Re: [PATCH 3/6] writeback: make nr_to_write a per-file limit
From: Christoph Hellwig
Date: Wed May 04 2011 - 05:42:34 EST
On Wed, May 04, 2011 at 05:17:10PM +0800, Wu Fengguang wrote:
> This ensures large dirty files can be written in the full 4MB writeback
> chunk size, rather than whatever remained quota in wbc->nr_to_write.
I like the high-level idea, but the implementation of overriding
nr_to_write and then copying it back seems rather ugly.
The basic problem seems to be that struct writeback_control is
designed to control writeback of a single file, but we keep abuse it
for writing multiple files in writeback_sb_inodes and its callers.
It seems like we should only build the struct writeback_control from
struct wb_writeback_work down in writeback_sb_inodes, even if that
means passing some more information to it either in struct
wb_writeback_work or on the stack.
Then writeback_sb_inodes can do something like
if (wbc.sync_mode == WB_SYNC_NONE)
wbc.nr_to_write = min(MAX_WRITEBACK_PAGES, work->nr_pages);
else
wbc.nr_to_write = LONG_MAX;
for each inode it writes.
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