fs: introduce write_begin, write_end, and perform_write aops

These are intended to replace prepare_write and commit_write with more
flexible alternatives that are also able to avoid the buffered write
deadlock problems efficiently (which prepare_write is unable to do).

[mark.fasheh@oracle.com: API design contributions, code review and fixes]
[akpm@linux-foundation.org: various fixes]
[dmonakhov@sw.ru: new aop block_write_begin fix]
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
Signed-off-by: Dmitriy Monakhov <dmonakhov@openvz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 3 deletions

diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
index f0f825808ca4..fe26cc978523 100644
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -178,15 +178,18 @@ prototypes:
 locking rules:
         All except set_page_dirty may block
 
-                        BKL     PageLocked(page)
+                        BKL     PageLocked(page)        i_sem
 writepage:              no      yes, unlocks (see below)
 readpage:               no      yes, unlocks
 sync_page:              no      maybe
 writepages:             no
 set_page_dirty          no      no
 readpages:              no
-prepare_write:          no      yes
-commit_write:           no      yes
+prepare_write:          no      yes                     yes
+commit_write:           no      yes                     yes
+write_begin:            no      locks the page          yes
+write_end:              no      yes, unlocks            yes
+perform_write:          no      n/a                     yes
 bmap:                   yes
 invalidatepage:         no      yes
 releasepage:            no      yes