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Date: Sun, 19 Sep 2010 20:59:01 -0700 (PDT)
From: Sage Weil <sage@...dream.net>
To: Arnd Bergmann <arnd@...db.de>
cc: linux-kernel@...r.kernel.org,
Matthew Wilcox <willy@...ux.intel.com>,
Christoph Hellwig <hch@....de>,
Trond Myklebust <trond.myklebust@....uio.no>,
"J. Bruce Fields" <bfields@...ldses.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Miklos Szeredi <mszeredi@...e.cz>,
Frederic Weisbecker <fweisbec@...il.com>,
Ingo Molnar <mingo@...hat.com>, John Kacur <jkacur@...hat.com>,
linux-fsdevel@...r.kernel.org, gregf@...newdream.net
Subject: Re: [PATCH] fs/locks.c: prepare for BKL removal
Hi Arnd,
On Sat, 18 Sep 2010, Arnd Bergmann wrote:
> This prepares the removal of the big kernel lock from the
> file locking code. We still use the BKL as long as fs/lockd
> uses it and ceph might sleep, but we can flip the definition
> to a private spinlock as soon as that's done.
> All users outside of fs/lockd get converted to use
> lock_flocks() instead of lock_kernel() where appropriate.
>
> Based on an earlier patch to use a spinlock from Matthew
> Wilcox, who has attempted this a few times before. An even
> earlier attempt to use a semaphore instead of the BKL
> apparently was made by Andrew Morton about ten years ago,
> but reverted for performance reasons.
>
> Someone should do some serious performance testing when
> this becomes a spinlock, since this has caused problems
> before. Using a spinlock should be at least as good
> as the BKL in theory, but who knows...
>
> If nobody has any objections to this preparation patch,
> I'd like to add it to my bkl/vfs tree and into -next.
Is this destined for 2.6.37?
We have the Ceph preparatory patches ready. They're actually in
linux-next now, because -next also includes some ceph code reorganization,
and git isn't quite smart enough to merge the two on its own. Which makes
a bit of a mess of things... :(
I suspect the easiest thing is to leave Ceph out of this stage of your
series, I'll switch lock_kernel() to lock_flocks() once that exists
upstream. Unless there is a better way?
sage
>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> Cc: Matthew Wilcox <willy@...ux.intel.com>
> Cc: Christoph Hellwig <hch@....de>
> Cc: Trond Myklebust <trond.myklebust@....uio.no>
> Cc: "J. Bruce Fields" <bfields@...ldses.org>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Miklos Szeredi <mszeredi@...e.cz>
> Cc: Frederic Weisbecker <fweisbec@...il.com>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: John Kacur <jkacur@...hat.com>
> Cc: Sage Weil <sage@...dream.net>
> Cc: linux-kernel@...r.kernel.org
> Cc: linux-fsdevel@...r.kernel.org
> ---
> fs/afs/flock.c | 5 +-
> fs/ceph/mds_client.c | 6 +-
> fs/cifs/cifsfs.c | 4 +-
> fs/gfs2/file.c | 2 +
> fs/locks.c | 112 ++++++++++++++++++++++++++++++-------------------
> fs/nfs/delegation.c | 10 ++--
> fs/nfs/nfs4state.c | 10 ++--
> fs/nfsd/nfs4state.c | 6 +-
> include/linux/fs.h | 10 ++++
> 9 files changed, 100 insertions(+), 65 deletions(-)
>
> diff --git a/fs/afs/flock.c b/fs/afs/flock.c
> index 0931bc1..757d664 100644
> --- a/fs/afs/flock.c
> +++ b/fs/afs/flock.c
> @@ -9,7 +9,6 @@
> * 2 of the License, or (at your option) any later version.
