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authorLinus Torvalds <torvalds@linux-foundation.org>2009-04-02 21:09:10 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-04-02 21:09:10 -0700
commit8fe74cf053de7ad2124a894996f84fa890a81093 (patch)
tree77dcd8fbf33ce53a3821942233962fb28c6f2848 /kernel/fork.c
parentc2eb2fa6d2b6fe122d3479ec5b28d978418b2698 (diff)
parentced117c73edc917e96dea7cca98c91383f0792f7 (diff)
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6: Remove two unneeded exports and make two symbols static in fs/mpage.c Cleanup after commit 585d3bc06f4ca57f975a5a1f698f65a45ea66225 Trim includes of fdtable.h Don't crap into descriptor table in binfmt_som Trim includes in binfmt_elf Don't mess with descriptor table in load_elf_binary() Get rid of indirect include of fs_struct.h New helper - current_umask() check_unsafe_exec() doesn't care about signal handlers sharing New locking/refcounting for fs_struct Take fs_struct handling to new file (fs/fs_struct.c) Get rid of bumping fs_struct refcount in pivot_root(2) Kill unsharing fs_struct in __set_personality()
Diffstat (limited to 'kernel/fork.c')
-rw-r--r--kernel/fork.c63
1 files changed, 28 insertions, 35 deletions
diff --git a/kernel/fork.c b/kernel/fork.c
index f7445823144..660c2b8765b 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -60,6 +60,7 @@
#include <linux/tty.h>
#include <linux/proc_fs.h>
#include <linux/blkdev.h>
+#include <linux/fs_struct.h>
#include <trace/sched.h>
#include <linux/magic.h>
@@ -681,38 +682,21 @@ fail_nomem:
return retval;
}
-static struct fs_struct *__copy_fs_struct(struct fs_struct *old)
-{
- struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
- /* We don't need to lock fs - think why ;-) */
- if (fs) {
- atomic_set(&fs->count, 1);
- rwlock_init(&fs->lock);
- fs->umask = old->umask;
- read_lock(&old->lock);
- fs->root = old->root;
- path_get(&old->root);
- fs->pwd = old->pwd;
- path_get(&old->pwd);
- read_unlock(&old->lock);
- }
- return fs;
-}
-
-struct fs_struct *copy_fs_struct(struct fs_struct *old)
-{
- return __copy_fs_struct(old);
-}
-
-EXPORT_SYMBOL_GPL(copy_fs_struct);
-
static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
{
+ struct fs_struct *fs = current->fs;
if (clone_flags & CLONE_FS) {
- atomic_inc(&current->fs->count);
+ /* tsk->fs is already what we want */
+ write_lock(&fs->lock);
+ if (fs->in_exec) {
+ write_unlock(&fs->lock);
+ return -EAGAIN;
+ }
+ fs->users++;
+ write_unlock(&fs->lock);
return 0;
}
- tsk->fs = __copy_fs_struct(current->fs);
+ tsk->fs = copy_fs_struct(fs);
if (!tsk->fs)
return -ENOMEM;
return 0;
@@ -1544,12 +1528,16 @@ static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
{
struct fs_struct *fs = current->fs;
- if ((unshare_flags & CLONE_FS) &&
- (fs && atomic_read(&fs->count) > 1)) {
- *new_fsp = __copy_fs_struct(current->fs);
- if (!*new_fsp)
- return -ENOMEM;
- }
+ if (!(unshare_flags & CLONE_FS) || !fs)
+ return 0;
+
+ /* don't need lock here; in the worst case we'll do useless copy */
+ if (fs->users == 1)
+ return 0;
+
+ *new_fsp = copy_fs_struct(fs);
+ if (!*new_fsp)
+ return -ENOMEM;
return 0;
}
@@ -1665,8 +1653,13 @@ SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
if (new_fs) {
fs = current->fs;
+ write_lock(&fs->lock);
current->fs = new_fs;
- new_fs = fs;
+ if (--fs->users)
+ new_fs = NULL;
+ else
+ new_fs = fs;
+ write_unlock(&fs->lock);
}
if (new_mm) {
@@ -1705,7 +1698,7 @@ bad_unshare_cleanup_sigh:
bad_unshare_cleanup_fs:
if (new_fs)
- put_fs_struct(new_fs);
+ free_fs_struct(new_fs);
bad_unshare_cleanup_thread:
bad_unshare_out: