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f2fs: fix to avoid potential deadlock
[ Upstream commit344150999b
] Quoted from Jing Xia's report, there is a potential deadlock may happen between kworker and checkpoint as below: [T:writeback] [T:checkpoint] - wb_writeback - blk_start_plug bio contains NodeA was plugged in writeback threads - do_writepages -- sync write inodeB, inc wb_sync_req[DATA] - f2fs_write_data_pages - f2fs_write_single_data_page -- write last dirty page - f2fs_do_write_data_page - set_page_writeback -- clear page dirty flag and PAGECACHE_TAG_DIRTY tag in radix tree - f2fs_outplace_write_data - f2fs_update_data_blkaddr - f2fs_wait_on_page_writeback -- wait NodeA to writeback here - inode_dec_dirty_pages - writeback_sb_inodes - writeback_single_inode - do_writepages - f2fs_write_data_pages -- skip writepages due to wb_sync_req[DATA] - wbc->pages_skipped += get_dirty_pages() -- PAGECACHE_TAG_DIRTY is not set but get_dirty_pages() returns one - requeue_inode -- requeue inode to wb->b_dirty queue due to non-zero.pages_skipped - blk_finish_plug Let's try to avoid deadlock condition by forcing unplugging previous bio via blk_finish_plug(current->plug) once we'v skipped writeback in writepages() due to valid sbi->wb_sync_req[DATA/NODE]. Fixes:687de7f101
("f2fs: avoid IO split due to mixed WB_SYNC_ALL and WB_SYNC_NONE") Signed-off-by: Zhiguo Niu <zhiguo.niu@unisoc.com> Signed-off-by: Jing Xia <jing.xia@unisoc.com> Signed-off-by: Chao Yu <chao@kernel.org> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
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parent
feedbfeb22
commit
06f6c6fc83
2 changed files with 10 additions and 2 deletions
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@ -3163,8 +3163,12 @@ static int __f2fs_write_data_pages(struct address_space *mapping,
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/* to avoid spliting IOs due to mixed WB_SYNC_ALL and WB_SYNC_NONE */
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if (wbc->sync_mode == WB_SYNC_ALL)
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atomic_inc(&sbi->wb_sync_req[DATA]);
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else if (atomic_read(&sbi->wb_sync_req[DATA]))
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else if (atomic_read(&sbi->wb_sync_req[DATA])) {
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/* to avoid potential deadlock */
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if (current->plug)
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blk_finish_plug(current->plug);
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goto skip_write;
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}
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if (__should_serialize_io(inode, wbc)) {
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mutex_lock(&sbi->writepages);
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@ -2111,8 +2111,12 @@ static int f2fs_write_node_pages(struct address_space *mapping,
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if (wbc->sync_mode == WB_SYNC_ALL)
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atomic_inc(&sbi->wb_sync_req[NODE]);
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else if (atomic_read(&sbi->wb_sync_req[NODE]))
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else if (atomic_read(&sbi->wb_sync_req[NODE])) {
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/* to avoid potential deadlock */
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if (current->plug)
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blk_finish_plug(current->plug);
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goto skip_write;
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}
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trace_f2fs_writepages(mapping->host, wbc, NODE);
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