linux-ext4 - [RFC PATCH 08/11] ext4: data=journal: prevent journalled writeback deadlock in ext4_convert_inline_data_to

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Message-Id: <20200423233705.5878-9-mfo@canonical.com>
Date:   Thu, 23 Apr 2020 20:37:02 -0300
From:   Mauricio Faria de Oliveira <mfo@...onical.com>
To:     linux-ext4@...r.kernel.org, "Theodore Y. Ts'o" <tytso@....edu>
Cc:     dann frazier <dann.frazier@...onical.com>,
        Andreas Dilger <adilger@...ger.ca>, Jan Kara <jack@...e.com>
Subject: [RFC PATCH 08/11] ext4: data=journal: prevent journalled writeback deadlock in ext4_convert_inline_data_to_extent()

This patch checks for and prevents the deadlock with a page in
journalled writeback in ext4_convert_inline_data_to_extent().

Finally, add wait_on_page_writeback() if data=journal mode.

Note: similar changes are not needed in ext4_da_convert_inline_data_to_extent()
as delayed allocation is not applicable to data journalling
(different struct address_space_operations).

Signed-off-by: Mauricio Faria de Oliveira <mfo@...onical.com>
---
 fs/ext4/inline.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/fs/ext4/inline.c b/fs/ext4/inline.c
index 5fd275098d10..10665b066bb7 100644
--- a/fs/ext4/inline.c
+++ b/fs/ext4/inline.c
@@ -562,6 +562,8 @@ static int ext4_convert_inline_data_to_extent(struct address_space *mapping,
 		handle = NULL;
 		goto out;
 	}
+	if (ext4_should_journal_data(inode))
+		wait_on_page_writeback(page);
 	unlock_page(page);
 
 retry_journal:
@@ -581,9 +583,19 @@ static int ext4_convert_inline_data_to_extent(struct address_space *mapping,
 		put_page(page);
 		ext4_journal_stop(handle);
 		goto retry_grab;
+	} else if (ext4_should_journal_data(inode) &&
+		   ext4_check_journalled_writeback(handle, page)) {
+		/* Or transaction may block page writeback */
+		unlock_page(page);
+		put_page(page);
+		ext4_journal_stop(handle);
+		ext4_start_commit_datasync(inode);
+		goto retry_grab;
 	}
 	/* In case writeback began while the page was unlocked */
 	wait_for_stable_page(page);
+	if (ext4_should_journal_data(inode))
+		wait_on_page_writeback(page);
 
 	ext4_write_lock_xattr(inode, &no_expand);
 	sem_held = 1;
-- 
2.20.1