[{"id":3675050,"web_url":"http://patchwork.ozlabs.org/comment/3675050/","msgid":"<6864da80-b244-4444-aecd-2555c2d60db0@huaweicloud.com>","list_archive_url":null,"date":"2026-04-09T02:45:14","subject":"Re: [PATCH] jbd2: fix deadlock in jbd2_journal_cancel_revoke()","submitter":{"id":85428,"url":"http://patchwork.ozlabs.org/api/people/85428/","name":"Zhang Yi","email":"yi.zhang@huaweicloud.com"},"content":"Please ignore this patch; this solution does not correct.\n\nBest Regards.\nYi.\n\nOn 4/9/2026 9:07 AM, Zhang Yi wrote:\n> From: Zhang Yi \n> \n> Commit f76d4c28a46a (\"fs/jbd2: use sleeping version of\n> __find_get_block()\") changed jbd2_journal_cancel_revoke() to use\n> __find_get_block_nonatomic() which holds the folio lock instead of\n> i_private_lock. This breaks the lock ordering (folio -> buffer) and\n> causes an ABBA deadlock when the filesystem blocksize < pagesize:\n> \n> T1 T2\n> ext4_mkdir()\n> ext4_init_new_dir()\n> ext4_append()\n> ext4_getblk()\n> lock_buffer() <- A\n> sync_blockdev()\n> blkdev_writepages()\n> writeback_iter()\n> writeback_get_folio()\n> folio_lock() <- B\n> ext4_journal_get_create_access()\n> jbd2_journal_cancel_revoke()\n> __find_get_block_nonatomic()\n> folio_lock() <- B\n> block_write_full_folio()\n> lock_buffer() <- A\n> \n> This can occasionally cause generic/013 to hang.\n> \n> Fix by only calling __find_get_block_nonatomic() when the passed\n> buffer_head doesn't belong to the bdev (i.e., !bh->b_bdev), which is the\n> only case that we need to look up its bdev alias. Otherwise, the lookup\n> is redundant since the found buffer_head is equal to the one we passed\n> in.\n> \n> Fixes: f76d4c28a46a (\"fs/jbd2: use sleeping version of __find_get_block()\")\n> Signed-off-by: Zhang Yi \n> ---\n> fs/jbd2/revoke.c | 7 ++++---\n> 1 file changed, 4 insertions(+), 3 deletions(-)\n> \n> diff --git a/fs/jbd2/revoke.c b/fs/jbd2/revoke.c\n> index 9016ddb82447..8b52d40c27c9 100644\n> --- a/fs/jbd2/revoke.c\n> +++ b/fs/jbd2/revoke.c\n> @@ -464,13 +464,14 @@ void jbd2_journal_cancel_revoke(handle_t *handle, struct journal_head *jh)\n> \t * buffer_head? If so, we'd better make sure we clear the\n> \t * revoked status on any hashed alias too, otherwise the revoke\n> \t * state machine will get very upset later on. */\n> -\tif (need_cancel) {\n> +\tif (need_cancel && !bh->b_bdev) {\n> \t\tstruct buffer_head *bh2;\n> +\n> \t\tbh2 = __find_get_block_nonatomic(bh->b_bdev, bh->b_blocknr,\n> \t\t\t\t\t\t bh->b_size);\n> \t\tif (bh2) {\n> -\t\t\tif (bh2 != bh)\n> -\t\t\t\tclear_buffer_revoked(bh2);\n> +\t\t\tWARN_ON_ONCE(bh2 == bh);\n> +\t\t\tclear_buffer_revoked(bh2);\n> \t\t\t__brelse(bh2);\n> \t\t}\n> \t}","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 spf=pass (sender SPF authorized) smtp.mailfrom=ozlabs.org\n (client-ip=150.107.74.76; helo=mail.ozlabs.org;\n envelope-from=srs0=q3og=ci=vger.kernel.org=linux-ext4+bounces-15691-patchwork-incoming=ozlabs.org@ozlabs.org;\n receiver=patchwork.ozlabs.org)","gandalf.ozlabs.org;\n arc=pass smtp.remote-ip=172.234.253.10 arc.chain=subspace.kernel.org","gandalf.ozlabs.org;\n dmarc=none (p=none dis=none) header.from=huaweicloud.com","gandalf.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org\n (client-ip=172.234.253.10; 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