We have use cases where we want to trigger readahead in preadv2(2) with
RWF_NOWAIT set [0].
Readahead support was originally added for IOCB_NOWAIT in commit
2e85abf053b9 ("mm: allow read-ahead with IOCB_NOWAIT set"). However, this
behavior was modified in commit efa8480a8316 ("fs: RWF_NOWAIT should imply
IOCB_NOIO") due to concerns about potential blocking during memory
reclamation.
To prevent blocking on memory reclamation, we can utilize
memalloc_nowait_{save,restore} to ensure non-blocking behavior. By
restoring the original behavior, we can allow preadv2(IOCB_NOWAIT) to read
data directly from disk if it's not already in the page cache.
Changes:
- fs: Add a new flag RWF_IOWAIT for preadv2(2)
https://lore.kernel.org/linux-fsdevel/20240804080251.21239-1-laoar.shao@xxxxxxxxx/ [0]
Yafang Shao (2):
mm: Add memalloc_nowait_{save,restore}
mm: allow read-ahead with IOCB_NOWAIT set
include/linux/fs.h | 1 -
include/linux/sched/mm.h | 30 ++++++++++++++++++++++++++++++
mm/filemap.c | 6 ++++++
3 files changed, 36 insertions(+), 1 deletion(-)
--
2.43.5
