unimore/kernel-hacking-2024-linux-steffo
unimore/kernel-hacking-2024-linux-steffo
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Merge branch 'flock' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/bkl

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* 'flock' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/bkl:
  locks: turn lock_flocks into a spinlock
  fasync: re-organize fasync entry insertion to allow it under a spinlock
  locks/nfsd: allocate file lock outside of spinlock
  lockd: fix nlmsvc_notify_blocked locking
  lockd: push lock_flocks down
This commit is contained in:
Linus Torvalds 2010-10-27 18:13:34 -07:00
commit 7420a8c0de
10 changed files with 116 additions and 72 deletions
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1
fs/Kconfig
View file

@ -53,7 +53,6 @@ config EXPORTFS
config FILE_LOCKING
bool "Enable POSIX file locking API" if EMBEDDED
default y
select BKL # while lockd still uses it.
help
This option enables standard file locking support, required
for filesystems like NFS and for the flock() system

70
fs/fcntl.c
View file

@ -640,7 +640,7 @@ static void fasync_free_rcu(struct rcu_head *head)
* match the state "is the filp on a fasync list".
*
*/
static int fasync_remove_entry(struct file *filp, struct fasync_struct **fapp)
int fasync_remove_entry(struct file *filp, struct fasync_struct **fapp)
{
struct fasync_struct *fa, **fp;
int result = 0;
@ -666,21 +666,28 @@ static int fasync_remove_entry(struct file *filp, struct fasync_struct **fapp)
return result;
}
/*
* Add a fasync entry. Return negative on error, positive if
* added, and zero if did nothing but change an existing one.
*
* NOTE! It is very important that the FASYNC flag always
* match the state "is the filp on a fasync list".
*/
static int fasync_add_entry(int fd, struct file *filp, struct fasync_struct **fapp)
struct fasync_struct *fasync_alloc(void)
{
struct fasync_struct *new, *fa, **fp;
int result = 0;
return kmem_cache_alloc(fasync_cache, GFP_KERNEL);
}
new = kmem_cache_alloc(fasync_cache, GFP_KERNEL);
if (!new)
return -ENOMEM;
/*
* NOTE! This can be used only for unused fasync entries:
* entries that actually got inserted on the fasync list
* need to be released by rcu - see fasync_remove_entry.
*/
void fasync_free(struct fasync_struct *new)
{
kmem_cache_free(fasync_cache, new);
}
/*
* Insert a new entry into the fasync list. Return the pointer to the
* old one if we didn't use the new one.
*/
struct fasync_struct *fasync_insert_entry(int fd, struct file *filp, struct fasync_struct **fapp, struct fasync_struct *new)
{
struct fasync_struct *fa, **fp;
spin_lock(&filp->f_lock);
spin_lock(&fasync_lock);
@ -691,8 +698,6 @@ static int fasync_add_entry(int fd, struct file *filp, struct fasync_struct **fa
spin_lock_irq(&fa->fa_lock);
fa->fa_fd = fd;
spin_unlock_irq(&fa->fa_lock);
kmem_cache_free(fasync_cache, new);
goto out;
}
@ -702,13 +707,42 @@ static int fasync_add_entry(int fd, struct file *filp, struct fasync_struct **fa
new->fa_fd = fd;
new->fa_next = *fapp;
rcu_assign_pointer(*fapp, new);
result = 1;
filp->f_flags |= FASYNC;
out:
spin_unlock(&fasync_lock);
spin_unlock(&filp->f_lock);
return result;
return fa;
}
/*
* Add a fasync entry. Return negative on error, positive if
* added, and zero if did nothing but change an existing one.
*
* NOTE! It is very important that the FASYNC flag always
* match the state "is the filp on a fasync list".
*/
static int fasync_add_entry(int fd, struct file *filp, struct fasync_struct **fapp)
{
struct fasync_struct *new;
new = fasync_alloc();
if (!new)
return -ENOMEM;
/*
* fasync_insert_entry() returns the old (update) entry if
* it existed.
*
* So free the (unused) new entry and return 0 to let the
* caller know that we didn't add any new fasync entries.
*/
if (fasync_insert_entry(fd, filp, fapp, new)) {
fasync_free(new);
return 0;
}
return 1;
}
/*

