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SubjectRe: [PATCH] Remove BKL from fs/locks.c
Hi Arnd,

On Wed, 15 Sep 2010, Arnd Bergmann wrote:

> On Tuesday 14 September 2010, Trond Myklebust wrote:
> > Would it be possible to at least merge a patch that defines
> > lock_flocks() (even if it just is an alias for lock_kernel()), so that
> > we can convert those bits of the lock recovery code that need to peek
> > into the inode->i_flock list ASAP?
>
> Fine with me.

That's my preference. See below:

>
> Another alternative would be to keep a series of all these patches
> together, like
>
> 1. fs/locks.c: prepare for BKL removal
> 2. fs/lockd: use lock/flocks
> 3. fs/locks.c: lock_flocks using spinlock (trivial)
>
> Feel free to take the patch below into a tree of yours when
> adding patches 2 and 3 on top, or send me that patch once
> it's done and I'll add both into my tree.
>
> Linus, Christoph: Does the patch below look ok? I've removed
> the CONFIG_BKL stuff in it now and changed over everything
> besides lockd to use lock_flocks(). I'd like to put this into
> the -next queue (after some basic testing).
> ---
> Subject: [PATCH] fs/locks.c: prepare for BKL removal
>
> 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, but 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 from Matthew Wilcox.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> Cc: Matthew Wilcox <willy@linux.intel.com>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
> Cc: "J. Bruce Fields" <bfields@fieldses.org>
> Cc: Miklos Szeredi <mszeredi@suse.cz>
> Cc: Frederic Weisbecker <fweisbec@gmail.com>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: John Kacur <jkacur@redhat.com>
> Cc: linux-kernel@vger.kernel.org
> Cc: linux-fsdevel@vger.kernel.org
> ---
>
> fs/afs/flock.c | 5 +-
> fs/ceph/mds_client.c | 6 +-
> fs/locks.c | 118 ++++++++++++++++++++++++++++---------------------
> fs/nfs/delegation.c | 10 ++--
> fs/nfs/nfs4state.c | 10 ++--
> fs/nfsd/nfs4state.c | 6 +-
> include/linux/fs.h | 10 ++++
> 7 files changed, 95 insertions(+), 70 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();
> }

The Ceph code won't currently behave with lock_flocks() taking a spinlock.
We're preparing a patch to fix that now. As long as there is a window
between lock_flocks() being defined and the spinlock conversion, I can
send the fix upstream then and avoid any breakage. Or send the patches
your way to include in your tree, whatever you prefer!

>
> out_free:
> diff --git a/fs/locks.c b/fs/locks.c
> index ab24d49..8c6935f 100644
> --- a/fs/locks.c
> +++ b/fs/locks.c
> @@ -143,6 +143,21 @@ 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 fs/lockd uses lock_flocks().
> + */
> +void lock_flocks(void)
> +{
> + lock_kernel();
> +}
> +EXPORT_SYMBOL(lock_flocks);
> +
> +void unlock_flocks(void)
> +{
> + unlock_kernel();
> +}

EXPORT_SYMBOL(unlock_flocks); ?

Thanks!
sage


> +
> static struct kmem_cache *filelock_cache __read_mostly;
>
> /* Allocate an empty lock structure. */
> @@ -511,9 +526,9 @@ 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 +659,7 @@ 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 +672,7 @@ 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 +745,16 @@ 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 +780,11 @@ 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 +810,7 @@ find_conflict:
> error = 0;
>
> out:
> - unlock_kernel();
> + unlock_flocks();
> if (new_fl)
> locks_free_lock(new_fl);
> return error;
> @@ -823,7 +839,7 @@ 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 +1007,7 @@ 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 +1082,14 @@ 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 +1202,7 @@ 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 +1263,10 @@ 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 +1281,7 @@ restart:
> }
>
> out:
> - unlock_kernel();
> + unlock_flocks();
> if (!IS_ERR(new_fl))
> locks_free_lock(new_fl);
> return error;
> @@ -1319,7 +1337,7 @@ 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 +1346,7 @@ int fcntl_getlease(struct file *filp)
> break;
> }
> }
> - unlock_kernel();
> + unlock_flocks();
> return type;
> }
>
> @@ -1341,7 +1359,7 @@ 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)
> {
> @@ -1359,6 +1377,13 @@ int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
> if (error)
> return error;
>
> + if (arg != F_UNLCK) {
> + new_fl = locks_alloc_lock();
> + if (new_fl == NULL)
> + return -ENOMEM;
> + }
> +
> + lock_flocks();
> time_out_leases(inode);
>
> BUG_ON(!(*flp)->fl_lmops->fl_break);
> @@ -1366,11 +1391,6 @@ int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
> lease = *flp;
>
> if (arg != F_UNLCK) {
> - error = -ENOMEM;
> - new_fl = locks_alloc_lock();
> - if (new_fl == NULL)
> - goto out;
> -
> error = -EAGAIN;
> if ((arg == F_RDLCK) && (atomic_read(&inode->i_writecount) > 0))
> goto out;
> @@ -1427,16 +1447,18 @@ int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
> locks_insert_lock(before, new_fl);
>
> *flp = new_fl;
> + unlock_flocks();
> return 0;
>
> out:
> if (new_fl != NULL)
> locks_free_lock(new_fl);
> + unlock_flocks();
> return error;
> }
> EXPORT_SYMBOL(generic_setlease);
>
> - /**
> +/**
> * vfs_setlease - sets a lease on an open file
> * @filp: file pointer
> * @arg: type of lease to obtain
> @@ -1465,16 +1487,10 @@ EXPORT_SYMBOL(generic_setlease);
>
> 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);
> + return filp->f_op->setlease(filp, arg, lease);
> else
> - error = generic_setlease(filp, arg, lease);
> - unlock_kernel();
> -
> - return error;
> + return generic_setlease(filp, arg, lease);
> }
> EXPORT_SYMBOL_GPL(vfs_setlease);
>
> @@ -1499,12 +1515,12 @@ int fcntl_setlease(unsigned int fd, struct file *filp, long arg)
> if (error)
> return error;
>
> - lock_kernel();
> -
> error = vfs_setlease(filp, arg, &flp);
> if (error || arg == F_UNLCK)
> goto out_unlock;
>
> + lock_flocks();
> +
> error = fasync_helper(fd, filp, 1, &flp->fl_fasync);
> if (error < 0) {
> /* remove lease just inserted by setlease */
> @@ -1516,7 +1532,7 @@ 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 +2036,7 @@ 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 +2054,7 @@ void locks_remove_flock(struct file *filp)
> }
> before = &fl->fl_next;
> }
> - unlock_kernel();
> + unlock_flocks();
> }
>
> /**
> @@ -2053,12 +2069,12 @@ 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 +2188,7 @@ 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 +2200,7 @@ 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 +2247,7 @@ 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 +2264,7 @@ int lock_may_read(struct inode *inode, loff_t start, unsigned long len)
> result = 0;
> break;
> }
> - unlock_kernel();
> + unlock_flocks();
> return result;
> }
>
> @@ -2271,7 +2287,7 @@ 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 +2302,7 @@ 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 0ec4d60..fd85cd2 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1127,6 +1127,8 @@ 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)
> {
> @@ -1269,6 +1271,14 @@ 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 */
>
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
>


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