Commit ed2f2f9b3ff8debdf512f7687b232c3c1d7d60d7
Committed by
Linus Torvalds
Linus Torvalds
1 parent
6967614761
Document ->page_mkwrite() locking
There seems to be very little documentation about this callback in general. The locking in particular is a bit tricky, so it's worth having this in writing. Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Cc: David Howells <dhowells@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Showing 1 changed file with 10 additions and 1 deletions Side-by-side Diff
Documentation/filesystems/Locking
| ... | ... | @@ -512,13 +512,22 @@ |
| 512 | 512 | void (*close)(struct vm_area_struct*); |
| 513 | 513 | struct page *(*fault)(struct vm_area_struct*, struct fault_data *); |
| 514 | 514 | struct page *(*nopage)(struct vm_area_struct*, unsigned long, int *); |
| 515 | + int (*page_mkwrite)(struct vm_area_struct *, struct page *); | |
| 515 | 516 | |
| 516 | 517 | locking rules: |
| 517 | - BKL mmap_sem | |
| 518 | + BKL mmap_sem PageLocked(page) | |
| 518 | 519 | open: no yes |
| 519 | 520 | close: no yes |
| 520 | 521 | fault: no yes |
| 521 | 522 | nopage: no yes |
| 523 | +page_mkwrite: no yes no | |
| 524 | + | |
| 525 | + ->page_mkwrite() is called when a previously read-only page is | |
| 526 | +about to become writeable. The file system is responsible for | |
| 527 | +protecting against truncate races. Once appropriate action has been | |
| 528 | +taking to lock out truncate, the page range should be verified to be | |
| 529 | +within i_size. The page mapping should also be checked that it is not | |
| 530 | +NULL. | |
| 522 | 531 | |
| 523 | 532 | ================================================================================ |
| 524 | 533 | Dubious stuff |