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GET /api/1.2/patches/2186634/?format=api
HTTP 200 OK
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Content-Type: application/json
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{
    "id": 2186634,
    "url": "http://patchwork.ozlabs.org/api/1.2/patches/2186634/?format=api",
    "web_url": "http://patchwork.ozlabs.org/project/linux-ext4/patch/20260120112538.132774-3-me@linux.beauty/",
    "project": {
        "id": 8,
        "url": "http://patchwork.ozlabs.org/api/1.2/projects/8/?format=api",
        "name": "Linux ext4 filesystem development",
        "link_name": "linux-ext4",
        "list_id": "linux-ext4.vger.kernel.org",
        "list_email": "linux-ext4@vger.kernel.org",
        "web_url": null,
        "scm_url": null,
        "webscm_url": null,
        "list_archive_url": "",
        "list_archive_url_format": "",
        "commit_url_format": ""
    },
    "msgid": "<20260120112538.132774-3-me@linux.beauty>",
    "list_archive_url": null,
    "date": "2026-01-20T11:25:31",
    "name": "[RFC,v4,2/7] ext4: lockdep: handle i_data_sem subclassing for special inodes",
    "commit_ref": null,
    "pull_url": null,
    "state": "superseded",
    "archived": false,
    "hash": "5d684ead445116215d627590765107565a8360d8",
    "submitter": {
        "id": 84264,
        "url": "http://patchwork.ozlabs.org/api/1.2/people/84264/?format=api",
        "name": "Li Chen",
        "email": "me@linux.beauty"
    },
    "delegate": null,
    "mbox": "http://patchwork.ozlabs.org/project/linux-ext4/patch/20260120112538.132774-3-me@linux.beauty/mbox/",
    "series": [
        {
            "id": 489032,
            "url": "http://patchwork.ozlabs.org/api/1.2/series/489032/?format=api",
            "web_url": "http://patchwork.ozlabs.org/project/linux-ext4/list/?series=489032",
            "date": "2026-01-20T11:25:32",
            "name": "ext4: fast commit: snapshot inode state for FC log",
            "version": 4,
            "mbox": "http://patchwork.ozlabs.org/series/489032/mbox/"
        }
    ],
    "comments": "http://patchwork.ozlabs.org/api/patches/2186634/comments/",
    "check": "pending",
    "checks": "http://patchwork.ozlabs.org/api/patches/2186634/checks/",
    "tags": {},
    "related": [],
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        ],
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        "From": "Li Chen <me@linux.beauty>",
        "To": "Zhang Yi <yi.zhang@huaweicloud.com>,\n\t\"Theodore Ts'o\" <tytso@mit.edu>,\n\tAndreas Dilger <adilger.kernel@dilger.ca>,\n\tlinux-ext4@vger.kernel.org,\n\tlinux-kernel@vger.kernel.org",
        "Cc": "Li Chen <me@linux.beauty>",
        "Subject": "[RFC v4 2/7] ext4: lockdep: handle i_data_sem subclassing for special\n inodes",
        "Date": "Tue, 20 Jan 2026 19:25:31 +0800",
        "Message-ID": "<20260120112538.132774-3-me@linux.beauty>",
        "X-Mailer": "git-send-email 2.52.0",
        "In-Reply-To": "<20260120112538.132774-1-me@linux.beauty>",
        "References": "<20260120112538.132774-1-me@linux.beauty>",
        "Precedence": "bulk",
        "X-Mailing-List": "linux-ext4@vger.kernel.org",
        "List-Id": "<linux-ext4.vger.kernel.org>",
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        "X-ZohoMailClient": "External",
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        "X-Spam-Checker-Version": "SpamAssassin 4.0.1 (2024-03-25) on gandalf.ozlabs.org"
    },
    "content": "Fast commit can hold s_fc_lock while writing journal blocks. Mapping the\njournal inode can take its i_data_sem. Normal inode update paths can take a\ndata inode i_data_sem and then s_fc_lock, which makes lockdep report a\ncircular dependency.\n\nlockdep treats all i_data_sem instances as one lock class and cannot\ndistinguish the journal inode i_data_sem from a regular inode i_data_sem.\nThe journal inode is not tracked by fast commit and no FC waiters ever\ndepend on it, so this is not a real ABBA deadlock. Assign the journal inode\na dedicated i_data_sem lockdep subclass to avoid the false positive.\n\nInode cache objects can be recycled, so also reset i_data_sem to\nI_DATA_SEM_NORMAL when allocating an ext4 inode. Otherwise a new inode may\ninherit an old subclass (journal/quota/ea) and trigger lockdep warnings.\n\nSigned-off-by: Li Chen <me@linux.beauty>\n---\n fs/ext4/ext4.h  | 4 +++-\n fs/ext4/super.c | 8 ++++++++\n 2 files changed, 11 insertions(+), 1 deletion(-)",
    "diff": "diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h\nindex bd30c24d4f94..2e1681057196 100644\n--- a/fs/ext4/ext4.h\n+++ b/fs/ext4/ext4.h\n@@ -1025,12 +1025,14 @@ do {\t\t\t\t\t\t\t\t\t\t\\\n  *\t\t\t  than the first\n  *  I_DATA_SEM_QUOTA  - Used for quota inodes only\n  *  I_DATA_SEM_EA     - Used for ea_inodes only\n+ *  I_DATA_SEM_JOURNAL - Used for journal inode only\n  */\n enum {\n \tI_DATA_SEM_NORMAL = 0,\n \tI_DATA_SEM_OTHER,\n \tI_DATA_SEM_QUOTA,\n-\tI_DATA_SEM_EA\n+\tI_DATA_SEM_EA,\n+\tI_DATA_SEM_JOURNAL\n };\n \n struct ext4_fc_inode_snap;\ndiff --git a/fs/ext4/super.c b/fs/ext4/super.c\nindex 79762c3e0dff..4f5f0c21d436 100644\n--- a/fs/ext4/super.c\n+++ b/fs/ext4/super.c\n@@ -1423,6 +1423,9 @@ static struct inode *ext4_alloc_inode(struct super_block *sb)\n \tINIT_WORK(&ei->i_rsv_conversion_work, ext4_end_io_rsv_work);\n \text4_fc_init_inode(&ei->vfs_inode);\n \tspin_lock_init(&ei->i_fc_lock);\n+#ifdef CONFIG_LOCKDEP\n+\tlockdep_set_subclass(&ei->i_data_sem, I_DATA_SEM_NORMAL);\n+#endif\n \treturn &ei->vfs_inode;\n }\n \n@@ -5863,6 +5866,11 @@ static struct inode *ext4_get_journal_inode(struct super_block *sb,\n \t\treturn ERR_PTR(-EFSCORRUPTED);\n \t}\n \n+#ifdef CONFIG_LOCKDEP\n+\tlockdep_set_subclass(&EXT4_I(journal_inode)->i_data_sem,\n+\t\t\t     I_DATA_SEM_JOURNAL);\n+#endif\n+\n \text4_debug(\"Journal inode found at %p: %lld bytes\\n\",\n \t\t  journal_inode, journal_inode->i_size);\n \treturn journal_inode;\n",
    "prefixes": [
        "RFC",
        "v4",
        "2/7"
    ]
}