locks: fix tracking of inprogress lease breaks
We currently use a bit in fl_flags to record whether a lease is being broken, and set fl_type to the type (RDLCK or UNLCK) that it will eventually have. This means that once the lease break starts, we forget what the lease's type *used* to be. Breaking a read lease will then result in blocking read opens, even though there's no conflict--because the lease type is now F_UNLCK and we can no longer tell whether it was previously a read or write lease. So, instead keep fl_type as the original type (the type which we enforce), and keep track of whether we're unlocking or merely downgrading by replacing the single FL_INPROGRESS flag by FL_UNLOCK_PENDING and FL_DOWNGRADE_PENDING flags. To get this right we also need to track separate downgrade and break times, to handle the case where a write-leased file gets conflicting opens first for read, then later for write. (I first considered just eliminating the downgrade behavior completely--nfsv4 doesn't need it, and nobody as far as I can tell actually uses it currently--but Jeremy Allison tells me that Windows oplocks do behave this way, so Samba will probably use this some day.) Reviewed-by: Jeff Layton <jlayton@redhat.com> Signed-off-by: J. Bruce Fields <bfields@redhat.com>
This commit is contained in:
parent
710b721696
commit
778fc546f7
87
fs/locks.c
87
fs/locks.c
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@ -135,7 +135,16 @@
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static bool lease_breaking(struct file_lock *fl)
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static bool lease_breaking(struct file_lock *fl)
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{
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{
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return fl->fl_flags & FL_INPROGRESS;
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return fl->fl_flags & (FL_UNLOCK_PENDING | FL_DOWNGRADE_PENDING);
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}
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static int target_leasetype(struct file_lock *fl)
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{
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if (fl->fl_flags & FL_UNLOCK_PENDING)
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return F_UNLCK;
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if (fl->fl_flags & FL_DOWNGRADE_PENDING)
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return F_RDLCK;
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return fl->fl_type;
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}
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}
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int leases_enable = 1;
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int leases_enable = 1;
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@ -1124,6 +1133,17 @@ int locks_mandatory_area(int read_write, struct inode *inode,
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EXPORT_SYMBOL(locks_mandatory_area);
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EXPORT_SYMBOL(locks_mandatory_area);
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static void lease_clear_pending(struct file_lock *fl, int arg)
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{
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switch (arg) {
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case F_UNLCK:
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fl->fl_flags &= ~FL_UNLOCK_PENDING;
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/* fall through: */
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case F_RDLCK:
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fl->fl_flags &= ~FL_DOWNGRADE_PENDING;
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}
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}
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/* We already had a lease on this file; just change its type */
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/* We already had a lease on this file; just change its type */
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int lease_modify(struct file_lock **before, int arg)
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int lease_modify(struct file_lock **before, int arg)
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{
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{
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@ -1132,7 +1152,7 @@ int lease_modify(struct file_lock **before, int arg)
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if (error)
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if (error)
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return error;
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return error;
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fl->fl_flags &= ~FL_INPROGRESS;
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lease_clear_pending(fl, arg);
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locks_wake_up_blocks(fl);
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locks_wake_up_blocks(fl);
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if (arg == F_UNLCK)
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if (arg == F_UNLCK)
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locks_delete_lock(before);
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locks_delete_lock(before);
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@ -1141,6 +1161,14 @@ int lease_modify(struct file_lock **before, int arg)
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EXPORT_SYMBOL(lease_modify);
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EXPORT_SYMBOL(lease_modify);
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static bool past_time(unsigned long then)
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{
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if (!then)
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/* 0 is a special value meaning "this never expires": */
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return false;
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return time_after(jiffies, then);
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}
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static void time_out_leases(struct inode *inode)
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static void time_out_leases(struct inode *inode)
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{
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{
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struct file_lock **before;
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struct file_lock **before;
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@ -1148,12 +1176,10 @@ static void time_out_leases(struct inode *inode)
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before = &inode->i_flock;
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before = &inode->i_flock;
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while ((fl = *before) && IS_LEASE(fl) && lease_breaking(fl)) {
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while ((fl = *before) && IS_LEASE(fl) && lease_breaking(fl)) {
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if ((fl->fl_break_time == 0)
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if (past_time(fl->fl_downgrade_time))
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|| time_before(jiffies, fl->fl_break_time)) {
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lease_modify(before, F_RDLCK);
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before = &fl->fl_next;
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if (past_time(fl->fl_break_time))
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continue;
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lease_modify(before, F_UNLCK);
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}
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lease_modify(before, fl->fl_type);
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if (fl == *before) /* lease_modify may have freed fl */
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if (fl == *before) /* lease_modify may have freed fl */
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before = &fl->fl_next;
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before = &fl->fl_next;
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}
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}
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@ -1171,7 +1197,7 @@ static void time_out_leases(struct inode *inode)
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*/
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*/
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int __break_lease(struct inode *inode, unsigned int mode)
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int __break_lease(struct inode *inode, unsigned int mode)
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{
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{
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int error = 0, future;
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int error = 0;
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struct file_lock *new_fl, *flock;
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struct file_lock *new_fl, *flock;
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struct file_lock *fl;
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struct file_lock *fl;
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unsigned long break_time;
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unsigned long break_time;
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@ -1188,24 +1214,13 @@ int __break_lease(struct inode *inode, unsigned int mode)
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if ((flock == NULL) || !IS_LEASE(flock))
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if ((flock == NULL) || !IS_LEASE(flock))
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goto out;
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goto out;
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if (!locks_conflict(flock, new_fl))
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goto out;
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for (fl = flock; fl && IS_LEASE(fl); fl = fl->fl_next)
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for (fl = flock; fl && IS_LEASE(fl); fl = fl->fl_next)
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if (fl->fl_owner == current->files)
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if (fl->fl_owner == current->files)
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i_have_this_lease = 1;
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i_have_this_lease = 1;