11
fs/lockd/svc.c
View file

@ -22,7 +22,6 @@
#include <linux/in.h>
#include <linux/uio.h>
#include <linux/smp.h>
#include <linux/smp_lock.h>
#include <linux/mutex.h>
#include <linux/kthread.h>
#include <linux/freezer.h>
@ -130,15 +129,6 @@ lockd(void *vrqstp)
dprintk("NFS locking service started (ver " LOCKD_VERSION ").\n");
/*
* FIXME: it would be nice if lockd didn't spend its entire life
* running under the BKL. At the very least, it would be good to
* have someone clarify what it's intended to protect here. I've
* seen some handwavy posts about posix locking needing to be
* done under the BKL, but it's far from clear.
*/
lock_kernel();
if (!nlm_timeout)
nlm_timeout = LOCKD_DFLT_TIMEO;
nlmsvc_timeout = nlm_timeout * HZ;
@ -195,7 +185,6 @@ lockd(void *vrqstp)
if (nlmsvc_ops)
nlmsvc_invalidate_all();
nlm_shutdown_hosts();
unlock_kernel();
return 0;
}

6
fs/lockd/svclock.c
View file

@ -700,14 +700,16 @@ nlmsvc_notify_blocked(struct file_lock *fl)
struct nlm_block *block;
dprintk("lockd: VFS unblock notification for block %p\n", fl);
spin_lock(&nlm_blocked_lock);
list_for_each_entry(block, &nlm_blocked, b_list) {
if (nlm_compare_locks(&block->b_call->a_args.lock.fl, fl)) {
nlmsvc_insert_block(block, 0);
nlmsvc_insert_block_locked(block, 0);
spin_unlock(&nlm_blocked_lock);
svc_wake_up(block->b_daemon);
return;
}
}
spin_unlock(&nlm_blocked_lock);
printk(KERN_WARNING "lockd: notification for unknown block!\n");
}

9
fs/lockd/svcsubs.c
View file

@ -170,6 +170,7 @@ nlm_traverse_locks(struct nlm_host *host, struct nlm_file *file,
again:
file->f_locks = 0;
lock_flocks(); /* protects i_flock list */
for (fl = inode->i_flock; fl; fl = fl->fl_next) {
if (fl->fl_lmops != &nlmsvc_lock_operations)
continue;
@ -181,6 +182,7 @@ nlm_traverse_locks(struct nlm_host *host, struct nlm_file *file,
if (match(lockhost, host)) {
struct file_lock lock = *fl;
unlock_flocks();
lock.fl_type = F_UNLCK;
lock.fl_start = 0;
lock.fl_end = OFFSET_MAX;
@ -192,6 +194,7 @@ nlm_traverse_locks(struct nlm_host *host, struct nlm_file *file,
goto again;
}
}
unlock_flocks();
return 0;
}
@ -226,10 +229,14 @@ nlm_file_inuse(struct nlm_file *file)
if (file->f_count || !list_empty(&file->f_blocks) || file->f_shares)
return 1;
lock_flocks();
for (fl = inode->i_flock; fl; fl = fl->fl_next) {
if (fl->fl_lmops == &nlmsvc_lock_operations)
if (fl->fl_lmops == &nlmsvc_lock_operations) {
unlock_flocks();
return 1;
}
}
unlock_flocks();
file->f_locks = 0;
return 0;
}