> */
>
> -#include <linux/smp_lock.h>
> #include "internal.h"
>
> #define AFS_LOCK_GRANTED 0
> @@ -274,7 +273,7 @@ static int afs_do_setlk(struct file *file, struct file_lock *fl)
>
> type = (fl->fl_type == F_RDLCK) ? AFS_LOCK_READ : AFS_LOCK_WRITE;
>
> - lock_kernel();
> + lock_flocks();
>
> /* make sure we've got a callback on this file and that our view of the
> * data version is up to date */
> @@ -421,7 +420,7 @@ given_lock:
> afs_vnode_fetch_status(vnode, NULL, key);
>
> error:
> - unlock_kernel();
> + unlock_flocks();
> _leave(" = %d", ret);
> return ret;
>
> diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
> index f091b13..bda5211 100644
> --- a/fs/ceph/mds_client.c
> +++ b/fs/ceph/mds_client.c
> @@ -3,7 +3,7 @@
> #include <linux/wait.h>
> #include <linux/slab.h>
> #include <linux/sched.h>
> -#include <linux/smp_lock.h>
> +#include <linux/fs.h>
>
> #include "mds_client.h"
> #include "mon_client.h"
> @@ -2362,7 +2362,7 @@ static int encode_caps_cb(struct inode *inode, struct ceph_cap *cap,
> if (recon_state->flock) {
> int num_fcntl_locks, num_flock_locks;
>
> - lock_kernel();
> + lock_flocks();
> ceph_count_locks(inode, &num_fcntl_locks, &num_flock_locks);
> rec.v2.flock_len = (2*sizeof(u32) +
> (num_fcntl_locks+num_flock_locks) *
> @@ -2373,7 +2373,7 @@ static int encode_caps_cb(struct inode *inode, struct ceph_cap *cap,
> err = ceph_encode_locks(inode, pagelist,
> num_fcntl_locks,
> num_flock_locks);
> - unlock_kernel();
> + unlock_flocks();
> }
>
> out_free:
> diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
> index b7431af..b987026 100644
> --- a/fs/cifs/cifsfs.c
> +++ b/fs/cifs/cifsfs.c
> @@ -565,8 +565,8 @@ static loff_t cifs_llseek(struct file *file, loff_t offset, int origin)
>
> static int cifs_setlease(struct file *file, long arg, struct file_lock **lease)
> {
> - /* note that this is called by vfs setlease with the BKL held
> - although I doubt that BKL is needed here in cifs */
> + /* note that this is called by vfs setlease with lock_flocks held
> + to protect *lease from going away */
> struct inode *inode = file->f_path.dentry->d_inode;
>
> if (!(S_ISREG(inode->i_mode)))
> diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c
> index 4edd662..8fcfefb 100644
> --- a/fs/gfs2/file.c
> +++ b/fs/gfs2/file.c
> @@ -620,6 +620,8 @@ static ssize_t gfs2_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
> * cluster; until we do, disable leases (by just returning -EINVAL),
> * unless the administrator has requested purely local locking.
> *
> + * Locking: called under lock_flocks
> + *
> * Returns: errno
> */
>
> diff --git a/fs/locks.c b/fs/locks.c
> index ab24d49..8b2b6ad 100644
> --- a/fs/locks.c
> +++ b/fs/locks.c
> @@ -143,6 +143,22 @@ int lease_break_time = 45;
> static LIST_HEAD(file_lock_list);
> static LIST_HEAD(blocked_list);
>
> +/*
> + * Protects the two list heads above, plus the inode->i_flock list
> + * FIXME: should use a spinlock, once lockd and ceph are ready.
> + */
> +void lock_flocks(void)
> +{
> + lock_kernel();
> +}
> +EXPORT_SYMBOL_GPL(lock_flocks);
> +
> +void unlock_flocks(void)
> +{
> + unlock_kernel();
> +}
> +EXPORT_SYMBOL_GPL(unlock_flocks);
> +
> static struct kmem_cache *filelock_cache __read_mostly;
>
> /* Allocate an empty lock structure. */
> @@ -511,9 +527,9 @@ static void __locks_delete_block(struct file_lock *waiter)
> */
> static void locks_delete_block(struct file_lock *waiter)
> {
> - lock_kernel();
> + lock_flocks();
> __locks_delete_block(waiter);
> - unlock_kernel();
> + unlock_flocks();
> }
>
> /* Insert waiter into blocker's block list.
