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Date:   Wed, 19 Aug 2020 10:46:30 +0200
From:   Jan Kara <jack@suse.cz>
To:     Mauricio Faria de Oliveira <mfo@canonical.com>
Cc:     Jan Kara <jack@suse.cz>, linux-ext4@vger.kernel.org,
        dann frazier <dann.frazier@canonical.com>,
        Mauricio Faria de Oliveira <mauricio.foliveira@gmail.com>,
        Jan Kara <jack@suse.com>
Subject: Re: [RFC PATCH v2 5/5] ext4/jbd2: debugging messages
Message-ID: <20200819084629.GE1902@quack2.suse.cz>
References: <20200810010210.3305322-1-mfo@canonical.com>
 <20200810010210.3305322-6-mfo@canonical.com>
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On Sun 09-08-20 22:02:08, Mauricio Faria de Oliveira wrote:
> For code tracking and deubgging purposes; some used in cover letter.

Again, this is nice for debugging but for official submission, keep this
patch separate because it should not get merged...

								Honza
> 
> ---
>  fs/ext4/inode.c       | 27 +++++++++++++++++++++++++++
>  fs/ext4/super.c       | 10 ++++++++++
>  fs/jbd2/commit.c      |  5 +++++
>  fs/jbd2/journal.c     |  5 +++++
>  fs/jbd2/transaction.c |  4 ++++
>  5 files changed, 51 insertions(+)
> 
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index ce5464f92a7e..cd01aec87303 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -48,6 +48,17 @@
>  
>  #include <trace/events/ext4.h>
>  
> +#include "ext4_jbd2_dbg.h"
> +
> +static int ext4_bh_tdbg(handle_t *handle, struct buffer_head *bh)
> +{
> +	struct super_block *sb = bh->b_page->mapping->host->i_sb;
> +	tdbg_ext4(sb, "bh: %px, data offset: %04llx, page: %px, inode: %px\n",
> +		  bh, (u64) bh->b_data & ((u64)PAGE_SIZE - 1),
> +		  bh->b_page, bh->b_page->mapping->host);
> +	return 0;
> +}
> +
>  static __u32 ext4_inode_csum(struct inode *inode, struct ext4_inode *raw,
>  			      struct ext4_inode_info *ei)
>  {
> @@ -1193,6 +1204,7 @@ static int ext4_write_begin(struct file *file, struct address_space *mapping,
>  		ret = __block_write_begin(page, pos, len, ext4_get_block);
>  #endif
>  	if (!ret && ext4_should_journal_data(inode)) {
> +		tdbg_ext4(inode->i_sb, "journal started: inode %px, txn %px", inode, handle->h_transaction);
>  		ret = ext4_walk_page_buffers(handle, page_buffers(page),
>  					     from, to, NULL,
>  					     do_journal_get_write_access);
> @@ -1446,6 +1458,7 @@ static int ext4_journalled_write_end(struct file *file,
>  			ext4_orphan_del(NULL, inode);
>  	}
>  
> +	tdbg_ext4(inode->i_sb, "journal stopped: inode %px", inode);
>  	return ret ? ret : copied;
>  }
>  
> @@ -1917,6 +1930,10 @@ static int __ext4_journalled_writepage(struct page *page,
>  	err = ext4_jbd2_inode_add_write(handle, inode, 0, len);
>  	if (ret == 0)
>  		ret = err;
> +	{
> +		struct super_block *sb = handle->h_transaction->t_journal->j_private;
> +		tdbg_ext4(sb, "Added inode to txn list: inode %px, txn = %px, err = %d", inode, handle->h_transaction, err);
> +	}
>  	EXT4_I(inode)->i_datasync_tid = handle->h_transaction->t_tid;
>  	err = ext4_journal_stop(handle);
