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Date: Tue, 3 Nov 2020 15:46:46 +0100
From: Jan Kara <jack@...e.cz>
To: Harshad Shirwadkar <harshadshirwadkar@...il.com>
Cc: linux-ext4@...r.kernel.org, tytso@....edu, jack@...e.cz
Subject: Re: [PATCH 03/10] ext4: pass handle to ext4_fc_track_* functions
On Sat 31-10-20 13:05:11, Harshad Shirwadkar wrote:
> Use transaction id found in handle->h_transaction->h_tid for tracking
> fast commit updates. This patch also restructures ext4_unlink to make
> handle available inside ext4_unlink for fast commit tracking.
>
> Suggested-by: Jan Kara <jack@...e.cz>
> Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@...il.com>
Thanks for the patch. Couple of comments below:
> @@ -4651,8 +4652,6 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
> FALLOC_FL_COLLAPSE_RANGE | FALLOC_FL_ZERO_RANGE |
> FALLOC_FL_INSERT_RANGE))
> return -EOPNOTSUPP;
> - ext4_fc_track_range(inode, offset >> blkbits,
> - (offset + len - 1) >> blkbits);
Why do you delete the ext4_fc_track_range() call here?
> diff --git a/fs/ext4/fast_commit.c b/fs/ext4/fast_commit.c
> index 354f81ff819d..5c3af472287a 100644
> --- a/fs/ext4/fast_commit.c
> +++ b/fs/ext4/fast_commit.c
> @@ -323,15 +323,18 @@ static inline int ext4_fc_is_ineligible(struct super_block *sb)
> * If enqueue is set, this function enqueues the inode in fast commit list.
> */
> static int ext4_fc_track_template(
> - struct inode *inode, int (*__fc_track_fn)(struct inode *, void *, bool),
> + handle_t *handle, struct inode *inode,
> + int (*__fc_track_fn)(struct inode *, void *, bool),
> void *args, int enqueue)
> {
> - tid_t running_txn_tid;
> bool update = false;
> struct ext4_inode_info *ei = EXT4_I(inode);
> struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
> + tid_t tid = 0;
> int ret;
>
> + if (ext4_handle_valid(handle) && handle->h_transaction)
> + tid = handle->h_transaction->t_tid;
The handle->h_transaction check is pointless here. It is always true. And
if you move the tid fetching after the JOURNAL_FAST_COMMIT check below, you
don't need the ext4_handle_valid() check either as fastcommit cannot be
enabled without a journal.
> if (!test_opt2(inode->i_sb, JOURNAL_FAST_COMMIT) ||
> (sbi->s_mount_state & EXT4_FC_REPLAY))
> return -EOPNOTSUPP;
> diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
> index 5159830dacb8..f3f8bf61072e 100644
> --- a/fs/ext4/namei.c
> +++ b/fs/ext4/namei.c
> @@ -2631,7 +2631,7 @@ static int ext4_create(struct inode *dir, struct dentry *dentry, umode_t mode,
> inode_save = inode;
> ihold(inode_save);
> err = ext4_add_nondir(handle, dentry, &inode);
> - ext4_fc_track_create(inode_save, dentry);
> + ext4_fc_track_create(handle, inode_save, dentry);
> iput(inode_save);
> }
> if (handle)
> @@ -2668,7 +2668,7 @@ static int ext4_mknod(struct inode *dir, struct dentry *dentry,
> ihold(inode_save);
> err = ext4_add_nondir(handle, dentry, &inode);
> if (!err)
> - ext4_fc_track_create(inode_save, dentry);
> + ext4_fc_track_create(handle, inode_save, dentry);
> iput(inode_save);
> }
Not directly related to this patch but why do you bother with 'inode_save'
in the above cases? I guess you're afraid by the comment that "inode
reference is consumed by the dentry" but since you have a dentry reference
as well, you can be sure that the inode stays around...
> if (handle)
> @@ -2833,7 +2833,7 @@ static int ext4_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
> iput(inode);
> goto out_retry;
> }
> - ext4_fc_track_create(inode, dentry);
> + ext4_fc_track_create(handle, inode, dentry);
> ext4_inc_count(dir);
And I was also wondering why all the directory tracking functions take both
dentry and the inode. You can fetch inode from a dentry with d_inode()
helper so I don't see a reason for passing it separately. That is, in a
couple of places you call ext4_fc_track_*() before d_instantiate[_new]() so
dentry isn't fully setup yet but there's nothing which prevents you from
calling it after d_instantiate().
The only possible exception to this is the ext4_rename() code. There you
don't have suitable dentry for the link tracking so this would need to
explicitely pass the inode & dentry. But that place can just call a low
level wrapper allowing that. All the other places can use a higher level
function which just takes the dentry.
> static int ext4_unlink(struct inode *dir, struct dentry *dentry)
> {
> + handle_t *handle;
> int retval;
>
> if (unlikely(ext4_forced_shutdown(EXT4_SB(dir->i_sb))))
> @@ -3282,9 +3273,16 @@ static int ext4_unlink(struct inode *dir, struct dentry *dentry)
> if (retval)
> goto out_trace;
>
> - retval = __ext4_unlink(dir, &dentry->d_name, d_inode(dentry));
> + handle = ext4_journal_start(dir, EXT4_HT_DIR,
> + EXT4_DATA_TRANS_BLOCKS(dir->i_sb));
> + if (IS_ERR(handle)) {
> + retval = PTR_ERR(handle);
> + goto out_trace;
> + }
> +
> + retval = __ext4_unlink(handle, dir, &dentry->d_name, d_inode(dentry));
> if (!retval)
> - ext4_fc_track_unlink(d_inode(dentry), dentry);
> + ext4_fc_track_unlink(handle, d_inode(dentry), dentry);
> #ifdef CONFIG_UNICODE
> /* VFS negative dentries are incompatible with Encoding and
> * Case-insensitiveness. Eventually we'll want avoid
> @@ -3295,6 +3293,8 @@ static int ext4_unlink(struct inode *dir, struct dentry *dentry)
> if (IS_CASEFOLDED(dir))
> d_invalidate(dentry);
> #endif
> + if (handle)
> + ext4_journal_stop(handle);
How could 'handle' be NULL here?
Honza
--
Jan Kara <jack@...e.com>
SUSE Labs, CR
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