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fs/locks.c: prepare for BKL removal

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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 and ceph might sleep, but we can 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 to use a spinlock from Matthew
Wilcox, who has attempted this a few times before, the
earliest patch from over 10 years ago turned it into
a semaphore, which ended up being slower than the BKL
and was subsequently reverted.

Someone should do some serious performance testing when
this becomes a spinlock, since this has caused problems
before. Using a spinlock should be at least as good
as the BKL in theory, but who knows...

Signed-off-by: Arnd Bergmann <[email protected]>
Acked-by: Matthew Wilcox <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Trond Myklebust <[email protected]>
Cc: "J. Bruce Fields" <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Miklos Szeredi <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: John Kacur <[email protected]>
Cc: Sage Weil <[email protected]>
Cc: [email protected]
Cc: [email protected]
This commit is contained in:
Arnd Bergmann 2010-09-18 15:09:31 +02:00
commit b89f432133
8 changed files with 97 additions and 66 deletions
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6
fs/nfsd/nfs4state.c
View file

@ -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;
}