On Sun, 2011-01-23 at 09:18 +0100, Ronny Standtke wrote: > > See > > <http://kernel-handbook.alioth.debian.org/ch-common-tasks.html#s-common-off > > icial> - in particular, section 4.2.5, Simplified patching and building. > > OK, here is what I tried now: > ------------- > apt-get source linux-image-2.6.32-5-686 > cd linux-2.6-2.6.32 > bash debian/bin/test-patches ../000* > ------------- > > Unfortunately, this fails with the following error message: > ... > --> 30 fully applied. > --> Try to apply 30a~test. > (+) OK test/0001-Revert-aufs-narrow-down-the-BKL-region.patch > (+) OK test/0002-Revert-aufs-bugfix-unlock-mmap_sem-temporary-using- > B.patch > patch: **** malformed patch at line 182: @@ -630,25 +698,22 @@ static int > aufs_mmap(struct file *file, struct vm_area_struct *vma) > > (+) FAIL test/0003-aufs-bugfix-another-approach-to-keep-the-lock- [...]
Not sure how I did that, but try this version of patch 3 instead. Ben. -- Ben Hutchings Once a job is fouled up, anything done to improve it makes it worse.
From: J. R. Okajima <hooano...@yahoo.co.jp>
Date: Mon, 8 Mar 2010 23:45:56 +0900
Subject: [PATCH 3/4] aufs: bugfix, another approach to keep the lock order of mmap_sem
commit d986fa5a8557f6861fcac4106b6d75301bf5d118 in aufs2-2.6
The previous approach
4b70e6f aufs: bugfix, unlock mmap_sem temporary using BKL
was bad and already reverted.
This approach is ugly too, but it works.
- split aufs_mmap() into two parts.
- the first part is for copy-ing up which requires rwsem and executed by
aufsd workqueue.
- the second part is generic_file_mmap() and customizing vm_ops, and
executed by the original context.
- to protect customizing vm_ops from race between two mmaps, introduce a
new mutex in au_finfo. lock in the first phase, and release it in the
second. this is the most ugly part of this approach. if we could use
fi_rwsem for this use, we would use it. but there is no 'set_owner'
method for rwsem, but mutex has.
Signed-off-by: J. R. Okajima <hooano...@yahoo.co.jp>
[bwh: Adjust for 2.6.32]
---
fs/aufs/f_op.c | 113 +++++++++++++++++++++++++++++++++++++++++++------------
fs/aufs/file.h | 3 +
fs/aufs/finfo.c | 17 ++++++++
3 files changed, 109 insertions(+), 24 deletions(-)
diff --git a/fs/aufs/f_op.c b/fs/aufs/f_op.c
index 6f89992..32cc36f 100644
--- a/fs/aufs/f_op.c
+++ b/fs/aufs/f_op.c
@@ -77,6 +77,7 @@ int au_do_open_nondir(struct file *file, int flags)
finfo = au_fi(file);
finfo->fi_h_vm_ops = NULL;
finfo->fi_vm_ops = NULL;
+ mutex_init(&finfo->fi_mmap); /* regular file only? */
bindex = au_dbstart(dentry);
/* O_TRUNC is processed already */
BUG_ON(au_test_ro(dentry->d_sb, bindex, dentry->d_inode)
@@ -544,7 +545,7 @@ static int au_custom_vm_ops(struct au_finfo *finfo, struct vm_area_struct *vma)
int err;
struct vm_operations_struct *h_ops;
- AuRwMustAnyLock(&finfo->fi_rwsem);
+ MtxMustLock(&finfo->fi_mmap);
err = 0;
h_ops = finfo->fi_h_vm_ops;
@@ -570,49 +571,115 @@ static int au_custom_vm_ops(struct au_finfo *finfo, struct vm_area_struct *vma)
return err;
}
-static int aufs_mmap(struct file *file, struct vm_area_struct *vma)
+/*
+ * This is another ugly approach to keep the lock order, particularly
+ * mm->mmap_sem and aufs rwsem. The previous approach was reverted and you can
+ * find it in git-log, if you want.
+ *
+ * native readdir: i_mutex, copy_to_user, mmap_sem
+ * aufs readdir: i_mutex, rwsem, nested-i_mutex, copy_to_user, mmap_sem
+ *
+ * Before aufs_mmap() mmap_sem is acquired already, but aufs_mmap() has to
+ * acquire aufs rwsem. It introduces a circular locking dependency.
+ * To address this problem, aufs_mmap() delegates the part which requires aufs
+ * rwsem to its internal workqueue.
