[PATCH 18/29] Unionfs: address-space operations
Includes writepage, writepages, readpage, prepare_write, and commit_write.
Signed-off-by: Erez Zadok <[EMAIL PROTECTED]>
---
fs/unionfs/mmap.c | 343 +
1 files changed, 343 insertions(+), 0 deletions(-)
create mode 100644 fs/unionfs/mmap.c
diff --git a/fs/unionfs/mmap.c b/fs/unionfs/mmap.c
new file mode 100644
index 000..ad770ac
--- /dev/null
+++ b/fs/unionfs/mmap.c
@@ -0,0 +1,343 @@
+/*
+ * Copyright (c) 2003-2007 Erez Zadok
+ * Copyright (c) 2003-2006 Charles P. Wright
+ * Copyright (c) 2005-2007 Josef 'Jeff' Sipek
+ * Copyright (c) 2005-2006 Junjiro Okajima
+ * Copyright (c) 2006 Shaya Potter
+ * Copyright (c) 2005 Arun M. Krishnakumar
+ * Copyright (c) 2004-2006 David P. Quigley
+ * Copyright (c) 2003-2004 Mohammad Nayyer Zubair
+ * Copyright (c) 2003 Puja Gupta
+ * Copyright (c) 2003 Harikesavan Krishnan
+ * Copyright (c) 2003-2007 Stony Brook University
+ * Copyright (c) 2003-2007 The Research Foundation of SUNY
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include "union.h"
+
+static int unionfs_writepage(struct page *page, struct writeback_control *wbc)
+{
+ int err = -EIO;
+ struct inode *inode;
+ struct inode *lower_inode;
+ struct page *lower_page;
+ struct address_space *lower_mapping; /* lower inode mapping */
+ gfp_t mask;
+
+ BUG_ON(!PageUptodate(page));
+ inode = page->mapping->host;
+ /* if no lower inode, nothing to do */
+ if (!inode || !UNIONFS_I(inode) || UNIONFS_I(inode)->lower_inodes) {
+ err = 0;
+ goto out;
+ }
+ lower_inode = unionfs_lower_inode(inode);
+ lower_mapping = lower_inode->i_mapping;
+
+ /*
+* find lower page (returns a locked page)
+*
+* We turn off __GFP_FS while we look for or create a new lower
+* page. This prevents a recursion into the file system code, which
+* under memory pressure conditions could lead to a deadlock. This
+* is similar to how the loop driver behaves (see loop_set_fd in
+* drivers/block/loop.c). If we can't find the lower page, we
+* redirty our page and return "success" so that the VM will call us
+* again in the (hopefully near) future.
+*/
+ mask = mapping_gfp_mask(lower_mapping) & ~(__GFP_FS);
+ lower_page = find_or_create_page(lower_mapping, page->index, mask);
+ if (!lower_page) {
+ err = 0;
+ set_page_dirty(page);
+ goto out;
+ }
+
+ /* copy page data from our upper page to the lower page */
+ copy_highpage(lower_page, page);
+ flush_dcache_page(lower_page);
+ SetPageUptodate(lower_page);
+ set_page_dirty(lower_page);
+
+ /*
+* Call lower writepage (expects locked page). However, if we are
+* called with wbc->for_reclaim, then the VFS/VM just wants to
+* reclaim our page. Therefore, we don't need to call the lower
+* ->writepage: just copy our data to the lower page (already done
+* above), then mark the lower page dirty and unlock it, and return
+* success.
+*/
+ if (wbc->for_reclaim) {
+ unlock_page(lower_page);
+ goto out_release;
+ }
+
+ BUG_ON(!lower_mapping->a_ops->writepage);
+ wait_on_page_writeback(lower_page); /* prevent multiple writers */
+ clear_page_dirty_for_io(lower_page); /* emulate VFS behavior */
+ err = lower_mapping->a_ops->writepage(lower_page, wbc);
+ if (err < 0)
+ goto out_release;
+
+ /*
+* Lower file systems such as ramfs and tmpfs, may return
+* AOP_WRITEPAGE_ACTIVATE so that the VM won't try to (pointlessly)
+* write the page again for a while. But those lower file systems
+* also set the page dirty bit back again. Since we successfully
+* copied our page data to the lower page, then the VM will come
+* back to the lower page (directly) and try to flush it. So we can
+* save the VM the hassle of coming back to our page and trying to
+* flush too. Therefore, we don't re-dirty our own page, and we
+* never return AOP_WRITEPAGE_ACTIVATE back to the VM (we consider
+* this a success).
+*
+* We also unlock the lower page if the lower ->writepage returned
+* AOP_WRITEPAGE_ACTIVATE. (This "anomalous" behaviour may be
+* addressed in future shmem/VM code.)
+*/
+ if (err == AOP_WRITEPAGE_ACTIVATE) {
+ err = 0;
+ unlock_page(lower_page);
+ }
+
+ /* all is well */
+
+ /* lower mtimes have changed: update ours */
+ unionfs_copy_attr_times(inode);
+
+out_release:
+
[PATCH 18/29] Unionfs: address-space operations
Includes writepage, writepages, readpage, prepare_write, and commit_write.