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if (want_write) {
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/* If we want write access, we have to revoke any lease. */
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future = F_UNLCK;
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} else if (lease_breaking(flock)) {
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/* If the lease is already being broken, we just leave it */
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future = flock->fl_type;
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} else if (flock->fl_type & F_WRLCK) {
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/* Downgrade the exclusive lease to a read-only lease. */
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future = F_RDLCK;
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} else {
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/* the existing lease was read-only, so we can read too. */
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goto out;
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}
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if (IS_ERR(new_fl) && !i_have_this_lease
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if (IS_ERR(new_fl) && !i_have_this_lease
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&& ((mode & O_NONBLOCK) == 0)) {
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&& ((mode & O_NONBLOCK) == 0)) {
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error = PTR_ERR(new_fl);
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error = PTR_ERR(new_fl);
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@ -1220,13 +1235,18 @@ int __break_lease(struct inode *inode, unsigned int mode)
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}
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}
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for (fl = flock; fl && IS_LEASE(fl); fl = fl->fl_next) {
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for (fl = flock; fl && IS_LEASE(fl); fl = fl->fl_next) {
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if (fl->fl_type != future) {
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if (want_write) {
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fl->fl_type = future;
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if (fl->fl_flags & FL_UNLOCK_PENDING)
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fl->fl_flags |= FL_INPROGRESS;
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continue;
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fl->fl_flags |= FL_UNLOCK_PENDING;
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fl->fl_break_time = break_time;
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fl->fl_break_time = break_time;
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/* lease must have lmops break callback */
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} else {
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fl->fl_lmops->lm_break(fl);
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if (lease_breaking(flock))
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continue;
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fl->fl_flags |= FL_DOWNGRADE_PENDING;
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fl->fl_downgrade_time = break_time;
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}
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}
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fl->fl_lmops->lm_break(fl);
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}
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}
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if (i_have_this_lease || (mode & O_NONBLOCK)) {
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if (i_have_this_lease || (mode & O_NONBLOCK)) {
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@ -1250,10 +1270,13 @@ restart:
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if (error >= 0) {
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if (error >= 0) {
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if (error == 0)
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if (error == 0)
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time_out_leases(inode);
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time_out_leases(inode);
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/* Wait for the next lease that has not been broken yet */
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/*
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* Wait for the next conflicting lease that has not been
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* broken yet
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*/
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for (flock = inode->i_flock; flock && IS_LEASE(flock);
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for (flock = inode->i_flock; flock && IS_LEASE(flock);
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flock = flock->fl_next) {
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flock = flock->fl_next) {
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if (lease_breaking(flock))
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if (locks_conflict(new_fl, flock))
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goto restart;
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goto restart;
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}
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}
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error = 0;
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error = 0;
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@ -1321,7 +1344,7 @@ int fcntl_getlease(struct file *filp)
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for (fl = filp->f_path.dentry->d_inode->i_flock; fl && IS_LEASE(fl);
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for (fl = filp->f_path.dentry->d_inode->i_flock; fl && IS_LEASE(fl);
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fl = fl->fl_next) {
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fl = fl->fl_next) {
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if (fl->fl_file == filp) {
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if (fl->fl_file == filp) {
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type = fl->fl_type;
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type = target_leasetype(fl);
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break;
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break;
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}
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}
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}
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}
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@ -1386,7 +1409,7 @@ int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
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before = &fl->fl_next) {
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before = &fl->fl_next) {
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if (fl->fl_file == filp)
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if (fl->fl_file == filp)
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my_before = before;
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my_before = before;
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else if ((fl->fl_type == F_UNLCK) && lease_breaking(fl))
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else if (fl->fl_flags & FL_UNLOCK_PENDING)
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/*
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/*
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* Someone is in the process of opening this
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* Someone is in the process of opening this
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* file for writing so we may not take an
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* file for writing so we may not take an
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@ -1065,7 +1065,8 @@ static inline int file_check_writeable(struct file *filp)
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#define FL_LEASE 32 /* lease held on this file */
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#define FL_LEASE 32 /* lease held on this file */
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#define FL_CLOSE 64 /* unlock on close */
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#define FL_CLOSE 64 /* unlock on close */
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#define FL_SLEEP 128 /* A blocking lock */
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#define FL_SLEEP 128 /* A blocking lock */
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#define FL_INPROGRESS 256 /* Lease is being broken */
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#define FL_DOWNGRADE_PENDING 256 /* Lease is being downgraded */
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#define FL_UNLOCK_PENDING 512 /* Lease is being broken */
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/*
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/*
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* Special return value from posix_lock_file() and vfs_lock_file() for
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* Special return value from posix_lock_file() and vfs_lock_file() for
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@ -1122,7 +1123,9 @@ struct file_lock {
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loff_t fl_end;
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loff_t fl_end;
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struct fasync_struct * fl_fasync; /* for lease break notifications */
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struct fasync_struct * fl_fasync; /* for lease break notifications */
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unsigned long fl_break_time; /* for nonblocking lease breaks */
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/* for lease breaks: */
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unsigned long fl_break_time;
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unsigned long fl_downgrade_time;
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const struct file_lock_operations *fl_ops; /* Callbacks for filesystems */
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const struct file_lock_operations *fl_ops; /* Callbacks for filesystems */
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const struct lock_manager_operations *fl_lmops; /* Callbacks for lockmanagers */
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const struct lock_manager_operations *fl_lmops; /* Callbacks for lockmanagers */
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