[PATCH v1 0/2] mm: skip wait in wait_sb_inodes() for hangable-writeback mappings

[Joanne Koong <joannelkoong@gmail.com>]

As reported by Athul upstream in [1], there is a userspace regression caused
by commit 0c58a97f919c ("fuse: remove tmp folio for writebacks and internal rb
tree") where if there is a bug in a fuse server that causes the server to
never complete writeback, it will make wait_sb_inodes() wait forever, causing
sync paths to hang.

This is a resubmission of this patch [2] that was dropped from the original
series due to a buggy/malicious server still being able to hold up sync() /
the system in other ways if they wanted to, but the wait_sb_inodes() path is
particularly common and easier to hit for malfunctioning servers.

Thanks,
Joanne

[1] https://lore.kernel.org/regressions/CAJnrk1ZjQ8W8NzojsvJPRXiv9TuYPNdj8Ye7=Cgkj=iV_i8EaA@mail.gmail.com/T/#t
[2] https://lore.kernel.org/linux-fsdevel/20241122232359.429647-4-joannelkoong@gmail.com/

Joanne Koong (2):
  mm: rename AS_WRITEBACK_MAY_DEADLOCK_ON_RECLAIM to
    AS_WRITEBACK_MAY_HANG
  fs/writeback: skip inodes with potential writeback hang in
    wait_sb_inodes()

 fs/fs-writeback.c       |  3 +++
 fs/fuse/file.c          |  2 +-
 include/linux/pagemap.h | 10 +++++-----
 mm/vmscan.c             |  3 +--
 4 files changed, 10 insertions(+), 8 deletions(-)

-- 
2.47.3