[{"id":3644721,"web_url":"http://patchwork.ozlabs.org/comment/3644721/","msgid":"","list_archive_url":null,"date":"2026-02-02T16:41:39","subject":"Re: [PATCH 2/3] ext4: use READ_ONCE for lockless jinode reads","submitter":{"id":363,"url":"http://patchwork.ozlabs.org/api/people/363/","name":"Jan Kara","email":"jack@suse.cz"},"content":"On Fri 30-01-26 11:12:31, Li Chen wrote:\n> ext4 journal commit callbacks access jbd2_inode fields such as\n> i_transaction and i_dirty_start/end without holding journal->j_list_lock.\n> \n> Use READ_ONCE() for these reads to correct the concurrency assumptions.\n> \n> Suggested-by: Jan Kara \n> Signed-off-by: Li Chen \n\nLooks good. Feel free to add:\n\nReviewed-by: Jan Kara \n\n\t\t\t\t\t\t\t\tHonza\n\n> ---\n> fs/ext4/inode.c | 6 ++++--\n> fs/ext4/super.c | 13 ++++++++-----\n> 2 files changed, 12 insertions(+), 7 deletions(-)\n> \n> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c\n> index d99296d7315f..2d451388e080 100644\n> --- a/fs/ext4/inode.c\n> +++ b/fs/ext4/inode.c\n> @@ -3033,11 +3033,13 @@ static int ext4_writepages(struct address_space *mapping,\n> \n> int ext4_normal_submit_inode_data_buffers(struct jbd2_inode *jinode)\n> {\n> +\tloff_t dirty_start = READ_ONCE(jinode->i_dirty_start);\n> +\tloff_t dirty_end = READ_ONCE(jinode->i_dirty_end);\n> \tstruct writeback_control wbc = {\n> \t\t.sync_mode = WB_SYNC_ALL,\n> \t\t.nr_to_write = LONG_MAX,\n> -\t\t.range_start = jinode->i_dirty_start,\n> -\t\t.range_end = jinode->i_dirty_end,\n> +\t\t.range_start = dirty_start,\n> +\t\t.range_end = dirty_end,\n> \t};\n> \tstruct mpage_da_data mpd = {\n> \t\t.inode = jinode->i_vfs_inode,\n> diff --git a/fs/ext4/super.c b/fs/ext4/super.c\n> index 5cf6c2b54bbb..acb2bc016fd4 100644\n> --- a/fs/ext4/super.c\n> +++ b/fs/ext4/super.c\n> @@ -521,6 +521,7 @@ static bool ext4_journalled_writepage_needs_redirty(struct jbd2_inode *jinode,\n> {\n> \tstruct buffer_head *bh, *head;\n> \tstruct journal_head *jh;\n> +\ttransaction_t *trans = READ_ONCE(jinode->i_transaction);\n> \n> \tbh = head = folio_buffers(folio);\n> \tdo {\n> @@ -539,7 +540,7 @@ static bool ext4_journalled_writepage_needs_redirty(struct jbd2_inode *jinode,\n> \t\t */\n> \t\tjh = bh2jh(bh);\n> \t\tif (buffer_dirty(bh) ||\n> -\t\t (jh && (jh->b_transaction != jinode->i_transaction ||\n> +\t\t (jh && (jh->b_transaction != trans ||\n> \t\t\t jh->b_next_transaction)))\n> \t\t\treturn true;\n> \t} while ((bh = bh->b_this_page) != head);\n> @@ -550,12 +551,14 @@ static bool ext4_journalled_writepage_needs_redirty(struct jbd2_inode *jinode,\n> static int ext4_journalled_submit_inode_data_buffers(struct jbd2_inode *jinode)\n> {\n> \tstruct address_space *mapping = jinode->i_vfs_inode->i_mapping;\n> +\tloff_t dirty_start = READ_ONCE(jinode->i_dirty_start);\n> +\tloff_t dirty_end = READ_ONCE(jinode->i_dirty_end);\n> \tstruct writeback_control wbc = {\n> -\t\t.sync_mode = WB_SYNC_ALL,\n> +\t\t.sync_mode = WB_SYNC_ALL,\n> \t\t.nr_to_write = LONG_MAX,\n> -\t\t.range_start = jinode->i_dirty_start,\n> -\t\t.range_end = jinode->i_dirty_end,\n> - };\n> +\t\t.range_start = dirty_start,\n> +\t\t.range_end = dirty_end,\n> +\t};\n> \tstruct folio *folio = NULL;\n> \tint error;\n> \n> -- \n> 2.52.0","headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linux-ext4@vger.kernel.org"],"Delivered-To":["patchwork-incoming@legolas.ozlabs.org","patchwork-incoming@ozlabs.org"],"Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=suse.cz header.i=@suse.cz header.a=rsa-sha256\n header.s=susede2_rsa header.b=153kQ41j;\n\tdkim=pass header.d=suse.cz header.i=@suse.cz header.a=ed25519-sha256\n header.s=susede2_ed25519 header.b=sZ71oRd1;\n\tdkim=pass (1024-bit key) header.d=suse.cz header.i=@suse.cz\n header.a=rsa-sha256 header.s=susede2_rsa header.b=153kQ41j;\n\tdkim=neutral header.d=suse.cz header.i=@suse.cz header.a=ed25519-sha256\n header.s=susede2_ed25519 header.b=sZ71oRd1;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=ozlabs.org\n (client-ip=2404:9400:2221:ea00::3; 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