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documentation: document the is_dirty_writeback aops callback 

Signed-off-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Mel Gorman 2013-07-03 15:04:46 -07:00 committed by Linus Torvalds
parent 26c0c5bf38
commit 543cc11533
1 changed files with 10 additions and 0 deletions
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10
Documentation/filesystems/vfs.txt
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@ -582,6 +582,7 @@ struct address_space_operations {
int (*launder_page) (struct page *);
int (*is_partially_uptodate) (struct page *, read_descriptor_t *,
unsigned long);
void (*is_dirty_writeback) (struct page *, bool *, bool *);
int (*error_remove_page) (struct mapping *mapping, struct page *page);
int (*swap_activate)(struct file *);
int (*swap_deactivate)(struct file *);
@ -746,6 +747,15 @@ struct address_space_operations {
block is up to date then the read can complete without needing the IO
to bring the whole page up to date.
is_dirty_writeback: Called by the VM when attempting to reclaim a page.
The VM uses dirty and writeback information to determine if it needs
to stall to allow flushers a chance to complete some IO. Ordinarily
it can use PageDirty and PageWriteback but some filesystems have
more complex state (unstable pages in NFS prevent reclaim) or
do not set those flags due to locking problems (jbd). This callback
allows a filesystem to indicate to the VM if a page should be
treated as dirty or writeback for the purposes of stalling.
error_remove_page: normally set to generic_error_remove_page if truncation
is ok for this address space. Used for memory failure handling.
Setting this implies you deal with pages going away under you,