841aee4d75
Put NVMe/TCP sockets in their own class to avoid some lockdep warnings. Sockets created by nvme-tcp are not exposed to user-space, and will not trigger certain code paths that the general socket API exposes. Lockdep complains about a circular dependency between the socket and filesystem locks, because setsockopt can trigger a page fault with a socket lock held, but nvme-tcp sends requests on the socket while file system locks are held. ====================================================== WARNING: possible circular locking dependency detected 5.15.0-rc3 #1 Not tainted ------------------------------------------------------ fio/1496 is trying to acquire lock: (sk_lock-AF_INET){+.+.}-{0:0}, at: tcp_sendpage+0x23/0x80 but task is already holding lock: (&xfs_dir_ilock_class/5){+.+.}-{3:3}, at: xfs_ilock+0xcf/0x290 [xfs] which lock already depends on the new lock. other info that might help us debug this: chain exists of: sk_lock-AF_INET --> sb_internal --> &xfs_dir_ilock_class/5 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&xfs_dir_ilock_class/5); lock(sb_internal); lock(&xfs_dir_ilock_class/5); lock(sk_lock-AF_INET); *** DEADLOCK *** 6 locks held by fio/1496: #0: (sb_writers#13){.+.+}-{0:0}, at: path_openat+0x9fc/0xa20 #1: (&inode->i_sb->s_type->i_mutex_dir_key){++++}-{3:3}, at: path_openat+0x296/0xa20 #2: (sb_internal){.+.+}-{0:0}, at: xfs_trans_alloc_icreate+0x41/0xd0 [xfs] #3: (&xfs_dir_ilock_class/5){+.+.}-{3:3}, at: xfs_ilock+0xcf/0x290 [xfs] #4: (hctx->srcu){....}-{0:0}, at: hctx_lock+0x51/0xd0 #5: (&queue->send_mutex){+.+.}-{3:3}, at: nvme_tcp_queue_rq+0x33e/0x380 [nvme_tcp] This annotation lets lockdep analyze nvme-tcp controlled sockets independently of what the user-space sockets API does. Link: https://lore.kernel.org/linux-nvme/CAHj4cs9MDYLJ+q+2_GXUK9HxFizv2pxUryUR0toX974M040z7g@mail.gmail.com/ Signed-off-by: Chris Leech <cleech@redhat.com> Signed-off-by: Christoph Hellwig <hch@lst.de>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.