Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Mon, 17 Jun 2002 12:54:13 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Mon, 17 Jun 2002 12:54:13 -0400 Received: from supreme.pcug.org.au ([203.10.76.34]:11698 "EHLO pcug.org.au") by vger.kernel.org with ESMTP id ; Mon, 17 Jun 2002 12:53:59 -0400 Date: Tue, 18 Jun 2002 02:52:54 +1000 From: Stephen Rothwell To: marcelo@conectiva.com.br Cc: linux-kernel@vger.kernel.org, matthew@wil.cx, mtk16@ext.canterbury.ac.nz Subject: Re: [PATCH] Make file leases more stable Message-Id: <20020618025254.77897157.sfr@canb.auug.org.au> In-Reply-To: <20020604103752.4e030763.sfr@canb.auug.org.au> References: <20020604103752.4e030763.sfr@canb.auug.org.au> X-Mailer: Sylpheed version 0.7.8 (GTK+ 1.2.10; i386-debian-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 11572 Lines: 420 Hi Marcelo, On Tue, 4 Jun 2002 10:37:52 +1000 Stephen Rothwell wrote: > > If you deem it appropriate, please apply this patch. > > It makes the file leases much more stable and reliable in the > presence of multiple shared leases. This patch cannot make > things worse than they currently are. :-) > > There is a further problem with leases that I am working on, but that > is harder and will require more testing. This patch supercedes the previous patch I sent you and solves the further problem I mentioned. This problem was the timing out of leases blorken by nonblocking opens. This patch has been tested and solves all the outstanding problems with file leases and makes them usable where they were not really before. It would be really good if this could make 2.4.19. -- Cheers, Stephen Rothwell sfr@canb.auug.org.au http://www.canb.auug.org.au/~sfr/ diff -ruN 2.4.19-pre10/fs/locks.c 2.4.19-pre10-leases.2/fs/locks.c --- 2.4.19-pre10/fs/locks.c Wed Oct 24 16:12:29 2001 +++ 2.4.19-pre10-leases.2/fs/locks.c Tue Jun 11 17:18:38 2002 @@ -121,6 +121,7 @@ #include #include #include +#include #include #include @@ -1051,6 +1052,47 @@ return -EINVAL; } +/* We already had a lease on this file; just change its type */ +static int lease_modify(struct file_lock **before, int arg) +{ + struct file_lock *fl = *before; + int error = assign_type(fl, arg); + + if (error) + return error; + locks_wake_up_blocks(fl, 0); + if (arg == F_UNLCK) { + struct file *filp = fl->fl_file; + + filp->f_owner.pid = 0; + filp->f_owner.uid = 0; + filp->f_owner.euid = 0; + filp->f_owner.signum = 0; + locks_delete_lock(before, 0); + } + return 0; +} + +static void time_out_leases(struct inode *inode) +{ + struct file_lock **before; + struct file_lock *fl; + + before = &inode->i_flock; + while ((fl = *before) && (fl->fl_flags & FL_LEASE) + && (fl->fl_type & F_INPROGRESS)) { + if ((fl->fl_break_time == 0) + || time_before(jiffies, fl->fl_break_time)) { + before = &fl->fl_next; + continue; + } + printk(KERN_INFO "lease broken - owner pid = %d\n", fl->fl_pid); + lease_modify(before, fl->fl_type & ~F_INPROGRESS); + if (fl == *before) /* lease_modify may have freed fl */ + before = &fl->fl_next; + } +} + /** * __get_lease - revoke all outstanding leases on file * @inode: the inode of the file to return @@ -1067,34 +1109,30 @@ struct file_lock *new_fl, *flock; struct file_lock *fl; int alloc_err; + unsigned long break_time; + int i_have_this_lease = 0; - alloc_err = lease_alloc(NULL, 0, &new_fl); + alloc_err = lease_alloc(NULL, mode & FMODE_WRITE ? F_WRLCK : F_RDLCK, + &new_fl); lock_kernel(); + + time_out_leases(inode); + flock = inode->i_flock; - if (flock->fl_type & F_INPROGRESS) { - if ((mode & O_NONBLOCK) - || (flock->fl_owner == current->files)) { - error = -EWOULDBLOCK; - goto out; - } - if (alloc_err != 0) { - error = alloc_err; - goto out; - } - do { - error = locks_block_on(flock, new_fl); - if (error != 0) - goto out; - flock = inode->i_flock; - if (!