X-Git-Url: http://ftp.safe.ca/?a=blobdiff_plain;f=Documentation%2Ffilesystems%2FLocking;h=18b9d0ca0630e281bb20dc5c5991e4b6f06b4643;hb=955234755ce4a2c33cfc558912aa8f2148cc1fc6;hp=76efe5b71d7d8f744739a129f4b5333b898acf5c;hpb=c2ec175c39f62949438354f603f4aa170846aabb;p=safe%2Fjmp%2Flinux-2.6

diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
index 76efe5b..18b9d0c 100644
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -109,27 +109,28 @@ prototypes:
 
 locking rules:
 	All may block.
-			BKL	s_lock	s_umount
-alloc_inode:		no	no	no
-destroy_inode:		no
-dirty_inode:		no				(must not sleep)
-write_inode:		no
-drop_inode:		no				!!!inode_lock!!!
-delete_inode:		no
-put_super:		yes	yes	no
-write_super:		no	yes	read
-sync_fs:		no	no	read
-freeze_fs:		?
-unfreeze_fs:		?
-statfs:			no	no	no
-remount_fs:		yes	yes	maybe		(see below)
-clear_inode:		no
-umount_begin:		yes	no	no
-show_options:		no				(vfsmount->sem)
-quota_read:		no	no	no		(see below)
-quota_write:		no	no	no		(see below)
-
-->remount_fs() will have the s_umount lock if it's already mounted.
+	None have BKL
+			s_umount
+alloc_inode:
+destroy_inode:
+dirty_inode:				(must not sleep)
+write_inode:
+drop_inode:				!!!inode_lock!!!
+delete_inode:
+put_super:		write
+write_super:		read
+sync_fs:		read
+freeze_fs:		read
+unfreeze_fs:		read
+statfs:			no
+remount_fs:		maybe		(see below)
+clear_inode:
+umount_begin:		no
+show_options:		no		(namespace_sem)
+quota_read:		no		(see below)
+quota_write:		no		(see below)
+
+->remount_fs() will have the s_umount exclusive lock if it's already mounted.
 When called from get_sb_single, it does NOT have the s_umount lock.
 ->quota_read() and ->quota_write() functions are both guaranteed to
 be the only ones operating on the quota file by the quota code (via
@@ -187,7 +188,7 @@ readpages:		no
 write_begin:		no	locks the page		yes
 write_end:		no	yes, unlocks		yes
 perform_write:		no	n/a			yes
-bmap:			yes
+bmap:			no
 invalidatepage:		no	yes
 releasepage:		no	yes
 direct_IO:		no
@@ -512,16 +513,24 @@ locking rules:
 		BKL	mmap_sem	PageLocked(page)
 open:		no	yes
 close:		no	yes
-fault:		no	yes
-page_mkwrite:	no	yes		no
+fault:		no	yes		can return with page locked
+page_mkwrite:	no	yes		can return with page locked
 access:		no	yes
 
-	->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.
+	->fault() is called when a previously not present pte is about
+to be faulted in. The filesystem must find and return the page associated
+with the passed in "pgoff" in the vm_fault structure. If it is possible that
+the page may be truncated and/or invalidated, then the filesystem must lock
+the page, then ensure it is not already truncated (the page lock will block
+subsequent truncate), and then return with VM_FAULT_LOCKED, and the page
+locked. The VM will unlock the page.
+
+	->page_mkwrite() is called when a previously read-only pte is
+about to become writeable. The filesystem again must ensure that there are
+no truncate/invalidate races, and then return with the page locked. If
+the page has been truncated, the filesystem should not look up a new page
+like the ->fault() handler, but simply return with VM_FAULT_NOPAGE, which
+will cause the VM to retry the fault.
 
 	->access() is called when get_user_pages() fails in
 acces_process_vm(), typically used to debug a process through