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Message-ID: <20140822154800.GA90003@jaegeuk-mac02.mot-mobility.com>
Date: Fri, 22 Aug 2014 08:49:31 -0700
From: Jaegeuk Kim <jaegeuk@...nel.org>
To: Chao Yu <chao2.yu@...sung.com>
Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH 3/4] f2fs: avoid double lock in truncate_blocks
On Fri, Aug 22, 2014 at 02:56:37PM +0800, Chao Yu wrote:
> Hi Jaegeuk,
>
> > -----Original Message-----
> > From: Jaegeuk Kim [mailto:jaegeuk@...nel.org]
> > Sent: Friday, August 22, 2014 12:45 AM
> > To: Chao Yu
> > Cc: linux-fsdevel@...r.kernel.org; linux-kernel@...r.kernel.org;
> > linux-f2fs-devel@...ts.sourceforge.net
> > Subject: Re: [f2fs-dev] [PATCH 3/4] f2fs: avoid double lock in truncate_blocks
> >
> > On Wed, Aug 20, 2014 at 10:07:04AM +0800, Chao Yu wrote:
> > > > -----Original Message-----
> > > > From: Jaegeuk Kim [mailto:jaegeuk@...nel.org]
> > > > Sent: Wednesday, August 20, 2014 12:58 AM
> > > > To: Chao Yu
> > > > Cc: linux-fsdevel@...r.kernel.org; linux-kernel@...r.kernel.org;
> > > > linux-f2fs-devel@...ts.sourceforge.net
> > > > Subject: Re: [f2fs-dev] [PATCH 3/4] f2fs: avoid double lock in truncate_blocks
> > > >
> > > > On Tue, Aug 19, 2014 at 04:04:11PM +0800, Chao Yu wrote:
> > > > > Hi Jaegeuk,
> > > > >
> > > > > > -----Original Message-----
> > > > > > From: Jaegeuk Kim [mailto:jaegeuk@...nel.org]
> > > > > > Sent: Saturday, August 16, 2014 6:04 AM
> > > > > > To: linux-kernel@...r.kernel.org; linux-fsdevel@...r.kernel.org;
> > > > > > linux-f2fs-devel@...ts.sourceforge.net
> > > > > > Cc: Jaegeuk Kim
> > > > > > Subject: [f2fs-dev] [PATCH 3/4] f2fs: avoid double lock in truncate_blocks
> > > > > >
> > > > > > The init_inode_metadata calls truncate_blocks when error is occurred.
> > > > > > The callers holds f2fs_lock_op, so we should not call it again in
> > > > > > truncate_blocks.
> > > > >
> > > > > Nice catch! Your solution is a good way to fix this issue.
> > > > >
> > > > > Previously, in create inode path, I found there are some redundant codes between
> > > > > init_inode_metadata and evict_inode, including:
> > > > > truncate_inode_pages(&inode->i_data, 0);
> > > > > truncate_blocks(inode, 0);
> > > > > remove_dirty_dir_inode(inode);
> > > > > remove_inode_page(inode);
> > > > >
> > > > > So I think there is another way to fix this issue by removing error path handling
> > > > > codes in init_inode_metadata, not making the inode bad to left garbage clean work in
> > > > > evict_inode. In this way we can avoid adding additional argument for all different
> > > > > callers.
> > > >
> > > > Well, possible.
> > > > But we need to take a closer look at the race condition on the inode cache.
> > > > What can happen if this bad inode is reassigned to the other thread?
> > >
> > > I don't get it. As I know, in evict(), we call ->evict_inode before
> > > remove_inode_hash(), so before all clean work was done we will not reassign
> > > this hashed uncleaned inode to other thread.
> > >
> > > Am I missing anything?
> >
> > What I meant was it may happen between init_inode_metadata and iput.
