From: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx> commit 2acf2c261b823d9d9ed954f348b97620297a36b5 upstream. With delayed allocation we lock the page in write_cache_pages() and try to build an in memory extent of contiguous blocks. This is needed so that we can get large contiguous blocks request. If range_cyclic mode is enabled, write_cache_pages() will loop back to the 0 index if no I/O has been done yet, and try to start writing from the beginning of the range. That causes an attempt to take the page lock of lower index page while holding the page lock of higher index page, which can cause a dead lock with another writeback thread. The solution is to implement the range_cyclic behavior in ext4_da_writepages() instead. http://bugzilla.kernel.org/show_bug.cgi?id=12579 Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx> Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx> Signed-off-by: Jayson R. King <dev@xxxxxxxxxxxxxx> Signed-off-by: Theodore Ts'o <tytso@xxxxxxx> --- fs/ext4/inode.c | 21 +++++++++++++++++++-- 1 files changed, 19 insertions(+), 2 deletions(-) diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 658ddef..0e4286a 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -2456,6 +2456,7 @@ static int ext4_da_writepages(struct address_space *mapping, struct inode *inode = mapping->host; int no_nrwrite_index_update; long pages_written = 0, pages_skipped; + int range_cyclic, cycled = 1, io_done = 0; int needed_blocks, ret = 0, nr_to_writebump = 0; struct ext4_sb_info *sbi = EXT4_SB(mapping->host->i_sb); @@ -2493,9 +2494,15 @@ static int ext4_da_writepages(struct address_space *mapping, if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) range_whole = 1; - if (wbc->range_cyclic) + range_cyclic = wbc->range_cyclic; + if (wbc->range_cyclic) { index = mapping->writeback_index; - else + if (index) + cycled = 0; + wbc->range_start = index << PAGE_CACHE_SHIFT; + wbc->range_end = LLONG_MAX; + wbc->range_cyclic = 0; + } else index = wbc->range_start >> PAGE_CACHE_SHIFT; mpd.wbc = wbc; @@ -2509,6 +2516,7 @@ static int ext4_da_writepages(struct address_space *mapping, wbc->no_nrwrite_index_update = 1; pages_skipped = wbc->pages_skipped; +retry: while (!ret && wbc->nr_to_write > 0) { /* @@ -2563,6 +2571,7 @@ static int ext4_da_writepages(struct address_space *mapping, pages_written += mpd.pages_written; wbc->pages_skipped = pages_skipped; ret = 0; + io_done = 1; } else if (wbc->nr_to_write) /* * There is no more writeout needed @@ -2571,6 +2580,13 @@ static int ext4_da_writepages(struct address_space *mapping, */ break; } + if (!io_done && !cycled) { + cycled = 1; + index = 0; + wbc->range_start = index << PAGE_CACHE_SHIFT; + wbc->range_end = mapping->writeback_index - 1; + goto retry; + } if (pages_skipped != wbc->pages_skipped) printk(KERN_EMERG "This should not happen leaving %s " "with nr_to_write = %ld ret = %d\n", @@ -2578,6 +2594,7 @@ static int ext4_da_writepages(struct address_space *mapping, /* Update index */ index += pages_written; + wbc->range_cyclic = range_cyclic; if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0)) /* * set the writeback_index so that range_cyclic -- 1.6.6.1.1.g974db.dirty -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