(flock && (flock->fl_flags & FL_LEASE))) - goto out; - } while (flock->fl_type & F_INPROGRESS); - } + if ((flock == NULL) || (flock->fl_flags & FL_LEASE) == 0) + goto out; + + for (fl = flock; fl && (fl->fl_flags & FL_LEASE); fl = fl->fl_next) + if (fl->fl_owner == current->files) + i_have_this_lease = 1; if (mode & FMODE_WRITE) { /* If we want write access, we have to revoke any lease. */ future = F_UNLCK | F_INPROGRESS; + } else if (flock->fl_type & F_INPROGRESS) { + /* If the lease is already being broken, we just leave it */ + future = flock->fl_type; } else if (flock->fl_type & F_WRLCK) { /* Downgrade the exclusive lease to a read-only lease. */ future = F_RDLCK | F_INPROGRESS; @@ -1103,38 +1141,49 @@ goto out; } - if (alloc_err && (flock->fl_owner != current->files)) { + if (alloc_err && !i_have_this_lease && ((mode & O_NONBLOCK) == 0)) { error = alloc_err; goto out; } - fl = flock; - do { - fl->fl_type = future; - fl = fl->fl_next; - } while (fl != NULL && (fl->fl_flags & FL_LEASE)); + break_time = 0; + if (lease_break_time > 0) { + break_time = jiffies + lease_break_time * HZ; + if (break_time == 0) + break_time++; /* so that 0 means no break time */ + } - kill_fasync(&flock->fl_fasync, SIGIO, POLL_MSG); + for (fl = flock; fl && (fl->fl_flags & FL_LEASE); fl = fl->fl_next) { + if (fl->fl_type != future) { + fl->fl_type = future; + fl->fl_break_time = break_time; + kill_fasync(&fl->fl_fasync, SIGIO, POLL_MSG); + } + } - if ((mode & O_NONBLOCK) || (flock->fl_owner == current->files)) { + if (i_have_this_lease || (mode & O_NONBLOCK)) { error = -EWOULDBLOCK; goto out; } - if (lease_break_time > 0) - error = lease_break_time * HZ; - else - error = 0; restart: - error = locks_block_on_timeout(flock, new_fl, error); - if (error == 0) { - /* We timed out. Unilaterally break the lease. */ - locks_delete_lock(&inode->i_flock, 0); - printk(KERN_WARNING "lease timed out\n"); - } else if (error > 0) { - flock = inode->i_flock; - if (flock && (flock->fl_flags & FL_LEASE)) - goto restart; + break_time = flock->fl_break_time; + if (break_time != 0) { + break_time -= jiffies; + if (break_time == 0) + break_time++; + } + error = locks_block_on_timeout(flock, new_fl, break_time); + if (error >= 0) { + if (error == 0) + time_out_leases(inode); + /* Wait for the next lease that has not been broken yet */ + for (flock = inode->i_flock; + flock && (flock->fl_flags & FL_LEASE); + flock = flock->fl_next) { + if (flock->fl_type & F_INPROGRESS) + goto restart; + } error = 0; } @@ -1166,45 +1215,41 @@ * @filp: the file * * The value returned by this function will be one of + * (if no lease break is pending): * - * %F_RDLCK to indicate a read-only (type II) lease is held. + * %F_RDLCK to indicate a shared lease is held. * * %F_WRLCK to indicate an exclusive lease is held. * - * XXX: sfr & i disagree over whether F_INPROGRESS + * %F_UNLCK to indicate no lease is held. + * + * (if a lease break is pending): + * + * %F_RDLCK to indicate an exclusive lease needs to be + * changed to a shared lease (or removed). + * + * %F_UNLCK to indicate the lease needs to be removed. + * + * XXX: sfr & willy disagree over whether F_INPROGRESS * should be returned to userspace. */ int fcntl_getlease(struct file *filp) { struct file_lock *fl; - - fl = filp->f_dentry->d_inode->i_flock; - if ((fl == NULL) || ((fl->fl_flags & FL_LEASE) == 0)) - return F_UNLCK; - return fl->fl_type & ~F_INPROGRESS; -} + int type = F_UNLCK; -/* We already had a lease on this file; just change its type */ -static int lease_modify(struct file_lock **before, int arg, int fd, struct file *filp) -{ - struct file_lock *fl = *before; - int error = assign_type(fl, arg); - if (error < 0) - goto out; - - locks_wake_up_blocks(fl, 0); - - if (arg == F_UNLCK) { - filp->f_owner.pid = 0; - filp->f_owner.uid = 0; - filp->f_owner.euid = 0; - filp->f_owner.signum = 0; - locks_delete_lock(before, 