>  	if (!ret)
> @@ -2035,6 +2052,7 @@ static int ext4_writepage(struct page *page,
>  		keep_towrite = true;
>  	}
>  
> +	tdbg_ext4(inode->i_sb, "called for inode %px by comm %s", inode, current->comm);
>  	if (PageChecked(page) && ext4_should_journal_data(inode))
>  		/*
>  		 * It's mmapped pagecache.  Add buffers and journal it.  There
> @@ -5969,6 +5987,8 @@ vm_fault_t ext4_page_mkwrite(struct vm_fault *vmf)
>  	get_block_t *get_block;
>  	int retries = 0;
>  
> +	tdbg_ext4(inode->i_sb, "entry for inode %px", inode);
> +
>  	if (unlikely(IS_IMMUTABLE(inode)))
>  		return VM_FAULT_SIGBUS;
>  
> @@ -6006,6 +6026,9 @@ vm_fault_t ext4_page_mkwrite(struct vm_fault *vmf)
>  		len = size & ~PAGE_MASK;
>  	else
>  		len = PAGE_SIZE;
> +
> +	ext4_walk_page_buffers(NULL, page_buffers(page), 0, len, NULL, ext4_bh_tdbg);
> +
>  	/*
>  	 * Return if we have all the buffers mapped. This avoids the need to do
>  	 * journal_start/journal_stop which can block and take a long time. But
> @@ -6018,6 +6041,7 @@ vm_fault_t ext4_page_mkwrite(struct vm_fault *vmf)
>  			/* Wait so that we don't change page under IO */
>  			wait_for_stable_page(page);
>  			ret = VM_FAULT_LOCKED;
> +			tdbg_ext4(inode->i_sb, "returning; all buffers mapped for inode %px", inode);
>  			goto out;
>  		}
>  	}
> @@ -6036,6 +6060,7 @@ vm_fault_t ext4_page_mkwrite(struct vm_fault *vmf)
>  	}
>  	err = block_page_mkwrite(vma, vmf, get_block);
>  	if (!err && ext4_should_journal_data(inode)) {
> +		tdbg_ext4(inode->i_sb, "before djgwa(), for inode %px", inode);
>  		if (ext4_walk_page_buffers(handle, page_buffers(page), 0,
>  			  PAGE_SIZE, NULL, do_journal_get_write_access)) {
>  			unlock_page(page);
> @@ -6043,6 +6068,7 @@ vm_fault_t ext4_page_mkwrite(struct vm_fault *vmf)
>  			ext4_journal_stop(handle);
>  			goto out;
>  		}
> +		tdbg_ext4(inode->i_sb, "after  djgwa(), for inode %px", inode);
>  		ext4_set_inode_state(inode, EXT4_STATE_JDATA);
>  		if (ext4_jbd2_inode_add_write(handle, inode, 0, PAGE_SIZE)) {
>  			unlock_page(page);
> @@ -6050,6 +6076,7 @@ vm_fault_t ext4_page_mkwrite(struct vm_fault *vmf)
>  			ext4_journal_stop(handle);
>  			goto out;
>  		}
> +		tdbg_ext4(inode->i_sb, "Added inode to txn list: inode %px, txn = %px, err = 0", inode, handle->h_transaction);
>  	}
>  	ext4_journal_stop(handle);
>  	if (err == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 38aaac6572ea..7167fcf60b5c 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -58,6 +58,8 @@
>  #define CREATE_TRACE_POINTS
>  #include <trace/events/ext4.h>
>  
> +#include "ext4_jbd2_dbg.h"
> +
>  static struct ext4_lazy_init *ext4_li_info;
>  static struct mutex ext4_li_mtx;
>  static struct ratelimit_state ext4_mount_msg_ratelimit;
> @@ -492,14 +494,20 @@ static int ext4_journalled_writepage_callback(struct page *page,
>  	transaction_t *transaction = (transaction_t *) data;
>  	struct buffer_head *bh, *head;
>  	struct journal_head *jh;
> +	struct super_block *sb = page->mapping->host->i_sb;
>  
>  	// XXX: any chance of !bh here?
