From: Jeff Layton <jlayton@kernel.org>
To: ira.weiny@intel.com, Andrew Morton <akpm@linux-foundation.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>,
Dan Williams <dan.j.williams@intel.com>,
Matthew Wilcox <willy@infradead.org>, Jan Kara <jack@suse.cz>,
Theodore Ts'o <tytso@mit.edu>, John Hubbard <jhubbard@nvidia.com>,
Michal Hocko <mhocko@suse.com>,
Dave Chinner <david@fromorbit.com>,
linux-xfs@vger.kernel.org, linux-rdma@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-nvdimm@lists.01.org, linux-ext4@vger.kernel.org,
linux-mm@kvack.org
Subject: Re: [RFC PATCH v2 02/19] fs/locks: Add Exclusive flag to user Layout lease
Date: Wed, 14 Aug 2019 10:15:06 -0400 [thread overview]
Message-ID: <fde2959db776616008fc5d31df700f5d7d899433.camel@kernel.org> (raw)
In-Reply-To: <20190809225833.6657-3-ira.weiny@intel.com>
On Fri, 2019-08-09 at 15:58 -0700, ira.weiny@intel.com wrote:
> From: Ira Weiny <ira.weiny@intel.com>
>
> Add an exclusive lease flag which indicates that the layout mechanism
> can not be broken.
>
> Exclusive layout leases allow the file system to know that pages may be
> GUP pined and that attempts to change the layout, ie truncate, should be
> failed.
>
> A process which attempts to break it's own exclusive lease gets an
> EDEADLOCK return to help determine that this is likely a programming bug
> vs someone else holding a resource.
>
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>
> ---
> fs/locks.c | 23 +++++++++++++++++++++--
> include/linux/fs.h | 1 +
> include/uapi/asm-generic/fcntl.h | 2 ++
> 3 files changed, 24 insertions(+), 2 deletions(-)
>
> diff --git a/fs/locks.c b/fs/locks.c
> index ad17c6ffca06..0c7359cdab92 100644
> --- a/fs/locks.c
> +++ b/fs/locks.c
> @@ -626,6 +626,8 @@ static int lease_init(struct file *filp, long type, unsigned int flags,
> fl->fl_flags = FL_LEASE;
> if (flags & FL_LAYOUT)
> fl->fl_flags |= FL_LAYOUT;
> + if (flags & FL_EXCLUSIVE)
> + fl->fl_flags |= FL_EXCLUSIVE;
> fl->fl_start = 0;
> fl->fl_end = OFFSET_MAX;
> fl->fl_ops = NULL;
> @@ -1619,6 +1621,14 @@ int __break_lease(struct inode *inode, unsigned int mode, unsigned int type)
> list_for_each_entry_safe(fl, tmp, &ctx->flc_lease, fl_list) {
> if (!leases_conflict(fl, new_fl))
> continue;
> + if (fl->fl_flags & FL_EXCLUSIVE) {
> + error = -ETXTBSY;
> + if (new_fl->fl_pid == fl->fl_pid) {
> + error = -EDEADLOCK;
> + goto out;
> + }
> + continue;
> + }
> if (want_write) {
> if (fl->fl_flags & FL_UNLOCK_PENDING)
> continue;
> @@ -1634,6 +1644,13 @@ int __break_lease(struct inode *inode, unsigned int mode, unsigned int type)
> locks_delete_lock_ctx(fl, &dispose);
> }
>
> + /* We differentiate between -EDEADLOCK and -ETXTBSY so the above loop
> + * continues with -ETXTBSY looking for a potential deadlock instead.
> + * If deadlock is not found go ahead and return -ETXTBSY.
> + */
> + if (error == -ETXTBSY)
> + goto out;
> +
> if (list_empty(&ctx->flc_lease))
> goto out;
>
> @@ -2044,9 +2061,11 @@ static int do_fcntl_add_lease(unsigned int fd, struct file *filp, long arg)
> * to revoke the lease in break_layout() And this is done by using
> * F_WRLCK in the break code.