0); - fasync_helper(fd, filp, 0, &fl->fl_fasync); + lock_kernel(); + time_out_leases(filp->f_dentry->d_inode); + for (fl = filp->f_dentry->d_inode->i_flock; + fl && (fl->fl_flags & FL_LEASE); + fl = fl->fl_next) { + if (fl->fl_file == filp) { + type = fl->fl_type & ~F_INPROGRESS; + break; + } } - -out: - return error; + unlock_kernel(); + return type; } /** @@ -1232,50 +1277,59 @@ if (!S_ISREG(inode->i_mode)) return -EINVAL; + lock_kernel(); + + time_out_leases(inode); + /* * FIXME: What about F_RDLCK and files open for writing? */ + error = -EAGAIN; if ((arg == F_WRLCK) && ((atomic_read(&dentry->d_count) > 1) || (atomic_read(&inode->i_count) > 1))) - return -EAGAIN; - - before = &inode->i_flock; - - lock_kernel(); + goto out_unlock; - while ((fl = *before) != NULL) { - if (fl->fl_flags != FL_LEASE) - break; + /* + * At this point, we know that if there is an exclusive + * lease on this file, then we hold it on this filp + * (otherwise our open of this file would have blocked). + * And if we are trying to acquire an exclusive lease, + * then the file is not open by anyone (including us) + * except for this filp. + */ + for (before = &inode->i_flock; + ((fl = *before) != NULL) && (fl->fl_flags & FL_LEASE); + before = &fl->fl_next) { if (fl->fl_file == filp) my_before = before; - else if (fl->fl_type & F_WRLCK) + else if (fl->fl_type == (F_INPROGRESS | F_UNLCK)) + /* + * Someone is in the process of opening this + * file for writing so we may not take an + * exclusive lease on it. + */ wrlease_count++; else rdlease_count++; - before = &fl->fl_next; } if ((arg == F_RDLCK && (wrlease_count > 0)) || - (arg == F_WRLCK && ((rdlease_count + wrlease_count) > 0))) { - error = -EAGAIN; + (arg == F_WRLCK && ((rdlease_count + wrlease_count) > 0))) goto out_unlock; - } if (my_before != NULL) { - error = lease_modify(my_before, arg, fd, filp); + error = lease_modify(my_before, arg); goto out_unlock; } - if (arg == F_UNLCK) { - error = 0; + error = 0; + if (arg == F_UNLCK) goto out_unlock; - } - if (!leases_enable) { - error = -EINVAL; + error = -EINVAL; + if (!leases_enable) goto out_unlock; - } error = lease_alloc(filp, arg, &fl); if (error) @@ -1710,10 +1764,15 @@ before = &inode->i_flock; while ((fl = *before) != NULL) { - if ((fl->fl_flags & (FL_FLOCK|FL_LEASE)) - && (fl->fl_file == filp)) { - locks_delete_lock(before, 0); - continue; + if (fl->fl_file == filp) { + if (fl->fl_flags & FL_FLOCK) { + locks_delete_lock(before, 0); + continue; + } + if (fl->fl_flags & FL_LEASE) { + lease_modify(before, F_UNLCK); + continue; + } } before = &fl->fl_next; } @@ -1769,7 +1828,13 @@ #endif out += sprintf(out, "FLOCK ADVISORY "); } else if (fl->fl_flags & FL_LEASE) { - out += sprintf(out, "LEASE MANDATORY "); + out += sprintf(out, "LEASE "); + if (fl->fl_type & F_INPROGRESS) + out += sprintf(out, "BREAKING "); + else if (fl->fl_file) + out += sprintf(out, "ACTIVE "); + else + out += sprintf(out, "BREAKER "); } else { out += sprintf(out, "UNKNOWN UNKNOWN "); } @@ -1782,7 +1847,9 @@ } else #endif out += sprintf(out, "%s ", - (fl->fl_type & F_WRLCK) ? "WRITE" : "READ "); + (fl->fl_type & F_INPROGRESS) + ? (fl->fl_type & F_UNLCK) ? "UNLCK" : "READ " + : (fl->fl_type & F_WRLCK) ? "WRITE" : "READ "); out += sprintf(out, "%d %s:%ld ", fl->fl_pid, inode ? kdevname(inode->i_dev) : "", diff -ruN 2.4.19-pre10/include/linux/fs.h 2.4.19-pre10-leases.2/include/linux/fs.h --- 2.4.19-pre10/include/linux/fs.h Tue Jun 4 13:56:34 2002 +++ 2.4.19-pre10-leases.2/include/linux/fs.h Tue Jun 11 13:50:05 2002 @@ -595,6 +595,7 @@ void (*fl_remove)(struct file_lock *); /* lock removal callback */ struct fasync_struct * fl_fasync; /* for lease break notifications */ + unsigned long fl_break_time; /* for nonblocking lease breaks */ union { struct nfs_lock_info nfs_fl; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/