On Sat, Feb 12, 2011 at 07:15:54PM -0500, Theodore Ts'o wrote:
> Because the ext4 page writeback codepath had been prematurely calling
> clear_page_dirty_for_io(), if it turned out that a particular page
> couldn't be written out during a particular pass of
> write_cache_pages_da(), the page would have to get redirtied by
> calling redirty_pages_for_writeback(). Not only was this wasted work,
> but redirty_page_for_writeback() would increment wbc->pages_skipped to
> signal to writeback_sb_inodes() that buffers were locked, and that it
> should skip this inode until later.
>
> Since this signal was incorrect in ext4's case --- which was caused by
> ext4's historically incorrect use of write_cache_pages() ---
> ext4_da_writepages() saved and restored wbc->skipped_pages to avoid
> confusing writeback_sb_inodes().
>
> Now that we've fixed ext4 to call clear_page_dirty_for_io() right
> before initiating the page I/O, we can nuke the page_skipped
> save/restore hackery, and breathe a sigh of relief.
>
> Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
> ---
> fs/ext4/inode.c | 10 ----------
> 1 files changed, 0 insertions(+), 10 deletions(-)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 3eca465..6dfdc0e 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -2900,7 +2900,6 @@ static int ext4_da_writepages(struct address_space *mapping,
> struct mpage_da_data mpd;
> struct inode *inode = mapping->host;
> int pages_written = 0;
> - long pages_skipped;
> unsigned int max_pages;
> int range_cyclic, cycled = 1, io_done = 0;
> int needed_blocks, ret = 0;
> @@ -2986,8 +2985,6 @@ static int ext4_da_writepages(struct address_space *mapping,
> mpd.wbc = wbc;
> mpd.inode = mapping->host;
>
> - pages_skipped = wbc->pages_skipped;
> -
> retry:
> if (wbc->sync_mode == WB_SYNC_ALL)
> tag_pages_for_writeback(mapping, index, end);
> @@ -3047,7 +3044,6 @@ retry:
> * and try again
> */
> jbd2_journal_force_commit_nested(sbi->s_journal);
> - wbc->pages_skipped = pages_skipped;
> ret = 0;
> } else if (ret == MPAGE_DA_EXTENT_TAIL) {
> /*
> @@ -3055,7 +3051,6 @@ retry:
> * rest of the pages
> */
> pages_written += mpd.pages_written;
> - wbc->pages_skipped = pages_skipped;
> ret = 0;
> io_done = 1;
> } else if (wbc->nr_to_write)
> @@ -3073,11 +3068,6 @@ retry:
> wbc->range_end = mapping->writeback_index - 1;
> goto retry;
> }
> - if (pages_skipped != wbc->pages_skipped)
> - ext4_msg(inode->i_sb, KERN_CRIT,
> - "This should not happen leaving %s "
> - "with nr_to_write = %ld ret = %d",
> - __func__, wbc->nr_to_write, ret);
>
> /* Update index */
> wbc->range_cyclic = range_cyclic;
Looks good.
Josef
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