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authorMark Fasheh <mark.fasheh@oracle.com>2007-07-19 01:47:01 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-07-19 10:04:41 -0700
commited2f2f9b3ff8debdf512f7687b232c3c1d7d60d7 (patch)
treef935333e6d233ba0f119d4642b15063ba544fddf
parent6967614761fd305b3414d9485d89dc2e0a407410 (diff)
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>
-rw-r--r--Documentation/filesystems/Locking11
1 files changed, 10 insertions, 1 deletions
diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
index 970c8ec1a05b..91ec4b40ebfe 100644
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -512,13 +512,22 @@ prototypes:
void (*close)(struct vm_area_struct*);
struct page *(*fault)(struct vm_area_struct*, struct fault_data *);
struct page *(*nopage)(struct vm_area_struct*, unsigned long, int *);
+ int (*page_mkwrite)(struct vm_area_struct *, struct page *);
locking rules:
- BKL mmap_sem
+ BKL mmap_sem PageLocked(page)
open: no yes
close: no yes
fault: no yes
nopage: no yes
+page_mkwrite: no yes no
+
+ ->page_mkwrite() is called when a previously read-only page is
+about to become writeable. The file system is responsible for
+protecting against truncate races. Once appropriate action has been
+taking to lock out truncate, the page range should be verified to be
+within i_size. The page mapping should also be checked that it is not
+NULL.
================================================================================
Dubious stuff