[v2,0/4] Stash overlay real upper file in backing_file

Message

Amir Goldstein Oct. 6, 2024, 8:23 a.m. UTC

Hi all,

This is v2 of the code to avoid temporary backing file opens in
overlayfs, taking into account Al's comments on v1 [1].

Miklos,

The implementation of ovl_real_file_path() helper is roughly based on
ovl_real_dir_file().

do you see any problems with this approach or any races not handled?
Note that I did have a logical bug in v1 (always choosing the stashed
upperfile if it exists), so there may be more.

Thanks,
Amir.

Changes since v1:
- Use helpers ovl_real_file() and ovl_upper_file() to express that
  ovl_real_file() cannot return NULL
- Fix readability and bug is code to select and store stashed upperfile

[1] https://lore.kernel.org/linux-fsdevel/[e-mail]/

Amir Goldstein (4):
  ovl: do not open non-data lower file for fsync
  ovl: stash upper real file in backing_file struct
  ovl: convert ovl_real_fdget_path() callers to ovl_real_file_path()
  ovl: convert ovl_real_fdget() callers to ovl_real_file()

 fs/file_table.c     |   7 ++
 fs/internal.h       |   6 +
 fs/overlayfs/file.c | 288 ++++++++++++++++++++++++++------------------
 3 files changed, 182 insertions(+), 119 deletions(-)