> @@ -644,7 +660,7 @@ posix_test_lock(struct file *filp, struct file_lock *fl)
> {
> struct file_lock *cfl;
>
> - lock_kernel();
> + lock_flocks();
> for (cfl = filp->f_path.dentry->d_inode->i_flock; cfl; cfl = cfl->fl_next) {
> if (!IS_POSIX(cfl))
> continue;
> @@ -657,7 +673,7 @@ posix_test_lock(struct file *filp, struct file_lock *fl)
> fl->fl_pid = pid_vnr(cfl->fl_nspid);
> } else
> fl->fl_type = F_UNLCK;
> - unlock_kernel();
> + unlock_flocks();
> return;
> }
> EXPORT_SYMBOL(posix_test_lock);
> @@ -730,18 +746,16 @@ static int flock_lock_file(struct file *filp, struct file_lock *request)
> int error = 0;
> int found = 0;
>
> - lock_kernel();
> - if (request->fl_flags & FL_ACCESS)
> - goto find_conflict;
> -
> - if (request->fl_type != F_UNLCK) {
> - error = -ENOMEM;
> + if (!(request->fl_flags & FL_ACCESS) && (request->fl_type != F_UNLCK)) {
> new_fl = locks_alloc_lock();
> - if (new_fl == NULL)
> - goto out;
> - error = 0;
> + if (!new_fl)
> + return -ENOMEM;
> }
>
> + lock_flocks();
> + if (request->fl_flags & FL_ACCESS)
> + goto find_conflict;
> +
> for_each_lock(inode, before) {
> struct file_lock *fl = *before;
> if (IS_POSIX(fl))
> @@ -767,8 +781,11 @@ static int flock_lock_file(struct file *filp, struct file_lock *request)
> * If a higher-priority process was blocked on the old file lock,
> * give it the opportunity to lock the file.
> */
> - if (found)
> + if (found) {
> + unlock_flocks();
> cond_resched();
> + lock_flocks();
> + }
>
> find_conflict:
> for_each_lock(inode, before) {
> @@ -794,7 +811,7 @@ find_conflict:
> error = 0;
>
> out:
> - unlock_kernel();
> + unlock_flocks();
> if (new_fl)
> locks_free_lock(new_fl);
> return error;
> @@ -823,7 +840,7 @@ static int __posix_lock_file(struct inode *inode, struct file_lock *request, str
> new_fl2 = locks_alloc_lock();
> }
>
> - lock_kernel();
> + lock_flocks();
> if (request->fl_type != F_UNLCK) {
> for_each_lock(inode, before) {
> fl = *before;
> @@ -991,7 +1008,7 @@ static int __posix_lock_file(struct inode *inode, struct file_lock *request, str
> locks_wake_up_blocks(left);
> }
> out:
> - unlock_kernel();
> + unlock_flocks();
> /*
> * Free any unused locks.
> */
> @@ -1066,14 +1083,14 @@ int locks_mandatory_locked(struct inode *inode)
> /*
> * Search the lock list for this inode for any POSIX locks.
> */
> - lock_kernel();
> + lock_flocks();
> for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
> if (!IS_POSIX(fl))
> continue;
> if (fl->fl_owner != owner)
> break;
> }
> - unlock_kernel();
> + unlock_flocks();
> return fl ? -EAGAIN : 0;
> }
>
> @@ -1186,7 +1203,7 @@ int __break_lease(struct inode *inode, unsigned int mode)
>
> new_fl = lease_alloc(NULL, want_write ? F_WRLCK : F_RDLCK);
>
> - lock_kernel();
> + lock_flocks();
>
> time_out_leases(inode);
>
> @@ -1247,8 +1264,10 @@ restart:
> break_time++;
> }
> locks_insert_block(flock, new_fl);
> + unlock_flocks();
> error = wait_event_interruptible_timeout(new_fl->fl_wait,
> !new_fl->fl_next, break_time);
> + lock_flocks();
> __locks_delete_block(new_fl);
> if (error >= 0) {
> if (error == 0)
> @@ -1263,7 +1282,7 @@ restart:
> }
>
> out:
> - unlock_kernel();
> + unlock_flocks();
> if (!IS_ERR(new_fl))
> locks_free_lock(new_fl);
> return error;
> @@ -1319,7 +1338,7 @@ int fcntl_getlease(struct file *filp)
> struct file_lock *fl;
> int type = F_UNLCK;
>
> - lock_kernel();
> + lock_flocks();
> time_out_leases(filp->f_path.dentry->d_inode);
> for (fl = filp->f_path.dentry->d_inode->i_flock; fl && IS_LEASE(fl);
> fl = fl->fl_next) {
> @@ -1328,7 +1347,7 @@ int fcntl_getlease(struct file *filp)
> break;
> }
> }
> - unlock_kernel();
> + unlock_flocks();
> return type;
> }
>
> @@ -1341,7 +1360,7 @@ int fcntl_getlease(struct file *filp)
> * The (input) flp->fl_lmops->fl_break function is required
> * by break_lease().
> *
> - * Called with kernel lock held.
> + * Called with file_lock_lock held.
