f2fs: remove mappedtodisk flag usage in mmap write path

PG_mappedtodisk was inherited from the nobh/buffer-head era.  However,
f2fs has no buffer heads and the flag is no longer meaningful.  The only
user of the flag is the "no holes" shortcut in f2fs_vm_page_mkwrite(),
which makes mmap write faults skip marking the folio dirty.  Moreover,
it causes the following race condition with filesystem freezing:

 CPU0 (write fault)     CPU1 (freeze_super)
 ----                   ----
 f2fs_vm_page_mkwrite()
 sb_start_pagefault()
 /* shortcut: no dirty */
 sb_end_pagefault()

                        sb_wait_write(SB_FREEZE_PAGEFAULT)
                        /* no waiter, passes */
                        sync_filesystem()
                        /* folio not dirty, skipped */

 finish_fault()
 /* PTE writable */
 fault_dirty_shared_page()
 folio_mark_dirty()
 /* dirty folio on a frozen fs */

It will also skip APP_MAPPED_IO iostat/REQ_TIME updates and post-EOF
folio zeroing.

Remove this shortcut in f2fs_vm_page_mkwrite() and stop setting it in
f2fs_read_single_page().

Reported-by: Chao Yu <chao@kernel.org>
Link: https://lore.kernel.org/linux-f2fs-devel/496b913c-eb81-4fa8-be72-c6a06a10aba2@kernel.org/
Reviewed-by: Chao Yu <chao@kernel.org>
Reviewed-by: Barry Song <baohua@kernel.org>
Fixes: fbfa2cc58d53 ("f2fs: add file operations")
Cc: stable@vger.kernel.org
Signed-off-by: Nanzhe Zhao <zhaonanzhe@xiaomi.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

0 files changed, 0 insertions, 0 deletions