Messages in this thread |  | | Date | Tue, 26 Nov 2024 22:49:14 +0800 | | Subject | Re: [PATCH v2 2/2] ext4: protect ext4_release_dquot against freezing | | From | Baokun Li <> |
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On 2024/11/21 20:38, Ojaswin Mujoo wrote: > Protect ext4_release_dquot against freezing so that we > don't try to start a transaction when FS is frozen, leading > to warnings. > > Further, avoid taking the freeze protection if a transaction > is already running so that we don't need end up in a deadlock > as described in > > 46e294efc355 ext4: fix deadlock with fs freezing and EA inodes > > Suggested-by: Jan Kara <jack@suse.cz> > Signed-off-by: Ojaswin Mujoo <ojaswin@linux.ibm.com> > --- > fs/ext4/super.c | 17 +++++++++++++++++ > 1 file changed, 17 insertions(+) > > diff --git a/fs/ext4/super.c b/fs/ext4/super.c > index 16a4ce704460..f7437a592359 100644 > --- a/fs/ext4/super.c > +++ b/fs/ext4/super.c > @@ -6887,12 +6887,25 @@ static int ext4_release_dquot(struct dquot *dquot) > { > int ret, err; > handle_t *handle; > + bool freeze_protected = false; > + > + /* > + * Trying to sb_start_intwrite() in a running transaction > + * can result in a deadlock. Further, running transactions > + * are already protected from freezing. > + */ > + if (!ext4_journal_current_handle()) { > + sb_start_intwrite(dquot->dq_sb); > + freeze_protected = true; > + } > > handle = ext4_journal_start(dquot_to_inode(dquot), EXT4_HT_QUOTA, > EXT4_QUOTA_DEL_BLOCKS(dquot->dq_sb)); > if (IS_ERR(handle)) { > /* Release dquot anyway to avoid endless cycle in dqput() */ > dquot_release(dquot); > + if (freeze_protected) > + sb_end_intwrite(dquot->dq_sb); > return PTR_ERR(handle); > } > ret = dquot_release(dquot); > @@ -6903,6 +6916,10 @@ static int ext4_release_dquot(struct dquot *dquot) The `git am` command looks for the following context code from line 6903 to apply the changes. But there are many functions in fs/ext4/super.c that have similar code, such as ext4_write_dquot() and ext4_acquire_dquot().
So when the code before ext4_release_dquot() is added, the first matching context found could be in ext4_write_dquot() or ext4_acquire_dquot(). > err = ext4_journal_stop(handle); > if (!ret) > ret = err; > + > + if (freeze_protected) > + sb_end_intwrite(dquot->dq_sb); > + > return ret; > } >
Thus this is actually a bug in `git am`, which can be avoided by increasing the number of context lines with `git format-patch -U8 -1`.
Otherwise it looks good. Feel free to add:
Reviewed-by: Baokun Li <libaokun1@huawei.com>
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