sb_start_pagefault — get write access to a superblock from a page fault
void sb_start_pagefault ( | struct super_block * sb); |
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