[PATCH v3 0/4] btrfs: basic refactor of btrfs_buffered_write()

Qu Wenruo
2020-08-25T05:48:21Z

This patchset will refactor btrfs_buffered_write() by:
- Extra the nrptrs calculation into one function
The main concern here is the batch number of pages.
Originally there is a max(nrptrs, 8), which looks so incorrect that my
eyes change it to min(nrptrs, 8) automatically.

This time we kill that max(nrptrs, 8), and replace it to a fixed size
up limit (64K), which should bring the same performance for different
page sized.

The limit can be changed if the 64K is not large enough for certain
buffered write.

- Refactor the main loop into process_one_batch()
No functional change, just plain refactor.

- Remove the again: tag by integrating page and extent locking
The new function lock_pages_and_extent() will handle the retry so we
don't need the tag any more in the main loop.

Changelog:
v2:
- Fix a bug that ENOSPC error is not returned to user space
It's caused by a missing assignment for (copied < 0) branch in the 2nd
patch.

v3:
- Rename get_nr_pages() to calc_nr_pages()
- Remove unnecessary parameter for calc_nr_pages()
- Change the upper limit of calc_nr_pages() in a separate patch

Qu Wenruo (4):
btrfs: refactor @nrptrs calculation of btrfs_buffered_write()
btrfs: refactor btrfs_buffered_write() into process_one_batch()
btrfs: remove the again: tag in process_one_batch()
btrfs: avoid allocating unnecessary page pointers

fs/btrfs/file.c | 572 ++++++++++++++++++++++++++----------------------
1 file changed, 305 insertions(+), 267 deletions(-)

--
2.28.0