writes to file even when user requested events on upper inode Please try attached patch. Thanks, Amir. > Signed-off-by: Murphy Zhou <jencce.kernel@xxxxxxxxx> > --- > fs/overlayfs/file.c | 2 +- > fs/read_write.c | 2 +- > include/uapi/linux/fs.h | 5 ++++- > 3 files changed, 6 insertions(+), 3 deletions(-) > > diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c > index 84dd957efa24..0827199a5311 100644 > --- a/fs/overlayfs/file.c > +++ b/fs/overlayfs/file.c > @@ -242,7 +242,7 @@ static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter) > old_cred = ovl_override_creds(file_inode(file)->i_sb); > file_start_write(real.file); > ret = vfs_iter_write(real.file, iter, &iocb->ki_pos, > - ovl_iocb_to_rwf(iocb)); > + ovl_iocb_to_rwf(iocb)|RWF_NONOTIFY); > file_end_write(real.file); > revert_creds(old_cred); > > diff --git a/fs/read_write.c b/fs/read_write.c > index 61b43ad7608e..aec751cacedf 100644 > --- a/fs/read_write.c > +++ b/fs/read_write.c > @@ -957,7 +957,7 @@ static ssize_t do_iter_write(struct file *file, struct iov_iter *iter, > ret = do_iter_readv_writev(file, iter, pos, WRITE, flags); > else > ret = do_loop_readv_writev(file, iter, pos, WRITE, flags); > - if (ret > 0) > + if (ret > 0 && !(flags & RWF_NONOTIFY)) > fsnotify_modify(file); > return ret; > } > diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h > index 121e82ce296b..103f1a9375f2 100644 > --- a/include/uapi/linux/fs.h > +++ b/include/uapi/linux/fs.h > @@ -342,8 +342,11 @@ typedef int __bitwise __kernel_rwf_t; > /* per-IO O_APPEND */ > #define RWF_APPEND ((__force __kernel_rwf_t)0x00000010) > > +/* do not notify this IO */ > +#define RWF_NONOTIFY ((__force __kernel_rwf_t)0x00000020) > + > /* mask of flags supported by the kernel */ > #define RWF_SUPPORTED (RWF_HIPRI | RWF_DSYNC | RWF_SYNC | RWF_NOWAIT |\ > - RWF_APPEND) > + RWF_APPEND | RWF_NONOTIFY) > > #endif /* _UAPI_LINUX_FS_H */ > -- > 2.21.0 >
From c511a103ba6690cbf6748f25700cb8e95dd77982 Mon Sep 17 00:00:00 2001 From: Amir Goldstein <amir73il@xxxxxxxxx> Date: Tue, 23 Apr 2019 13:11:10 +0300 Subject: [PATCH] ovl: use real path for open_with_fake_path() ovl_open() uses open_with_fake_path() to create a file object with a given path. Currently overlayfs uses the overlay path as the "fake" path. This causes some issues when VFS code refers to file->f_path->mnt. One issue, reported by Murphy Zhou, is that fsnotify hooks check for mount marks against the wrong vfsmount. Link: https://lore.kernel.org/linux-fsdevel/20190423065024.12695-1-jencce.kernel@xxxxxxxxx/ Reported-by: Murphy Zhou <jencce.kernel@xxxxxxxxx> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx> --- fs/overlayfs/file.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c index ddfd93f13cc5..ec9f8763fe08 100644 --- a/fs/overlayfs/file.c +++ b/fs/overlayfs/file.c @@ -28,10 +28,13 @@ static struct file *ovl_open_realfile(const struct file *file, { struct inode *inode = file_inode(file); struct file *realfile; + struct path realpath; const struct cred *old_cred; + ovl_path_real(file_dentry(file), &realpath); + old_cred = ovl_override_creds(inode->i_sb); - realfile = open_with_fake_path(&file->f_path, file->f_flags | O_NOATIME, + realfile = open_with_fake_path(&realpath, file->f_flags | O_NOATIME, realinode, current_cred()); revert_creds(old_cred); -- 2.17.1