> */
> int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
> {
> @@ -1436,7 +1455,15 @@ out:
> }
> EXPORT_SYMBOL(generic_setlease);
>
> - /**
> +static int __vfs_setlease(struct file *filp, long arg, struct file_lock **lease)
> +{
> + if (filp->f_op && filp->f_op->setlease)
> + return filp->f_op->setlease(filp, arg, lease);
> + else
> + return generic_setlease(filp, arg, lease);
> +}
> +
> +/**
> * vfs_setlease - sets a lease on an open file
> * @filp: file pointer
> * @arg: type of lease to obtain
> @@ -1467,12 +1494,9 @@ int vfs_setlease(struct file *filp, long arg, struct file_lock **lease)
> {
> int error;
>
> - lock_kernel();
> - if (filp->f_op && filp->f_op->setlease)
> - error = filp->f_op->setlease(filp, arg, lease);
> - else
> - error = generic_setlease(filp, arg, lease);
> - unlock_kernel();
> + lock_flocks();
> + error = __vfs_setlease(filp, arg, lease);
> + unlock_flocks();
>
> return error;
> }
> @@ -1499,9 +1523,9 @@ int fcntl_setlease(unsigned int fd, struct file *filp, long arg)
> if (error)
> return error;
>
> - lock_kernel();
> + lock_flocks();
>
> - error = vfs_setlease(filp, arg, &flp);
> + error = __vfs_setlease(filp, arg, &flp);
> if (error || arg == F_UNLCK)
> goto out_unlock;
>
> @@ -1516,7 +1540,7 @@ int fcntl_setlease(unsigned int fd, struct file *filp, long arg)
>
> error = __f_setown(filp, task_pid(current), PIDTYPE_PID, 0);
> out_unlock:
> - unlock_kernel();
> + unlock_flocks();
> return error;
> }
>
> @@ -2020,7 +2044,7 @@ void locks_remove_flock(struct file *filp)
> fl.fl_ops->fl_release_private(&fl);
> }
>
> - lock_kernel();
> + lock_flocks();
> before = &inode->i_flock;
>
> while ((fl = *before) != NULL) {
> @@ -2038,7 +2062,7 @@ void locks_remove_flock(struct file *filp)
> }
> before = &fl->fl_next;
> }
> - unlock_kernel();
> + unlock_flocks();
> }
>
> /**
> @@ -2053,12 +2077,12 @@ posix_unblock_lock(struct file *filp, struct file_lock *waiter)
> {
> int status = 0;
>
> - lock_kernel();
> + lock_flocks();
> if (waiter->fl_next)
> __locks_delete_block(waiter);
> else
> status = -ENOENT;
> - unlock_kernel();
> + unlock_flocks();
> return status;
> }
>
> @@ -2172,7 +2196,7 @@ static int locks_show(struct seq_file *f, void *v)
>
> static void *locks_start(struct seq_file *f, loff_t *pos)
> {
> - lock_kernel();
> + lock_flocks();
> f->private = (void *)1;
> return seq_list_start(&file_lock_list, *pos);
> }
> @@ -2184,7 +2208,7 @@ static void *locks_next(struct seq_file *f, void *v, loff_t *pos)
>
> static void locks_stop(struct seq_file *f, void *v)
> {
> - unlock_kernel();
> + unlock_flocks();
> }
>
> static const struct seq_operations locks_seq_operations = {
> @@ -2231,7 +2255,7 @@ int lock_may_read(struct inode *inode, loff_t start, unsigned long len)
> {
> struct file_lock *fl;
> int result = 1;
> - lock_kernel();
> + lock_flocks();
> for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
> if (IS_POSIX(fl)) {
> if (fl->fl_type == F_RDLCK)
> @@ -2248,7 +2272,7 @@ int lock_may_read(struct inode *inode, loff_t start, unsigned long len)
> result = 0;
> break;
> }
> - unlock_kernel();
> + unlock_flocks();
> return result;
> }
>
> @@ -2271,7 +2295,7 @@ int lock_may_write(struct inode *inode, loff_t start, unsigned long len)
> {
> struct file_lock *fl;
> int result = 1;
> - lock_kernel();
> + lock_flocks();
> for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
> if (IS_POSIX(fl)) {
> if ((fl->fl_end < start) || (fl->fl_start > (start + len)))
> @@ -2286,7 +2310,7 @@ int lock_may_write(struct inode *inode, loff_t start, unsigned long len)
> result = 0;
> break;
> }
> - unlock_kernel();
> + unlock_flocks();
> return result;
> }
>
> diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c
> index b9c3c43..232a7ee 100644
> --- a/fs/nfs/delegation.c
> +++ b/fs/nfs/delegation.c
