[PATCH v2 0/7] exfat: fix valid_size update races

[Chi Zhiling <chizhiling@163.com>]

From: Chi Zhiling <chizhiling@kylinos.cn>

exFAT uses valid_size (ValidDataLength) as the on-disk boundary of
initialised data, but the current code advances it too late or without
proper serialisation.  As a result, buffered writes can silently lose
data reclaimed before valid_size covers it, page faults and direct I/O
can race with writes, and a failed direct write still grows the file
on disk.

This series advances valid_size under the folio lock for buffered
writes, revalidates cached iomaps, drops i_rwsem from
exfat_page_mkwrite(), and publishes i_size/valid_size only on
successful direct I/O completion.

V1: https://lore.kernel.org/exfat/59056131-e3bd-4003-8c30-0a356cf0bd82@163.com/
Link: https://lore.kernel.org/exfat/10029d6f-13cc-4d17-a2f9-b093a8339dde/T/#t

Chi Zhiling (7):
  exfat: advance valid_size under the folio lock for buffered writes
  exfat: advance valid_size while zeroing new ranges
  exfat: validate cached iomaps during buffered writes
  exfat: drop i_rwsem from exfat_page_mkwrite
  exfat: do not re-zero the valid range in exfat_page_mkwrite
  exfat: complete direct writes synchronously when they update metadata
  exfat: publish i_size and valid_size on direct I/O completion

 fs/exfat/file.c  | 69 ++++++++++++++++++++++---------------
 fs/exfat/iomap.c | 88 +++++++++++++++++++++++++++++++++++++++---------
 fs/exfat/iomap.h |  1 +
 3 files changed, 114 insertions(+), 44 deletions(-)

-- 
2.53.0