[PATCH 0/2] Avert possible deadlock with splice() and fanotify

[Amir Goldstein <amir73il@gmail.com>]

Christian,

Josef has helped me see the light and figure out how to avoid the
possible deadlock, which involves:
- splice() from source file in a loop mounted fs to dest file in
  a host fs, where the loop image file is
- fsfreeze on host fs
- write to host fs in context of fanotify permission event handler
  (FAN_ACCESS_PERM) on the splice source file

The first patch should not be changing any logic.
I only build tested the ceph patch, so hoping to get an
Acked-by/Tested-by from Jeff.

The second patch rids us of the deadlock by not holding
file_start_write() while reading from splice source file.

The patches apply and tested on top of vfs.rw branch.

Thanks,
Amir.

Amir Goldstein (2):
  fs: fork do_splice_copy_file_range() from do_splice_direct()
  fs: move file_start_write() into direct_splice_actor()

 fs/ceph/file.c         |  9 +++--
 fs/overlayfs/copy_up.c |  2 -
 fs/read_write.c        |  8 +---
 fs/splice.c            | 88 +++++++++++++++++++++++++++++++-----------
 include/linux/fs.h     |  2 -
 include/linux/splice.h | 13 ++++---
 6 files changed, 81 insertions(+), 41 deletions(-)

-- 
2.34.1