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;
--
1.7.3.1
--
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