Tao Ma
2010-Jul-12 07:19 UTC
[Ocfs2-devel] [PATCH] ocfs2: Don't duplicate page passes i_size during CoW.
During CoW, actually all the pages after i_size contains
garbage data, so don't read and duplicate them.
Signed-off-by: Tao Ma <tao.ma at oracle.com>
---
fs/ocfs2/refcounttree.c | 10 +++++++++-
1 files changed, 9 insertions(+), 1 deletions(-)
diff --git a/fs/ocfs2/refcounttree.c b/fs/ocfs2/refcounttree.c
index 1cf9cda..e082623 100644
--- a/fs/ocfs2/refcounttree.c
+++ b/fs/ocfs2/refcounttree.c
@@ -2921,7 +2921,7 @@ static int ocfs2_duplicate_clusters_by_page(handle_t
*handle,
struct super_block *sb = ocfs2_metadata_cache_get_super(ci);
u64 new_block = ocfs2_clusters_to_blocks(sb, new_cluster);
struct page *page;
- pgoff_t page_index;
+ pgoff_t page_index, last_page;
unsigned int from, to;
loff_t offset, end, map_end;
struct address_space *mapping = context->inode->i_mapping;
@@ -2932,12 +2932,20 @@ static int ocfs2_duplicate_clusters_by_page(handle_t
*handle,
offset = ((loff_t)cpos) << OCFS2_SB(sb)->s_clustersize_bits;
end = offset + (new_len << OCFS2_SB(sb)->s_clustersize_bits);
+ last_page = i_size_read(context->inode) >> PAGE_CACHE_SHIFT;
while (offset < end) {
page_index = offset >> PAGE_CACHE_SHIFT;
map_end = ((loff_t)page_index + 1) << PAGE_CACHE_SHIFT;
if (map_end > end)
map_end = end;
+ /*
+ * If this page is beyond the page contains i_size,
+ * stop duplicating it.
+ */
+ if (page_index > last_page)
+ break;
+
/* from, to is the offset within the page. */
from = offset & (PAGE_CACHE_SIZE - 1);
to = PAGE_CACHE_SIZE;
--
1.7.1.571.gba4d01
Joel Becker
2010-Jul-12 09:14 UTC
[Ocfs2-devel] [PATCH] ocfs2: Don't duplicate page passes i_size during CoW.
On Mon, Jul 12, 2010 at 03:19:48PM +0800, Tao Ma wrote:> During CoW, actually all the pages after i_size contains > garbage data, so don't read and duplicate them. > > Signed-off-by: Tao Ma <tao.ma at oracle.com> > --- > fs/ocfs2/refcounttree.c | 10 +++++++++- > 1 files changed, 9 insertions(+), 1 deletions(-) > > diff --git a/fs/ocfs2/refcounttree.c b/fs/ocfs2/refcounttree.c > index 1cf9cda..e082623 100644 > --- a/fs/ocfs2/refcounttree.c > +++ b/fs/ocfs2/refcounttree.c > @@ -2921,7 +2921,7 @@ static int ocfs2_duplicate_clusters_by_page(handle_t *handle, > struct super_block *sb = ocfs2_metadata_cache_get_super(ci); > u64 new_block = ocfs2_clusters_to_blocks(sb, new_cluster); > struct page *page; > - pgoff_t page_index; > + pgoff_t page_index, last_page; > unsigned int from, to; > loff_t offset, end, map_end; > struct address_space *mapping = context->inode->i_mapping; > @@ -2932,12 +2932,20 @@ static int ocfs2_duplicate_clusters_by_page(handle_t *handle, > offset = ((loff_t)cpos) << OCFS2_SB(sb)->s_clustersize_bits; > end = offset + (new_len << OCFS2_SB(sb)->s_clustersize_bits); > > + last_page = i_size_read(context->inode) >> PAGE_CACHE_SHIFT; > while (offset < end) {Why trigger on both index and byte offset? Why not just adjust end? if (end < i_size_read(context->inode)) end = i_size_read(inode); Then you don't need the last_page variable at all, because you're guaranteed never to go past i_size. Joel -- "Three o'clock is always too late or too early for anything you want to do." - Jean-Paul Sartre Joel Becker Consulting Software Developer Oracle E-mail: joel.becker at oracle.com Phone: (650) 506-8127