>  	bh = head = page_buffers(page);
> +	tdbg_ext4(sb, "entry for bh %px, page %px, inode: %px", bh, page, page->mapping->host);
>  	do {
>  		jh = bh2jh(bh);
>  		if (!jh || jh->b_transaction != transaction ||
>  		    jh->b_next_transaction) {
>  			redirty_page_for_writepage(wbc, page);
> +			tdbg_ext4(sb, "redirty for bh %px, jh, %px, txn %px, next_txn %px",
> +				  bh, jh,
> +				  jh ? jh->b_transaction : NULL,
> +				  jh ? jh->b_next_transaction : NULL);
>  			goto out;
>  		}
>  	} while ((bh = bh->b_this_page) != head);
> @@ -522,6 +530,7 @@ static int ext4_journalled_submit_inode_data_buffers(struct jbd2_inode *jinode)
>  		.range_end = dirty_end,
>          };
>  
> +	tdbg_ext4(jinode->i_vfs_inode->i_sb, "entry for inode: %px", jinode->i_vfs_inode);
>  	return write_cache_pages(mapping, &wbc,
>  				 ext4_journalled_writepage_callback,
>  				 transaction);
> @@ -529,6 +538,7 @@ static int ext4_journalled_submit_inode_data_buffers(struct jbd2_inode *jinode)
>  
>  static int ext4_journalled_finish_inode_data_buffers(struct jbd2_inode *jinode)
>  {
> +	tdbg_ext4(jinode->i_vfs_inode->i_sb, "entry for inode: %px", jinode->i_vfs_inode);
>  	return 0;
>  }
>  
> diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
> index b98d227b50d8..96f0d81eadf9 100644
> --- a/fs/jbd2/commit.c
> +++ b/fs/jbd2/commit.c
> @@ -29,6 +29,8 @@
>  #include <linux/printk.h>
>  #include <linux/delay.h>
>  
> +#include "../ext4/ext4_jbd2_dbg.h"
> +
>  static journal_t *force_panic;
>  
>  /*
> @@ -222,11 +224,14 @@ static int journal_submit_data_buffers(journal_t *journal,
>  	int err, ret = 0;
>  	struct address_space *mapping;
>  
> +	tdbg_jbd2(journal, "entry for transaction: 0x%px\n", commit_transaction);
>  	spin_lock(&journal->j_list_lock);
>  	list_for_each_entry(jinode, &commit_transaction->t_inode_list, i_list) {
>  		loff_t dirty_start = jinode->i_dirty_start;
>  		loff_t dirty_end = jinode->i_dirty_end;
>  
> +		tdbg_jbd2(journal, "txn list has inode %px (write data flag: 0x%lx)\n", jinode->i_vfs_inode, (jinode->i_flags & JI_WRITE_DATA));
> +
>  		if (!(jinode->i_flags & JI_WRITE_DATA))
>  			continue;
>  		mapping = jinode->i_vfs_inode->i_mapping;
> diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
> index e4944436e733..b86b871ee823 100644
> --- a/fs/jbd2/journal.c
> +++ b/fs/jbd2/journal.c
> @@ -48,6 +48,8 @@
>  #include <linux/uaccess.h>
>  #include <asm/page.h>
>  
> +#include "../ext4/ext4_jbd2_dbg.h"
> +
>  #ifdef CONFIG_JBD2_DEBUG
>  ushort jbd2_journal_enable_debug __read_mostly;
>  EXPORT_SYMBOL(jbd2_journal_enable_debug);
> @@ -453,6 +455,9 @@ int jbd2_journal_write_metadata_buffer(transaction_t *transaction,
>  
>  	*bh_out = new_bh;
>  
> +	tdbg_jbd2(transaction->t_journal, "copy out: done/need %d/%d, bh: %px, offset: %04x, page: %px, inode: %px\n",
> +	     done_copy_out, need_copy_out, jh2bh(jh_in), new_offset, new_page, new_page->mapping ? new_page->mapping->host : NULL);
> +
>  	/*
>  	 * The to-be-written buffer needs to get moved to the io queue,
>  	 * and the original buffer whose contents we are shadowing or
> diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
> index e91aad3637a2..93a55a228e08 100644
> --- a/fs/jbd2/transaction.c
> +++ b/fs/jbd2/transaction.c
> @@ -30,6 +30,8 @@
>  
>  #include <trace/events/jbd2.h>
>  
> +#include "../ext4/ext4_jbd2_dbg.h"
> +
>  static void __jbd2_journal_temp_unlink_buffer(struct journal_head *jh);
>  static void __jbd2_journal_unfile_buffer(struct journal_head *jh);
>  
> @@ -952,6 +954,8 @@ do_get_write_access(handle_t *handle, struct journal_head *jh,
>  repeat:
>  	bh = jh2bh(jh);
>  
> +	tdbg_jbd2(journal, "entry for bh: %px, offset: %04lx, page %px, inode: %px",
> +		  bh, offset_in_page(bh->b_data), bh->b_page, bh->b_page->mapping->host);
>  	/* @@@ Need to check for errors here at some point. */
>  
>   	start_lock = jiffies;
> -- 
> 2.17.1
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR