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@xxxxxxx> Signed-off-by: Ojaswin Mujoo <ojaswin@xxxxxxxxxxxxx> --- 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@xxxxxxxxxx>