> */
> - if (arg == F_LAYOUT) {
> + if ((arg & F_LAYOUT) == F_LAYOUT) {
> + if ((arg & F_EXCLUSIVE) == F_EXCLUSIVE)
> + flags |= FL_EXCLUSIVE;
> arg = F_RDLCK;
> - flags = FL_LAYOUT;
> + flags |= FL_LAYOUT;
> }
>
> fl = lease_alloc(filp, arg, flags);
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index dd60d5be9886..2e41ce547913 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1005,6 +1005,7 @@ static inline struct file *get_file(struct file *f)
> #define FL_UNLOCK_PENDING 512 /* Lease is being broken */
> #define FL_OFDLCK 1024 /* lock is "owned" by struct file */
> #define FL_LAYOUT 2048 /* outstanding pNFS layout or user held pin */
> +#define FL_EXCLUSIVE 4096 /* Layout lease is exclusive */
>
> #define FL_CLOSE_POSIX (FL_POSIX | FL_CLOSE)
>
> diff --git a/include/uapi/asm-generic/fcntl.h b/include/uapi/asm-generic/fcntl.h
> index baddd54f3031..88b175ceccbc 100644
> --- a/include/uapi/asm-generic/fcntl.h
> +++ b/include/uapi/asm-generic/fcntl.h
> @@ -176,6 +176,8 @@ struct f_owner_ex {
>
> #define F_LAYOUT 16 /* layout lease to allow longterm pins such as
> RDMA */
> +#define F_EXCLUSIVE 32 /* layout lease is exclusive */
> + /* FIXME or shoudl this be F_EXLCK??? */
>
> /* operations for bsd flock(), also used by the kernel implementation */
> #define LOCK_SH 1 /* shared lock */
This interface just seems weird to me. The existing F_*LCK values aren't
really set up to be flags, but are enumerated values (even if there are
some gaps on some arches). For instance, on parisc and sparc:
/* for posix fcntl() and lockf() */
#define F_RDLCK 01
#define F_WRLCK 02
#define F_UNLCK 03
While your new flag values are well above these values, it's still a bit
sketchy to do what you're proposing from a cross-platform interface
standpoint.
I think this would be a lot cleaner if you weren't overloading the
F_SETLEASE command with new flags, and instead added new
F_SETLAYOUT/F_GETLAYOUT cmd values.
You'd then be free to define a new set of "arg" values for use with
layouts, and there's be a clear distinction interface-wise between
setting a layout and a lease.
--
Jeff Layton <jlayton@kernel.org>
next prev parent reply other threads:[~2019-08-14 14:15 UTC|newest]
Thread overview: 110+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-09 22:58 [RFC PATCH v2 00/19] RDMA/FS DAX truncate proposal V1,000,002 ;-) ira.weiny
2019-08-09 22:58 ` [RFC PATCH v2 01/19] fs/locks: Export F_LAYOUT lease to user space ira.weiny
2019-08-09 23:52 ` Dave Chinner
2019-08-12 17:36 ` Ira Weiny
2019-08-14 8:05 ` Dave Chinner
2019-08-14 11:21 ` Jeff Layton
2019-08-14 11:38 ` Dave Chinner
2019-08-09 22:58 ` [RFC PATCH v2 02/19] fs/locks: Add Exclusive flag to user Layout lease ira.weiny
2019-08-14 14:15 ` Jeff Layton [this message]
2019-08-14 21:56 ` Dave Chinner
2019-08-26 10:41 ` Jeff Layton
2019-08-29 23:34 ` Ira Weiny
2019-09-04 12:52 ` Jeff Layton
2019-09-04 23:12 ` John Hubbard
2019-08-09 22:58 ` [RFC PATCH v2 03/19] mm/gup: Pass flags down to __gup_device_huge* calls ira.weiny
2019-08-09 22:58 ` [RFC PATCH v2 04/19] mm/gup: Ensure F_LAYOUT lease is held prior to GUP'ing pages ira.weiny
2019-08-09 22:58 ` [RFC PATCH v2 05/19] fs/ext4: Teach ext4 to break layout leases ira.weiny
2019-08-09 22:58 ` [RFC PATCH v2 06/19] fs/ext4: Teach dax_layout_busy_page() to operate on a sub-range ira.weiny
2019-08-23 15:18 ` Vivek Goyal
2019-08-29 18:52 ` Ira Weiny
2019-08-09 22:58 ` [RFC PATCH v2 07/19] fs/xfs: Teach xfs to use new dax_layout_busy_page() ira.weiny
2019-08-09 23:30 ` Dave Chinner
2019-08-12 18:05 ` Ira Weiny
2019-08-14 8:04 ` Dave Chinner
2019-08-09 22:58 ` [RFC PATCH v2 08/19] fs/xfs: Fail truncate if page lease can't be broken ira.weiny