>
> Actually, can happen between unlock_new_inode and iput in error path of
> create/symlink/mkdir/mknod/tmpfile. Scenario is like this:
>
> ->f2fs_mkdir
> ->f2fs_add_link
> ->__f2fs_add_link
> ->init_inode_metadata failed here
> ->gc_thread_func
> ->f2fs_gc
> ->do_garbage_collect
> ->gc_data_segment
> ->f2fs_iget
> ->iget_locked
> ->wait_on_inode
> ->unlock_new_inode
> ->move_data_page
> ->make_bad_inode
> ->iput
>
> No problem now, but I'd like to remove unlock_new_inode from error path of inode
> creating procedure as we'd better wakeup waiter in end of ->iput instead of
> wakeup waiter in unlock_new_inode before invoking make_bad_inod.
>
> How do you think?
Hmm. It seems that this is a lot different issue wrt this patch.
Anyway, I agreed that it needs to relocate unlock_new_inode.
Thanks,
>
> Anyway, drop this proposal if you do not like it, although I think it will be
> ok theoretically after we fix above issue.
>
> Thanks,
> Yu
>
> >
> > Thanks,
> >
> > >
> > > Regards,
> > > Yu
> > >
> > > >
> > > > >
> > > > > How do you think?
> > > > >
> > > > > Thanks,
> > > > > Yu
> > > > >
> > > > > >
> > > > > > Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
> > > > > > ---
> > > > > > fs/f2fs/data.c | 2 +-
> > > > > > fs/f2fs/dir.c | 2 +-
> > > > > > fs/f2fs/f2fs.h | 2 +-
> > > > > > fs/f2fs/file.c | 13 ++++++++-----
> > > > > > fs/f2fs/inline.c | 2 +-
> > > > > > 5 files changed, 12 insertions(+), 9 deletions(-)
> > > > > >
> > > > > > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> > > > > > index 68834e2..14cc3e8 100644
> > > > > > --- a/fs/f2fs/data.c
> > > > > > +++ b/fs/f2fs/data.c
> > > > > > @@ -935,7 +935,7 @@ static void f2fs_write_failed(struct address_space *mapping, loff_t
> > > > to)
> > > > > >
> > > > > > if (to > inode->i_size) {
> > > > > > truncate_pagecache(inode, inode->i_size);
> > > > > > - truncate_blocks(inode, inode->i_size);
> > > > > > + truncate_blocks(inode, inode->i_size, true);
> > > > > > }
> > > > > > }
> > > > > >
> > > > > > diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
> > > > > > index a69bbfa..155fb05 100644
> > > > > > --- a/fs/f2fs/dir.c
> > > > > > +++ b/fs/f2fs/dir.c
> > > > > > @@ -391,7 +391,7 @@ put_error:
> > > > > > error:
> > > > > > /* once the failed inode becomes a bad inode, i_mode is S_IFREG */
> > > > > > truncate_inode_pages(&inode->i_data, 0);
> > > > > > - truncate_blocks(inode, 0);
> > > > > > + truncate_blocks(inode, 0, false);
> > > > > > remove_dirty_dir_inode(inode);
> > > > > > remove_inode_page(inode);
> > > > > > return ERR_PTR(err);
> > > > > > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > > > > > index 2723b2d..7f976c1 100644
> > > > > > --- a/fs/f2fs/f2fs.h
> > > > > > +++ b/fs/f2fs/f2fs.h
> > > > > > @@ -1122,7 +1122,7 @@ static inline void f2fs_stop_checkpoint(struct f2fs_sb_info *sbi)
> > > > > > */
> > > > > > int f2fs_sync_file(struct file *, loff_t, loff_t, int);
> > > > > > void truncate_data_blocks(struct dnode_of_data *);
> > > > > > -int truncate_blocks(struct inode *, u64);
> > > > > > +int truncate_blocks(struct inode *, u64, bool);
> > > > > > void f2fs_truncate(struct inode *);
> > > > > > int f2fs_getattr(struct vfsmount *, struct dentry *, struct kstat *);
> > > > > > int f2fs_setattr(struct dentry *, struct iattr *);
> > > > > > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> > > > > > index ecbdf6a..a8e97f8 100644
> > > > > > --- a/fs/f2fs/file.c
> > > > > > +++ b/fs/f2fs/file.c
> > > > > > @@ -422,7 +422,7 @@ out:
> > > > > > f2fs_put_page(page, 1);
> > > > > > }
> > > > > >
> > > > > > -int truncate_blocks(struct inode *inode, u64 from)
> > > > > > +int truncate_blocks(struct inode *inode, u64 from, bool lock)
> > > > > > {
> > > > > > struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
> > > > > > unsigned int blocksize = inode->i_sb->s_blocksize;
> > > > > > @@ -438,14 +438,16 @@ int truncate_blocks(struct inode *inode, u64 from)
> > > > > > free_from = (pgoff_t)
> > > > > > ((from + blocksize - 1) >> (sbi->log_blocksize));
> > > > > >
> > > > > > - f2fs_lock_op(sbi);
> > > > > > + if (lock)
> > > > > > + f2fs_lock_op(sbi);
> > > > > >
> > > > > > set_new_dnode(&dn, inode, NULL, NULL, 0);
> > > > > > err = get_dnode_of_data(&dn, free_from, LOOKUP_NODE);
> > > > > > if (err) {
> > > > > > if (err == -ENOENT)
> > > > > > goto free_next;
> > > > > > - f2fs_unlock_op(sbi);
> > > > > > + if (lock)
> > > > > > + f2fs_unlock_op(sbi);
> > > > > > trace_f2fs_truncate_blocks_exit(inode, err);
> > > > > > return err;
> > > > > > }
> > > > > > @@ -463,7 +465,8 @@ int truncate_blocks(struct inode *inode, u64 from)
> > > > > > f2fs_put_dnode(&dn);
> > > > > > free_next:
> > > > > > err = truncate_inode_blocks(inode, free_from);
> > > > > > - f2fs_unlock_op(sbi);
> > > > > > + if (lock)
> > > > > > + f2fs_unlock_op(sbi);
> > > > > > done:
> > > > > > /* lastly zero out the first data page */
> > > > > > truncate_partial_data_page(inode, from);
> > > > > > @@ -480,7 +483,7 @@ void f2fs_truncate(struct inode *inode)
> > > > > >
> > > > > > trace_f2fs_truncate(inode);
> > > > > >
> > > > > > - if (!truncate_blocks(inode, i_size_read(inode))) {
> > > > > > + if (!truncate_blocks(inode, i_size_read(inode), true)) {
> > > > > > inode->i_mtime = inode->i_ctime = CURRENT_TIME;
> > > > > > mark_inode_dirty(inode);
> > > > > > }
> > > > > > diff --git a/fs/f2fs/inline.c b/fs/f2fs/inline.c
> > > > > > index 520758b..4d1f39f 100644
> > > > > > --- a/fs/f2fs/inline.c
> > > > > > +++ b/fs/f2fs/inline.c
> > > > > > @@ -247,7 +247,7 @@ process_inline:
> > > > > > update_inode(inode, ipage);
> > > > > > f2fs_put_page(ipage, 1);
> > > > > > } else if (ri && (ri->i_inline & F2FS_INLINE_DATA)) {
> > > > > > - truncate_blocks(inode, 0);
> > > > > > + truncate_blocks(inode, 0, false);
> > > > > > set_inode_flag(F2FS_I(inode), FI_INLINE_DATA);
> > > > > > goto process_inline;
> > > > > > }
> > > > > > --
> > > > > > 1.8.5.2 (Apple Git-48)
> > > > > >
> > > > > >
> > > > > > ------------------------------------------------------------------------------
> > > > > > _______________________________________________
> > > > > > Linux-f2fs-devel mailing list
> > > > > > Linux-f2fs-devel@...ts.sourceforge.net
> > > > > > https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
> > > > >
> > > > >
> > > > > ------------------------------------------------------------------------------
> > > > > _______________________________________________
> > > > > Linux-f2fs-devel mailing list
> > > > > Linux-f2fs-devel@...ts.sourceforge.net
> > > > > https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
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