57
fs/locks.c
View file

@ -142,6 +142,7 @@ int lease_break_time = 45;
static LIST_HEAD(file_lock_list);
static LIST_HEAD(blocked_list);
static DEFINE_SPINLOCK(file_lock_lock);
/*
* Protects the two list heads above, plus the inode->i_flock list
@ -149,23 +150,24 @@ static LIST_HEAD(blocked_list);
*/
void lock_flocks(void)
{
lock_kernel();
spin_lock(&file_lock_lock);
}
EXPORT_SYMBOL_GPL(lock_flocks);
void unlock_flocks(void)
{
unlock_kernel();
spin_unlock(&file_lock_lock);
}
EXPORT_SYMBOL_GPL(unlock_flocks);
static struct kmem_cache *filelock_cache __read_mostly;
/* Allocate an empty lock structure. */
static struct file_lock *locks_alloc_lock(void)
struct file_lock *locks_alloc_lock(void)
{
return kmem_cache_alloc(filelock_cache, GFP_KERNEL);
}
EXPORT_SYMBOL_GPL(locks_alloc_lock);
void locks_release_private(struct file_lock *fl)
{
@ -1365,7 +1367,6 @@ int fcntl_getlease(struct file *filp)
int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
{
struct file_lock *fl, **before, **my_before = NULL, *lease;
struct file_lock *new_fl = NULL;
struct dentry *dentry = filp->f_path.dentry;
struct inode *inode = dentry->d_inode;
int error, rdlease_count = 0, wrlease_count = 0;
@ -1385,11 +1386,6 @@ 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;
@ -1434,7 +1430,6 @@ int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
goto out;
}
error = 0;
if (arg == F_UNLCK)
goto out;
@ -1442,15 +1437,11 @@ int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
if (!leases_enable)
goto out;
locks_copy_lock(new_fl, lease);
locks_insert_lock(before, new_fl);
*flp = new_fl;
locks_insert_lock(before, lease);
return 0;
out:
if (new_fl != NULL)
locks_free_lock(new_fl);
locks_free_lock(lease);
return error;
}
EXPORT_SYMBOL(generic_setlease);
@ -1514,26 +1505,38 @@ EXPORT_SYMBOL_GPL(vfs_setlease);
*/
int fcntl_setlease(unsigned int fd, struct file *filp, long arg)
{
struct file_lock fl, *flp = &fl;
struct file_lock *fl;
struct fasync_struct *new;
struct inode *inode = filp->f_path.dentry->d_inode;
int error;
locks_init_lock(&fl);
error = lease_init(filp, arg, &fl);
if (error)
return error;
fl = lease_alloc(filp, arg);
if (IS_ERR(fl))
return PTR_ERR(fl);
new = fasync_alloc();
if (!new) {
locks_free_lock(fl);
return -ENOMEM;
}
lock_flocks();
error = __vfs_setlease(filp, arg, &flp);
error = __vfs_setlease(filp, arg, &fl);
if (error || arg == F_UNLCK)
goto out_unlock;
error = fasync_helper(fd, filp, 1, &flp->fl_fasync);
/*
* fasync_insert_entry() returns the old entry if any.
* If there was no old entry, then it used 'new' and
* inserted it into the fasync list. Clear new so that
* we don't release it here.
*/
if (!fasync_insert_entry(fd, filp, &fl->fl_fasync, new))
new = NULL;
if (error < 0) {
/* remove lease just inserted by setlease */
flp->fl_type = F_UNLCK | F_INPROGRESS;
flp->fl_break_time = jiffies - 10;
fl->fl_type = F_UNLCK | F_INPROGRESS;
fl->fl_break_time = jiffies - 10;
time_out_leases(inode);
goto out_unlock;
}
@ -1541,6 +1544,8 @@ int fcntl_setlease(unsigned int fd, struct file *filp, long arg)
error = __f_setown(filp, task_pid(current), PIDTYPE_PID, 0);
out_unlock:
unlock_flocks();
if (new)
fasync_free(new);
return error;
}

