Messages in this thread | | | Subject | Re: [PATCH V4] f2fs: Avoid double lock for cp_rwsem during checkpoint | From | Chao Yu <> | Date | Tue, 12 May 2020 09:57:59 +0800 |
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On 2020/5/12 6:11, Jaegeuk Kim wrote: > On 05/11, Chao Yu wrote: >> On 2020/5/10 3:03, Jaegeuk Kim wrote: >>> 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 <jaegeuk@kernel.org> >>>>> 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 <sayalil@codeaurora.org> >>>>> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org> >>>>> --- >>>>> 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 <sayalil@codeaurora.org> >>> 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 <sayalil@codeaurora.org> >>> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org> >>> --- >>> 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); >> >> It is possible that user write a large number of inline data in between >> f2fs_sync_node_pages() and f2fs_lock_all(), it will cause the no-space issue in >> race condition. >> >> Also, if there is huge number of F2FS_DIRTY_IMETA, after this change, we will >> flush inode page twice which is unneeded. >> >> f2fs_sync_node_pages() --- flush dirty inode page >> f2fs_lock_all() >> ... >> f2fs_sync_inode_meta() --- update dirty inode page >> f2fs_sync_node_pages() --- flush dirty inode page again. >> > > Another version: > >>From 6b430b72af57c65c20dea7b87f7ba7e9df36be98 Mon Sep 17 00:00:00 2001 > From: Sayali Lokhande <sayalil@codeaurora.org> > 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 <sayalil@codeaurora.org> > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org> > --- > fs/f2fs/checkpoint.c | 5 +++++ > fs/f2fs/f2fs.h | 1 + > fs/f2fs/node.c | 51 ++++++++++++++++++++++++++++++++++++++++++-- > 3 files changed, 55 insertions(+), 2 deletions(-) > > diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c > index d49f7a01d8a26..79e605f38f4fa 100644 > --- a/fs/f2fs/checkpoint.c > +++ b/fs/f2fs/checkpoint.c > @@ -1168,6 +1168,11 @@ static int block_operations(struct f2fs_sb_info *sbi) > }; > int err = 0, cnt = 0; > > + /* > + * Let's flush inline_data in dirty node pages. > + */ > + f2fs_flush_inline_data(sbi);
Still there is a gap, user can write a large number of inline data here...
Would that be enough? I doubt we can suffer this issue in below pathes as well:
- block_operations - f2fs_sync_dirty_inodes - iput - f2fs_sync_inode_meta - iput
Thanks,
> + > retry_flush_quotas: > f2fs_lock_all(sbi); > if (__need_flush_quota(sbi)) { > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h > index 2a8ea81c52a15..7f3d259e7e376 100644 > --- a/fs/f2fs/f2fs.h > +++ b/fs/f2fs/f2fs.h > @@ -3282,6 +3282,7 @@ void f2fs_ra_node_page(struct f2fs_sb_info *sbi, nid_t nid); > struct page *f2fs_get_node_page(struct f2fs_sb_info *sbi, pgoff_t nid); > struct page *f2fs_get_node_page_ra(struct page *parent, int start); > int f2fs_move_node_page(struct page *node_page, int gc_type); > +int f2fs_flush_inline_data(struct f2fs_sb_info *sbi); > int f2fs_fsync_node_pages(struct f2fs_sb_info *sbi, struct inode *inode, > struct writeback_control *wbc, bool atomic, > unsigned int *seq_id); > diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c > index 1db8cabf727ef..e632de10aedab 100644 > --- a/fs/f2fs/node.c > +++ b/fs/f2fs/node.c > @@ -1807,6 +1807,53 @@ static bool flush_dirty_inode(struct page *page) > return true; > } > > +int f2fs_flush_inline_data(struct f2fs_sb_info *sbi) > +{ > + pgoff_t index = 0; > + struct pagevec pvec; > + int nr_pages; > + int ret = 0; > + > + pagevec_init(&pvec); > + > + while ((nr_pages = pagevec_lookup_tag(&pvec, > + NODE_MAPPING(sbi), &index, PAGECACHE_TAG_DIRTY))) { > + int i; > + > + for (i = 0; i < nr_pages; i++) { > + struct page *page = pvec.pages[i]; > + > + if (!IS_DNODE(page)) > + continue; > + > + lock_page(page); > + > + if (unlikely(page->mapping != NODE_MAPPING(sbi))) { > +continue_unlock: > + unlock_page(page); > + continue; > + } > + > + if (!PageDirty(page)) { > + /* someone wrote it for us */ > + goto continue_unlock; > + } > + > + /* flush inline_data, if it's async context. */ > + if (is_inline_node(page)) { > + clear_inline_node(page); > + unlock_page(page); > + flush_inline_data(sbi, ino_of_node(page)); > + continue; > + } > + unlock_page(page); > + } > + pagevec_release(&pvec); > + cond_resched(); > + } > + return ret; > +} > + > int f2fs_sync_node_pages(struct f2fs_sb_info *sbi, > struct writeback_control *wbc, > bool do_balance, enum iostat_type io_type) > @@ -1870,8 +1917,8 @@ 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 (do_balance && is_inline_node(page)) { > clear_inline_node(page); > unlock_page(page); > flush_inline_data(sbi, ino_of_node(page)); >
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