2019-08-09 23:22 ` Dave Chinner
2019-08-12 18:08 ` Ira Weiny
2019-08-09 22:58 ` [RFC PATCH v2 09/19] mm/gup: Introduce vaddr_pin structure ira.weiny
2019-08-10 0:06 ` John Hubbard
2019-08-09 22:58 ` [RFC PATCH v2 10/19] mm/gup: Pass a NULL vaddr_pin through GUP fast ira.weiny
2019-08-10 0:06 ` John Hubbard
2019-08-09 22:58 ` [RFC PATCH v2 11/19] mm/gup: Pass follow_page_context further down the call stack ira.weiny
2019-08-10 0:18 ` John Hubbard
2019-08-12 19:01 ` Ira Weiny
2019-08-09 22:58 ` [RFC PATCH v2 12/19] mm/gup: Prep put_user_pages() to take an vaddr_pin struct ira.weiny
2019-08-10 0:30 ` John Hubbard
2019-08-12 20:46 ` Ira Weiny
2019-08-09 22:58 ` [RFC PATCH v2 13/19] {mm,file}: Add file_pins objects ira.weiny
2019-08-09 22:58 ` [RFC PATCH v2 14/19] fs/locks: Associate file pins while performing GUP ira.weiny
2019-08-09 22:58 ` [RFC PATCH v2 15/19] mm/gup: Introduce vaddr_pin_pages() ira.weiny
2019-08-10 0:09 ` John Hubbard
2019-08-12 21:00 ` Ira Weiny
2019-08-12 21:20 ` John Hubbard
2019-08-11 23:07 ` John Hubbard
2019-08-12 21:01 ` Ira Weiny
2019-08-12 12:28 ` Jason Gunthorpe
2019-08-12 21:48 ` Ira Weiny
2019-08-13 11:47 ` Jason Gunthorpe
2019-08-13 17:46 ` Ira Weiny
2019-08-13 17:56 ` John Hubbard
2019-08-09 22:58 ` [RFC PATCH v2 16/19] RDMA/uverbs: Add back pointer to system file object ira.weiny
2019-08-12 13:00 ` Jason Gunthorpe
2019-08-12 17:28 ` Ira Weiny
2019-08-12 17:56 ` Jason Gunthorpe
2019-08-12 21:15 ` Ira Weiny
2019-08-13 11:48 ` Jason Gunthorpe
2019-08-13 17:41 ` Ira Weiny
2019-08-13 18:00 ` Jason Gunthorpe
2019-08-13 20:38 ` Ira Weiny
2019-08-14 12:23 ` Jason Gunthorpe
2019-08-14 17:50 ` Ira Weiny
2019-08-14 18:15 ` Jason Gunthorpe
2019-09-04 22:25 ` Ira Weiny
2019-09-11 8:19 ` Jason Gunthorpe
2019-08-09 22:58 ` [RFC PATCH v2 17/19] RDMA/umem: Convert to vaddr_[pin|unpin]* operations ira.weiny
2019-08-09 22:58 ` [RFC PATCH v2 18/19] {mm,procfs}: Add display file_pins proc ira.weiny
2019-08-09 22:58 ` [RFC PATCH v2 19/19] mm/gup: Remove FOLL_LONGTERM DAX exclusion ira.weiny
2019-08-14 10:17 ` [RFC PATCH v2 00/19] RDMA/FS DAX truncate proposal V1,000,002 ;-) Jan Kara
2019-08-14 18:08 ` Ira Weiny
2019-08-15 13:05 ` Jan Kara
2019-08-16 19:05 ` Ira Weiny
2019-08-16 23:20 ` [RFC PATCH v2 00/19] RDMA/FS DAX truncate proposal V1,000,002 ; -) Ira Weiny
2019-08-19 6:36 ` Jan Kara
2019-08-17 2:26 ` [RFC PATCH v2 00/19] RDMA/FS DAX truncate proposal V1,000,002 ;-) Dave Chinner
2019-08-19 6:34 ` Jan Kara
2019-08-19 9:24 ` Dave Chinner
2019-08-19 12:38 ` Jason Gunthorpe
2019-08-19 21:53 ` Ira Weiny
2019-08-20 1:12 ` Dave Chinner
2019-08-20 11:55 ` Jason Gunthorpe
2019-08-21 18:02 ` Ira Weiny
2019-08-21 18:13 ` Jason Gunthorpe
2019-08-21 18:22 ` John Hubbard
2019-08-21 18:57 ` Ira Weiny
2019-08-21 19:06 ` Ira Weiny
2019-08-21 19:48 ` Jason Gunthorpe
2019-08-21 20:44 ` Ira Weiny
2019-08-21 23:49 ` Jason Gunthorpe
2019-08-23 3:23 ` Dave Chinner
2019-08-23 12:04 ` Jason Gunthorpe
2019-08-24 0:11 ` Dave Chinner
2019-08-24 5:08 ` Ira Weiny
2019-08-26 5:55 ` Dave Chinner
2019-08-29 2:02 ` Ira Weiny
2019-08-29 3:27 ` John Hubbard
2019-08-29 16:16 ` Ira Weiny
2019-09-02 22:26 ` Dave Chinner
2019-09-04 16:54 ` Ira Weiny
2019-08-25 19:39 ` Jason Gunthorpe
2019-08-24 4:49 ` Ira Weiny
2019-08-25 19:40 ` Jason Gunthorpe
2019-08-23 0:59 ` Dave Chinner
2019-08-23 17:15 ` Ira Weiny
2019-08-24 0:18 ` Dave Chinner
2019-08-20 0:05 ` John Hubbard
2019-08-20 1:20 ` Dave Chinner
2019-08-20 3:09 ` John Hubbard
2019-08-20 3:36 ` Dave Chinner
2019-08-21 18:43 ` John Hubbard
2019-08-21 19:09 ` Ira Weiny
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