Messages in this thread Patch in this message | | | From | niuzhiguo84@gmail ... | Subject | [PATCH Vx 1/1] f2fs: Avoid deadlock between writeback and checkpoint | Date | Tue, 9 Nov 2021 14:16:48 +0800 |
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From: Zhiguo Niu <zhiguo.niu@unisoc.com>
There could be a scenario as following: The inodeA and inodeB are in b_io queue of writeback inodeA : f2fs's node inode inodeB : a dir inode with only one dirty pages, and the node page of inodeB cached into inodeA
writeback:
wb_workfn wb_writeback blk_start_plug loop { queue_io progress=__writeback_inodes_wb __writeback_single_inode do_writepages f2fs_write_data_pages wbc->pages_skipped +=get_dirty_pages inode->i_state &= ~dirty wrote++ requeue_inode } blk_finish_plug
checkpoint:
f2fs_write_checkpoint f2fs_sync_dirty_inodes filemap_fdatawrite do_writepages f2fs_write_data_pages f2fs_write_single_data_page f2fs_do_write_data_page set_page_writeback f2fs_outplace_write_data f2fs_update_data_blkaddr f2fs_wait_on_page_writeback inode_dec_dirty_pages
1. Writeback thread flush inodeA, and push it's bio request in task's plug; 2. Checkpoint thread writes inodeB's dirty page, and then wait its node page writeback cached into inodeA which is in writeback task's plug 3. Writeback thread flush inodeB and skip writing the dirty page as wb_sync_req[DATA] > 0. 4. As none of the inodeB's page is marked as PAGECACHE_TAG_DIRTY, writeback thread clear inodeB's dirty state. 5. Then inodeB is moved from b_io to b_dirty because of pages_skipped > 0 as checkpoint thread is stuck before dec dirty_pages.
This patch collect correct pages_skipped according to the tag state in page tree of inode
Signed-off-by: Zhiguo Niu <zhiguo.niu@unisoc.com> Signed-off-by: Jing Xia <jing.xia@unisoc.com> --- fs/f2fs/data.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c index f4fd6c246c9a..e98628e3868c 100644 --- a/fs/f2fs/data.c +++ b/fs/f2fs/data.c @@ -3237,7 +3237,9 @@ static int __f2fs_write_data_pages(struct address_space *mapping, return ret; skip_write: - wbc->pages_skipped += get_dirty_pages(inode); + wbc->pages_skipped += + mapping_tagged(inode->i_mapping, PAGECACHE_TAG_DIRTY) ? + get_dirty_pages(inode) : 0; trace_f2fs_writepages(mapping->host, wbc, DATA); return 0; } -- 2.28.0
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