On Tue, Oct 07, 2008 at 05:05:54AM -0400, Christoph Hellwig wrote:
On Tue, Oct 07, 2008 at 02:15:31PM +0530, Aneesh Kumar K.V wrote:
+static int ext4_write_cache_pages(struct address_space *mapping,Looking at this functions the only difference is killing the
+ struct writeback_control *wbc, writepage_t writepage,
+ void *data)
+{
writeback_index and range_start updates. If they are bad why would we
only remove them from ext4?
I am also not updating wbc->nr_to_write.
ext4 delayed allocation writeback is bit tricky. It does
a) Look at the dirty pages and build an in memory extent of contiguous
logical file blocks. If we use writecache_pages to do that it will
update nr_to_write, writeback_index etc during this stage.
b) Request the block allocator for 'x' blocks. We get the value x from
step a.
c) block allocator may return less than 'x' contiguous block. That would
mean the variables updated by write_cache_pages need to corrected. The
old code was doing that. Chris Mason suggested it would make it easy
to use a write_cache_pages which doesn't update the variable for ext4.
I don't think other filesystem have this requirement.