linux-ext4 - [PATCH v2 0/2] Document handing of unwritten bh in ext4_block_zero_page

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Message-Id: <cover.1698856309.git.ojaswin@linux.ibm.com>
Date:   Wed,  1 Nov 2023 22:08:09 +0530
From:   Ojaswin Mujoo <ojaswin@...ux.ibm.com>
To:     linux-ext4@...r.kernel.org, "Theodore Ts'o" <tytso@....edu>
Cc:     Ritesh Harjani <ritesh.list@...il.com>,
        linux-kernel@...r.kernel.org, Jan Kara <jack@...e.cz>
Subject: [PATCH v2 0/2] Document handing of unwritten bh in ext4_block_zero_page_range()

** Changes v1 -> v2 **

* Instead of exiting early in ext4_block_zero_page_range() for unwrit
  bhs like in v1, lets let the current logic be as it is and instead
  document the handing of unwritten buffer heads to make the intent
  clear

v1:
https://lore.kernel.org/linux-ext4/20231019165546.norapdphdyx7g3ob@quack3/T/#mbd0ab69d55487493edbd465b3882051e5bc2365d

** Original Cover Letter **

As per discussion with Jan here [1], this patchset intends to exit early
from __ext4_block_zero_page_range() incase the block we are about to
zero (partially) is unwritten and unmapped, since such a block doesn't
require zeroing.

Further, also make sure that calls to ext4_zero_partial_blocks()
truncate the page cache completely beforehand, so that they don't rely
on ext4_zero_partial_block() -> __ext4_block_zero_page_range() to zero
out non block aligned edges of pagecache.

Reviews and comments are appreciated!

Regards,
ojaswin

[1]
https://lore.kernel.org/linux-ext4/20230914141920.lw2nlpzhcxwuz2y6@quack3/

Ojaswin Mujoo (2):
  ext4: treat end of range as exclusive in ext4_zero_range()
  ext4: Clarify handling of unwritten bh in
    __ext4_block_zero_page_range()

 fs/ext4/extents.c | 6 ++++--
 fs/ext4/inode.c   | 6 ++++++
 2 files changed, 10 insertions(+), 2 deletions(-)

-- 
2.39.3