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authorNick Piggin <npiggin@suse.de>2007-07-19 01:46:59 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-07-19 10:04:41 -0700
commit54cb8821de07f2ffcd28c380ce9b93d5784b40d7 (patch)
tree1de676534963d96af42863b20191bc9f80060dea /Documentation
parentd00806b183152af6d24f46f0c33f14162ca1262a (diff)
mm: merge populate and nopage into fault (fixes nonlinear)
Nonlinear mappings are (AFAIKS) simply a virtual memory concept that encodes the virtual address -> file offset differently from linear mappings. ->populate is a layering violation because the filesystem/pagecache code should need to know anything about the virtual memory mapping. The hitch here is that the ->nopage handler didn't pass down enough information (ie. pgoff). But it is more logical to pass pgoff rather than have the ->nopage function calculate it itself anyway (because that's a similar layering violation). Having the populate handler install the pte itself is likewise a nasty thing to be doing. This patch introduces a new fault handler that replaces ->nopage and ->populate and (later) ->nopfn. Most of the old mechanism is still in place so there is a lot of duplication and nice cleanups that can be removed if everyone switches over. The rationale for doing this in the first place is that nonlinear mappings are subject to the pagefault vs invalidate/truncate race too, and it seemed stupid to duplicate the synchronisation logic rather than just consolidate the two. After this patch, MAP_NONBLOCK no longer sets up ptes for pages present in pagecache. Seems like a fringe functionality anyway. NOPAGE_REFAULT is removed. This should be implemented with ->fault, and no users have hit mainline yet. [akpm@linux-foundation.org: cleanup] [randy.dunlap@oracle.com: doc. fixes for readahead] [akpm@linux-foundation.org: build fix] Signed-off-by: Nick Piggin <npiggin@suse.de> Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com> Cc: Mark Fasheh <mark.fasheh@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/feature-removal-schedule.txt27
-rw-r--r--Documentation/filesystems/Locking2
2 files changed, 29 insertions, 0 deletions
diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt
index 66c8b4b165c..716568afdff 100644
--- a/Documentation/feature-removal-schedule.txt
+++ b/Documentation/feature-removal-schedule.txt
@@ -135,6 +135,33 @@ Who: Greg Kroah-Hartman <gregkh@suse.de>
---------------------------
+What: filemap_nopage, filemap_populate
+When: April 2007
+Why: These legacy interfaces no longer have any callers in the kernel and
+ any functionality provided can be provided with filemap_fault. The
+ removal schedule is short because they are a big maintainence burden
+ and have some bugs.
+Who: Nick Piggin <npiggin@suse.de>
+
+---------------------------
+
+What: vm_ops.populate, install_page
+When: April 2007
+Why: These legacy interfaces no longer have any callers in the kernel and
+ any functionality provided can be provided with vm_ops.fault.
+Who: Nick Piggin <npiggin@suse.de>
+
+---------------------------
+
+What: vm_ops.nopage
+When: February 2008, provided in-kernel callers have been converted
+Why: This interface is replaced by vm_ops.fault, but it has been around
+ forever, is used by a lot of drivers, and doesn't cost much to
+ maintain.
+Who: Nick Piggin <npiggin@suse.de>
+
+---------------------------
+
What: Interrupt only SA_* flags
When: September 2007
Why: The interrupt related SA_* flags are replaced by IRQF_* to move them
diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
index d866551be03..970c8ec1a05 100644
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -510,12 +510,14 @@ More details about quota locking can be found in fs/dquot.c.
prototypes:
void (*open)(struct vm_area_struct*);
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 *);
locking rules:
BKL mmap_sem
open: no yes
close: no yes
+fault: no yes
nopage: no yes
================================================================================