Signed-off-by: Erez Zadok [EMAIL PROTECTED]
---
fs/unionfs/mmap.c | 343 +
1 files changed, 343 insertions(+), 0 deletions(-)
create mode 100644 fs/unionfs/mmap.c
diff --git a/fs/unionfs/mmap.c b/fs/unionfs/mmap.c
new file mode 100644
index 000..ad770ac
--- /dev/null
+++ b/fs/unionfs/mmap.c
@@ -0,0 +1,343 @@
+/*
+ * Copyright (c) 2003-2007 Erez Zadok
+ * Copyright (c) 2003-2006 Charles P. Wright
+ * Copyright (c) 2005-2007 Josef 'Jeff' Sipek
+ * Copyright (c) 2005-2006 Junjiro Okajima
+ * Copyright (c) 2006 Shaya Potter
+ * Copyright (c) 2005 Arun M. Krishnakumar
+ * Copyright (c) 2004-2006 David P. Quigley
+ * Copyright (c) 2003-2004 Mohammad Nayyer Zubair
+ * Copyright (c) 2003 Puja Gupta
+ * Copyright (c) 2003 Harikesavan Krishnan
+ * Copyright (c) 2003-2007 Stony Brook University
+ * Copyright (c) 2003-2007 The Research Foundation of SUNY
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include union.h
+
+static int unionfs_writepage(struct page *page, struct writeback_control *wbc)
+{
+ int err = -EIO;
+ struct inode *inode;
+ struct inode *lower_inode;
+ struct page *lower_page;
+ struct address_space *lower_mapping; /* lower inode mapping */
+ gfp_t mask;
+
+ BUG_ON(!PageUptodate(page));
+ inode = page-mapping-host;
+ /* if no lower inode, nothing to do */
+ if (!inode || !UNIONFS_I(inode) || UNIONFS_I(inode)-lower_inodes) {
+ err = 0;
+ goto out;
+ }
+ lower_inode = unionfs_lower_inode(inode);
+ lower_mapping = lower_inode-i_mapping;
+
+ /*
+* find lower page (returns a locked page)
+*
+* We turn off __GFP_FS while we look for or create a new lower
+* page. This prevents a recursion into the file system code, which
+* under memory pressure conditions could lead to a deadlock. This
+* is similar to how the loop driver behaves (see loop_set_fd in
+* drivers/block/loop.c). If we can't find the lower page, we
+* redirty our page and return success so that the VM will call us
+* again in the (hopefully near) future.
+*/
+ mask = mapping_gfp_mask(lower_mapping) ~(__GFP_FS);
+ lower_page = find_or_create_page(lower_mapping, page-index, mask);
+ if (!lower_page) {
+ err = 0;
+ set_page_dirty(page);
+ goto out;
+ }
+
+ /* copy page data from our upper page to the lower page */
+ copy_highpage(lower_page, page);
+ flush_dcache_page(lower_page);
+ SetPageUptodate(lower_page);
+ set_page_dirty(lower_page);
+
+ /*
+* Call lower writepage (expects locked page). However, if we are
+* called with wbc-for_reclaim, then the VFS/VM just wants to
+* reclaim our page. Therefore, we don't need to call the lower
+* -writepage: just copy our data to the lower page (already done
+* above), then mark the lower page dirty and unlock it, and return
+* success.
+*/
+ if (wbc-for_reclaim) {
+ unlock_page(lower_page);
+ goto out_release;
+ }
+
+ BUG_ON(!lower_mapping-a_ops-writepage);
+ wait_on_page_writeback(lower_page); /* prevent multiple writers */
+ clear_page_dirty_for_io(lower_page); /* emulate VFS behavior */
+ err = lower_mapping-a_ops-writepage(lower_page, wbc);
+ if (err 0)
+ goto out_release;
+
+ /*
+* Lower file systems such as ramfs and tmpfs, may return
+* AOP_WRITEPAGE_ACTIVATE so that the VM won't try to (pointlessly)
+* write the page again for a while. But those lower file systems
+* also set the page dirty bit back again. Since we successfully
+* copied our page data to the lower page, then the VM will come
+* back to the lower page (directly) and try to flush it. So we can
+* save the VM the hassle of coming back to our page and trying to
+* flush too. Therefore, we don't re-dirty our own page, and we
+* never return AOP_WRITEPAGE_ACTIVATE back to the VM (we consider
+* this a success).
+*
+* We also unlock the lower page if the lower -writepage returned
+* AOP_WRITEPAGE_ACTIVATE. (This anomalous behaviour may be
+* addressed in future shmem/VM code.)
+*/
+ if (err == AOP_WRITEPAGE_ACTIVATE) {
+ err = 0;
+ unlock_page(lower_page);
+ }
+
+ /* all is well */
+
+ /* lower mtimes have changed: update ours */
+ unionfs_copy_attr_times(inode);
+
+out_release:
+ /* b/c
