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fasync: re-organize fasync entry insertion to allow it under a spinlock

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You currently cannot use "fasync_helper()" in an atomic environment to
insert a new fasync entry, because it will need to allocate the new
"struct fasync_struct".

Yet fcntl_setlease() wants to call this under lock_flocks(), which is in
the process of being converted from the BKL to a spinlock.

In order to fix this, this abstracts out the actual fasync list
insertion and the fasync allocations into functions of their own, and
teaches fs/locks.c to pre-allocate the fasync_struct entry.  That way
the actual list insertion can happen while holding the required
spinlock.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[bfields@redhat.com: rebase on top of my changes to Arnd's patch]
Tested-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
This commit is contained in:
Linus Torvalds
2010-10-27 12:38:12 -04:00
committed by Arnd Bergmann
parent c5b1f0d92c
commit f7347ce4ee
3 changed files with 74 additions and 19 deletions
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fs/locks.c
+17 -1
View File
@@ -1505,6 +1505,7 @@ EXPORT_SYMBOL_GPL(vfs_setlease);
int fcntl_setlease(unsigned int fd, struct file *filp, long arg)
{
struct file_lock *fl;
struct fasync_struct *new;
struct inode *inode = filp->f_path.dentry->d_inode;
int error;
@@ -1512,12 +1513,25 @@ int fcntl_setlease(unsigned int fd, struct file *filp, long 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, &fl);
if (error || arg == F_UNLCK)
goto out_unlock;
error = fasync_helper(fd, filp, 1, &fl->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 */
fl->fl_type = F_UNLCK | F_INPROGRESS;
@@ -1529,6 +1543,8 @@ 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;
}