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| author | Dipankar Sarma <dipankar@in.ibm.com> | 2005-09-09 13:04:13 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2005-09-09 13:57:55 -0700 |
| commit | ab2af1f5005069321c5d130f09cce577b03f43ef (patch) | |
| tree | 73a70ba486f522cd9eeeef376ede2b5a1c1b473b /fs/fcntl.c | |
| parent | 6e72ad2c581de121cc7e772469e2a8f6b1fd4379 (diff) | |
| download | linux-3.10-ab2af1f5005069321c5d130f09cce577b03f43ef.tar.gz linux-3.10-ab2af1f5005069321c5d130f09cce577b03f43ef.tar.bz2 linux-3.10-ab2af1f5005069321c5d130f09cce577b03f43ef.zip | |
[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/fcntl.c')
| -rw-r--r-- | fs/fcntl.c | 13 |
1 files changed, 10 insertions, 3 deletions
diff --git a/fs/fcntl.c b/fs/fcntl.c index bfecc623808..d2f3ed8acd9 100644 --- a/fs/fcntl.c +++ b/fs/fcntl.c @@ -16,6 +16,7 @@ #include <linux/security.h> #include <linux/ptrace.h> #include <linux/signal.h> +#include <linux/rcupdate.h> #include <asm/poll.h> #include <asm/siginfo.h> @@ -64,8 +65,8 @@ static int locate_fd(struct files_struct *files, if (orig_start >= current->signal->rlim[RLIMIT_NOFILE].rlim_cur) goto out; - fdt = files_fdtable(files); repeat: + fdt = files_fdtable(files); /* * Someone might have closed fd's in the range * orig_start..fdt->next_fd @@ -95,9 +96,15 @@ repeat: if (error) goto repeat; + /* + * We reacquired files_lock, so we are safe as long as + * we reacquire the fdtable pointer and use it while holding + * the lock, no one can free it during that time. + */ + fdt = files_fdtable(files); if (start <= fdt->next_fd) fdt->next_fd = newfd + 1; - + error = newfd; out: @@ -163,7 +170,7 @@ asmlinkage long sys_dup2(unsigned int oldfd, unsigned int newfd) if (!tofree && FD_ISSET(newfd, fdt->open_fds)) goto out_fput; - fdt->fd[newfd] = file; + rcu_assign_pointer(fdt->fd[newfd], file); FD_SET(newfd, fdt->open_fds); FD_CLR(newfd, fdt->close_on_exec); spin_unlock(&files->file_lock); |