> @@ -71,20 +71,20 @@ static int nfs_delegation_claim_locks(struct nfs_open_context *ctx, struct nfs4_
> if (inode->i_flock == NULL)
> goto out;
>
> - /* Protect inode->i_flock using the BKL */
> - lock_kernel();
> + /* Protect inode->i_flock using the file locks lock */
> + lock_flocks();
> for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
> if (!(fl->fl_flags & (FL_POSIX|FL_FLOCK)))
> continue;
> if (nfs_file_open_context(fl->fl_file) != ctx)
> continue;
> - unlock_kernel();
> + unlock_flocks();
> status = nfs4_lock_delegation_recall(state, fl);
> if (status < 0)
> goto out;
> - lock_kernel();
> + lock_flocks();
> }
> - unlock_kernel();
> + unlock_flocks();
> out:
> return status;
> }
> diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
> index 3e2f19b..96524c5 100644
> --- a/fs/nfs/nfs4state.c
> +++ b/fs/nfs/nfs4state.c
> @@ -40,7 +40,7 @@
>
> #include <linux/kernel.h>
> #include <linux/slab.h>
> -#include <linux/smp_lock.h>
> +#include <linux/fs.h>
> #include <linux/nfs_fs.h>
> #include <linux/nfs_idmap.h>
> #include <linux/kthread.h>
> @@ -970,13 +970,13 @@ static int nfs4_reclaim_locks(struct nfs4_state *state, const struct nfs4_state_
> /* Guard against delegation returns and new lock/unlock calls */
> down_write(&nfsi->rwsem);
> /* Protect inode->i_flock using the BKL */
> - lock_kernel();
> + lock_flocks();
> for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
> if (!(fl->fl_flags & (FL_POSIX|FL_FLOCK)))
> continue;
> if (nfs_file_open_context(fl->fl_file)->state != state)
> continue;
> - unlock_kernel();
> + unlock_flocks();
> status = ops->recover_lock(state, fl);
> switch (status) {
> case 0:
> @@ -1003,9 +1003,9 @@ static int nfs4_reclaim_locks(struct nfs4_state *state, const struct nfs4_state_
> /* kill_proc(fl->fl_pid, SIGLOST, 1); */
> status = 0;
> }
> - lock_kernel();
> + lock_flocks();
> }
> - unlock_kernel();
> + unlock_flocks();
> out:
> up_write(&nfsi->rwsem);
> return status;
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index cf0d2ff..a7292fc 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -33,7 +33,7 @@
> */
>
> #include <linux/file.h>
> -#include <linux/smp_lock.h>
> +#include <linux/fs.h>
> #include <linux/slab.h>
> #include <linux/namei.h>
> #include <linux/swap.h>
> @@ -3895,7 +3895,7 @@ check_for_locks(struct nfs4_file *filp, struct nfs4_stateowner *lowner)
> struct inode *inode = filp->fi_inode;
> int status = 0;
>
> - lock_kernel();
> + lock_flocks();
> for (flpp = &inode->i_flock; *flpp != NULL; flpp = &(*flpp)->fl_next) {
> if ((*flpp)->fl_owner == (fl_owner_t)lowner) {
> status = 1;
> @@ -3903,7 +3903,7 @@ check_for_locks(struct nfs4_file *filp, struct nfs4_stateowner *lowner)
> }
> }
> out:
> - unlock_kernel();
> + unlock_flocks();
> return status;
> }
>
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 76041b6..8970123 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1131,6 +1131,8 @@ extern int vfs_setlease(struct file *, long, struct file_lock **);
> extern int lease_modify(struct file_lock **, int);
> extern int lock_may_read(struct inode *, loff_t start, unsigned long count);
> extern int lock_may_write(struct inode *, loff_t start, unsigned long count);
> +extern void lock_flocks(void);
> +extern void unlock_flocks(void);
> #else /* !CONFIG_FILE_LOCKING */
> static inline int fcntl_getlk(struct file *file, struct flock __user *user)
> {
> @@ -1273,6 +1275,14 @@ static inline int lock_may_write(struct inode *inode, loff_t start,
> return 1;
> }
>
> +static inline void lock_flocks()
> +{
> +}
> +
> +static inline void unlock_flocks()
> +{
> +}
> +
> #endif /* !CONFIG_FILE_LOCKING */
>
>
> --
> 1.7.1
>
> --
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>
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