1
fs/nfs/Kconfig
View file

@ -1,7 +1,6 @@
config NFS_FS
tristate "NFS client support"
depends on INET && FILE_LOCKING
depends on BKL # fix as soon as lockd is done
select LOCKD
select SUNRPC
select NFS_ACL_SUPPORT if NFS_V3_ACL

1
fs/nfsd/Kconfig
View file

@ -2,7 +2,6 @@ config NFSD
tristate "NFS server support"
depends on INET
depends on FILE_LOCKING
depends on BKL # fix as soon as lockd is done
select LOCKD
select SUNRPC
select EXPORTFS

26
fs/nfsd/nfs4state.c
View file

@ -2614,7 +2614,7 @@ nfs4_open_delegation(struct svc_fh *fh, struct nfsd4_open *open, struct nfs4_sta
struct nfs4_delegation *dp;
struct nfs4_stateowner *sop = stp->st_stateowner;
int cb_up = atomic_read(&sop->so_client->cl_cb_set);
struct file_lock fl, *flp = &fl;
struct file_lock *fl;
int status, flag = 0;
flag = NFS4_OPEN_DELEGATE_NONE;
@ -2648,20 +2648,24 @@ nfs4_open_delegation(struct svc_fh *fh, struct nfsd4_open *open, struct nfs4_sta
flag = NFS4_OPEN_DELEGATE_NONE;
goto out;
}
locks_init_lock(&fl);
fl.fl_lmops = &nfsd_lease_mng_ops;
fl.fl_flags = FL_LEASE;
fl.fl_type = flag == NFS4_OPEN_DELEGATE_READ? F_RDLCK: F_WRLCK;
fl.fl_end = OFFSET_MAX;
fl.fl_owner = (fl_owner_t)dp;
fl.fl_file = find_readable_file(stp->st_file);
BUG_ON(!fl.fl_file);
fl.fl_pid = current->tgid;
status = -ENOMEM;
fl = locks_alloc_lock();
if (!fl)
goto out;
locks_init_lock(fl);
fl->fl_lmops = &nfsd_lease_mng_ops;
fl->fl_flags = FL_LEASE;
fl->fl_type = flag == NFS4_OPEN_DELEGATE_READ? F_RDLCK: F_WRLCK;
fl->fl_end = OFFSET_MAX;
fl->fl_owner = (fl_owner_t)dp;
fl->fl_file = find_readable_file(stp->st_file);
BUG_ON(!fl->fl_file);
fl->fl_pid = current->tgid;
/* vfs_setlease checks to see if delegation should be handed out.
* the lock_manager callbacks fl_mylease and fl_change are used
*/
if ((status = vfs_setlease(fl.fl_file, fl.fl_type, &flp))) {
if ((status = vfs_setlease(fl->fl_file, fl->fl_type, &fl))) {
dprintk("NFSD: setlease failed [%d], no delegation\n", status);
unhash_delegation(dp);
flag = NFS4_OPEN_DELEGATE_NONE;

6
include/linux/fs.h
View file

@ -1122,6 +1122,7 @@ extern int fcntl_getlease(struct file *filp);
/* fs/locks.c */
extern void locks_init_lock(struct file_lock *);
extern struct file_lock * locks_alloc_lock(void);
extern void locks_copy_lock(struct file_lock *, struct file_lock *);
extern void __locks_copy_lock(struct file_lock *, const struct file_lock *);
extern void locks_remove_posix(struct file *, fl_owner_t);
@ -1310,6 +1311,11 @@ struct fasync_struct {
/* SMP safe fasync helpers: */
extern int fasync_helper(int, struct file *, int, struct fasync_struct **);
extern struct fasync_struct *fasync_insert_entry(int, struct file *, struct fasync_struct **, struct fasync_struct *);
extern int fasync_remove_entry(struct file *, struct fasync_struct **);
extern struct fasync_struct *fasync_alloc(void);
extern void fasync_free(struct fasync_struct *);
/* can be called from interrupts */
extern void kill_fasync(struct fasync_struct **, int, int);