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authorDipankar Sarma <dipankar@in.ibm.com>2005-09-09 13:04:13 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2005-09-09 13:57:55 -0700
commitab2af1f5005069321c5d130f09cce577b03f43ef (patch)
tree73a70ba486f522cd9eeeef376ede2b5a1c1b473b /fs/open.c
parent6e72ad2c581de121cc7e772469e2a8f6b1fd4379 (diff)
[PATCH] files: files struct with RCU
Patch to eliminate struct files_struct.file_lock spinlock on the reader side and use rcu refcounting rcuref_xxx api for the f_count refcounter. The updates to the fdtable are done by allocating a new fdtable structure and setting files->fdt to point to the new structure. The fdtable structure is protected by RCU thereby allowing lock-free lookup. For fd arrays/sets that are vmalloced, we use keventd to free them since RCU callbacks can't sleep. A global list of fdtable to be freed is not scalable, so we use a per-cpu list. If keventd is already handling the current cpu's work, we use a timer to defer queueing of that work. Since the last publication, this patch has been re-written to avoid using explicit memory barriers and use rcu_assign_pointer(), rcu_dereference() premitives instead. This required that the fd information is kept in a separate structure (fdtable) and updated atomically. Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'fs/open.c')
-rw-r--r--fs/open.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/fs/open.c b/fs/open.c
index b6542516a0c..2fac58c5191 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -24,6 +24,7 @@
#include <linux/personality.h>
#include <linux/pagemap.h>
#include <linux/syscalls.h>
+#include <linux/rcupdate.h>
#include <asm/unistd.h>
@@ -930,9 +931,8 @@ void fastcall fd_install(unsigned int fd, struct file * file)
struct fdtable *fdt;
spin_lock(&files->file_lock);
fdt = files_fdtable(files);
- if (unlikely(fdt->fd[fd] != NULL))
- BUG();
- fdt->fd[fd] = file;
+ BUG_ON(fdt->fd[fd] != NULL);
+ rcu_assign_pointer(fdt->fd[fd], file);
spin_unlock(&files->file_lock);
}
@@ -1024,7 +1024,7 @@ asmlinkage long sys_close(unsigned int fd)
filp = fdt->fd[fd];
if (!filp)
goto out_unlock;
- fdt->fd[fd] = NULL;
+ rcu_assign_pointer(fdt->fd[fd], NULL);
FD_CLR(fd, fdt->close_on_exec);
__put_unused_fd(files, fd);
spin_unlock(&files->file_lock);