On 05/09, Chao Yu wrote: > On 2020/5/9 0:10, Jaegeuk Kim wrote: > > Hi Sayali, > > > > In order to address the perf regression, how about this? > > > >>From 48418af635884803ffb35972df7958a2e6649322 Mon Sep 17 00:00:00 2001 > > From: Jaegeuk Kim <[email protected]> > > Date: Fri, 8 May 2020 09:08:37 -0700 > > Subject: [PATCH] f2fs: avoid double lock for cp_rwsem during checkpoint > > > > There could be a scenario where f2fs_sync_node_pages gets > > called during checkpoint, which in turn tries to flush > > inline data and calls iput(). This results in deadlock as > > iput() tries to hold cp_rwsem, which is already held at the > > beginning by checkpoint->block_operations(). > > > > Call stack : > > > > Thread A Thread B > > f2fs_write_checkpoint() > > - block_operations(sbi) > > - f2fs_lock_all(sbi); > > - down_write(&sbi->cp_rwsem); > > > > - open() > > - igrab() > > - write() write inline data > > - unlink() > > - f2fs_sync_node_pages() > > - if (is_inline_node(page)) > > - flush_inline_data() > > - ilookup() > > page = f2fs_pagecache_get_page() > > if (!page) > > goto iput_out; > > iput_out: > > -close() > > -iput() > > iput(inode); > > - f2fs_evict_inode() > > - f2fs_truncate_blocks() > > - f2fs_lock_op() > > - down_read(&sbi->cp_rwsem); > > > > Fixes: 2049d4fcb057 ("f2fs: avoid multiple node page writes due to > > inline_data") > > Signed-off-by: Sayali Lokhande <[email protected]> > > Signed-off-by: Jaegeuk Kim <[email protected]> > > --- > > fs/f2fs/node.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c > > index 1db8cabf727ef..626d7daca09de 100644 > > --- a/fs/f2fs/node.c > > +++ b/fs/f2fs/node.c > > @@ -1870,8 +1870,8 @@ int f2fs_sync_node_pages(struct f2fs_sb_info *sbi, > > goto continue_unlock; > > } > > > > - /* flush inline_data */ > > - if (is_inline_node(page)) { > > + /* flush inline_data, if it's not sync path. */ > > + if (do_balance && is_inline_node(page)) { > > IIRC, this flow was designed to avoid running out of free space issue > during checkpoint: > > 2049d4fcb057 ("f2fs: avoid multiple node page writes due to inline_data") > > The sceanrio is: > 1. create fully node blocks > 2. flush node blocks > 3. write inline_data for all the node blocks again > 4. flush node blocks redundantly > > I guess this may cause failing one case of fstest.
Yeah, actually I was hitting 204 failure, and thus, revised like this. Now, I don't see any regression in fstest. >From 8f1882acfb0a5fc43e5a2bbd576a8f3c681a7d2c Mon Sep 17 00:00:00 2001 From: Sayali Lokhande <[email protected]> Date: Thu, 30 Apr 2020 16:28:29 +0530 Subject: [PATCH] f2fs: Avoid double lock for cp_rwsem during checkpoint There could be a scenario where f2fs_sync_node_pages gets called during checkpoint, which in turn tries to flush inline data and calls iput(). This results in deadlock as iput() tries to hold cp_rwsem, which is already held at the beginning by checkpoint->block_operations(). Call stack : Thread A Thread B f2fs_write_checkpoint() - block_operations(sbi) - f2fs_lock_all(sbi); - down_write(&sbi->cp_rwsem); - open() - igrab() - write() write inline data - unlink() - f2fs_sync_node_pages() - if (is_inline_node(page)) - flush_inline_data() - ilookup() page = f2fs_pagecache_get_page() if (!page) goto iput_out; iput_out: -close() -iput() iput(inode); - f2fs_evict_inode() - f2fs_truncate_blocks() - f2fs_lock_op() - down_read(&sbi->cp_rwsem); Fixes: 2049d4fcb057 ("f2fs: avoid multiple node page writes due to inline_data") Signed-off-by: Sayali Lokhande <[email protected]> Signed-off-by: Jaegeuk Kim <[email protected]> --- fs/f2fs/checkpoint.c | 9 ++++++++- fs/f2fs/f2fs.h | 4 ++-- fs/f2fs/node.c | 10 +++++----- 3 files changed, 15 insertions(+), 8 deletions(-) diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c index d49f7a01d8a26..928aea4ff663d 100644 --- a/fs/f2fs/checkpoint.c +++ b/fs/f2fs/checkpoint.c @@ -1168,6 +1168,12 @@ static int block_operations(struct f2fs_sb_info *sbi) }; int err = 0, cnt = 0; + /* + * Let's flush node pages first to flush inline_data. + * We'll actually guarantee everything below under f2fs_lock_all. + */ + f2fs_sync_node_pages(sbi, &wbc, false, false, FS_CP_NODE_IO); + retry_flush_quotas: f2fs_lock_all(sbi); if (__need_flush_quota(sbi)) { @@ -1222,7 +1228,8 @@ static int block_operations(struct f2fs_sb_info *sbi) if (get_pages(sbi, F2FS_DIRTY_NODES)) { up_write(&sbi->node_write); atomic_inc(&sbi->wb_sync_req[NODE]); - err = f2fs_sync_node_pages(sbi, &wbc, false, FS_CP_NODE_IO); + err = f2fs_sync_node_pages(sbi, &wbc, false, + true, FS_CP_NODE_IO); atomic_dec(&sbi->wb_sync_req[NODE]); if (err) { up_write(&sbi->node_change); diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h index d916540f12813..ac6ae42b9dd4e 100644 --- a/fs/f2fs/f2fs.h +++ b/fs/f2fs/f2fs.h @@ -3286,8 +3286,8 @@ int f2fs_fsync_node_pages(struct f2fs_sb_info *sbi, struct inode *inode, struct writeback_control *wbc, bool atomic, unsigned int *seq_id); int f2fs_sync_node_pages(struct f2fs_sb_info *sbi, - struct writeback_control *wbc, - bool do_balance, enum iostat_type io_type); + struct writeback_control *wbc, + bool do_balance, bool sync, enum iostat_type io_type); int f2fs_build_free_nids(struct f2fs_sb_info *sbi, bool sync, bool mount); bool f2fs_alloc_nid(struct f2fs_sb_info *sbi, nid_t *nid); void f2fs_alloc_nid_done(struct f2fs_sb_info *sbi, nid_t nid); diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c index 1db8cabf727ef..fd00a8c119088 100644 --- a/fs/f2fs/node.c +++ b/fs/f2fs/node.c @@ -1808,8 +1808,8 @@ static bool flush_dirty_inode(struct page *page) } int f2fs_sync_node_pages(struct f2fs_sb_info *sbi, - struct writeback_control *wbc, - bool do_balance, enum iostat_type io_type) + struct writeback_control *wbc, + bool do_balance, bool sync, enum iostat_type io_type) { pgoff_t index; struct pagevec pvec; @@ -1870,8 +1870,8 @@ int f2fs_sync_node_pages(struct f2fs_sb_info *sbi, goto continue_unlock; } - /* flush inline_data */ - if (is_inline_node(page)) { + /* flush inline_data, if it's async context. */ + if (!sync && is_inline_node(page)) { clear_inline_node(page); unlock_page(page); flush_inline_data(sbi, ino_of_node(page)); @@ -1999,7 +1999,7 @@ static int f2fs_write_node_pages(struct address_space *mapping, diff = nr_pages_to_write(sbi, NODE, wbc); blk_start_plug(&plug); - f2fs_sync_node_pages(sbi, wbc, true, FS_NODE_IO); + f2fs_sync_node_pages(sbi, wbc, true, false, FS_NODE_IO); blk_finish_plug(&plug); wbc->nr_to_write = max((long)0, wbc->nr_to_write - diff); -- 2.26.2.645.ge9eca65c58-goog
