SB_START_PAGEFAULT(9)                     The Linux VFS                     SB_START_PAGEFAULT(9)



NAME
       sb_start_pagefault - get write access to a superblock from a page fault

SYNOPSIS
       void sb_start_pagefault(struct super_block * sb);

ARGUMENTS
       sb
           the super we write to

DESCRIPTION
       When a process starts handling write page fault, it should embed the operation into
       sb_start_pagefault - sb_end_pagefault pair to get exclusion against file system freezing.
       This is needed since the page fault is going to dirty a page. This function increments
       number of running page faults preventing freezing. If the file system is already frozen,
       the function waits until the file system is thawed.

       Since page fault freeze protection behaves as a lock, users have to preserve ordering of
       freeze protection and other filesystem locks. It is advised to put sb_start_pagefault
       close to mmap_sem in lock ordering. Page fault handling code implies lock dependency:

       mmap_sem -> sb_start_pagefault

COPYRIGHT
Kernel Hackers Manual 4.8.                 January 2017                     SB_START_PAGEFAULT(9)