Commit:     ed2f2f9b3ff8debdf512f7687b232c3c1d7d60d7
Parent:     6967614761fd305b3414d9485d89dc2e0a407410
Author:     Mark Fasheh <[EMAIL PROTECTED]>
AuthorDate: Thu Jul 19 01:47:01 2007 -0700
Committer:  Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Thu Jul 19 10:04:41 2007 -0700

    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
    Signed-off-by: Mark Fasheh <[EMAIL PROTECTED]>
    Cc: Nick Piggin <[EMAIL PROTECTED]>
    Cc: David Howells <[EMAIL PROTECTED]>
    Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
    Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
 Documentation/filesystems/Locking |   11 ++++++++++-
 1 files changed, 10 insertions(+), 1 deletions(-)

diff --git a/Documentation/filesystems/Locking 
index 970c8ec..91ec4b4 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
                        Dubious stuff
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