+ */
+
+/* very ugly approach */
+#ifdef CONFIG_DEBUG_MUTEXES
+#include <../kernel/mutex-debug.h>
+#else
+#include <../kernel/mutex.h>
+#endif
+
+struct au_mmap_pre_args {
+ /* input */
+ struct file *file;
+ struct vm_area_struct *vma;
+
+ /* output */
+ int *errp;
+ struct file *h_file;
+ int mmapped;
+};
+
+static int au_mmap_pre(struct file *file, struct vm_area_struct *vma,
+ struct file **h_file, int *mmapped)
{
int err;
- unsigned char wlock, mmapped;
+ const unsigned char wlock
+ = !!(file->f_mode & FMODE_WRITE) && (vma->vm_flags & VM_SHARED);
struct dentry *dentry;
struct super_block *sb;
- struct file *h_file;
- struct vm_operations_struct *vm_ops;
dentry = file->f_dentry;
- wlock = !!(file->f_mode & FMODE_WRITE) && (vma->vm_flags & VM_SHARED);
sb = dentry->d_sb;
- si_read_lock(sb, AuLock_FLUSH);
+ si_read_lock(sb, !AuLock_FLUSH);
err = au_reval_and_lock_fdi(file, au_reopen_nondir, /*wlock*/1);
if (unlikely(err))
goto out;
- mmapped = !!au_test_mmapped(file);
+ *mmapped = !!au_test_mmapped(file);
if (wlock) {
struct au_pin pin;
err = au_ready_to_write(file, -1, &pin);
- di_downgrade_lock(dentry, AuLock_IR);
+ di_write_unlock(dentry);
if (unlikely(err))
goto out_unlock;
au_unpin(&pin);
} else
- di_downgrade_lock(dentry, AuLock_IR);
+ di_write_unlock(dentry);
+ *h_file = au_h_fptr(file, au_fbstart(file));
+ get_file(*h_file);
+ au_fi_mmap_lock(file);
- h_file = au_h_fptr(file, au_fbstart(file));
- if (!mmapped && au_test_fs_bad_mapping(h_file->f_dentry->d_sb)) {
+out_unlock:
+ fi_write_unlock(file);
+out:
+ si_read_unlock(sb);
+ return err;
+}
+
+static void au_call_mmap_pre(void *args)
+{
+ struct au_mmap_pre_args *a = args;
+ *a->errp = au_mmap_pre(a->file, a->vma, &a->h_file, &a->mmapped);
+}
+
+static int aufs_mmap(struct file *file, struct vm_area_struct *vma)
+{
+ int err, wkq_err;
+ struct au_finfo *finfo;
+ struct dentry *h_dentry;
+ struct vm_operations_struct *vm_ops;
+ struct au_mmap_pre_args args = {
+ .file = file,
+ .vma = vma,
+ .errp = &err
+ };
+
+ wkq_err = au_wkq_wait(au_call_mmap_pre, &args);
+ if (unlikely(wkq_err))
+ err = wkq_err;
+ if (unlikely(err))
+ goto out;
+ finfo = au_fi(file);
+
+ h_dentry = args.h_file->f_dentry;
+ if (!args.mmapped && au_test_fs_bad_mapping(h_dentry->d_sb)) {
/*
* by this assignment, f_mapping will differs from aufs inode
* i_mapping.
* if someone else mixes the use of f_dentry->d_inode and
* f_mapping->host, then a problem may arise.
*/
- file->f_mapping = h_file->f_mapping;
+ file->f_mapping = args.h_file->f_mapping;
}
vm_ops = NULL;
- if (!mmapped) {
- vm_ops = au_vm_ops(h_file, vma);
+ if (!args.mmapped) {
+ vm_ops = au_vm_ops(args.h_file, vma);
err = PTR_ERR(vm_ops);
if (IS_ERR(vm_ops))
goto out_unlock;
@@ -630,25 +698,22 @@ static int aufs_mmap(struct file *file, struct vm_area_struct *vma)
goto out_unlock;
vma->vm_ops = &aufs_vm_ops;
- if (!mmapped) {
- struct au_finfo *finfo = au_fi(file);
-
+ if (!args.mmapped) {
finfo->fi_h_vm_ops = vm_ops;
mutex_init(&finfo->fi_vm_mtx);
}
- err = au_custom_vm_ops(au_fi(file), vma);
+ err = au_custom_vm_ops(finfo, vma);
if (unlikely(err))
goto out_unlock;
- vfsub_file_accessed(h_file);
- fsstack_copy_attr_atime(dentry->d_inode, h_file->f_dentry->d_inode);
+ vfsub_file_accessed(args.h_file);
+ fsstack_copy_attr_atime(file->f_dentry->d_inode, h_dentry->d_inode);
out_unlock:
- di_read_unlock(dentry, AuLock_IR);
- fi_write_unlock(file);
+ au_fi_mmap_unlock(file);
+ fput(args.h_file);
out:
- si_read_unlock(sb);
return err;
}
diff --git a/fs/aufs/file.h b/fs/aufs/file.h
index 4aaea9e..1d1d9d6 100644
--- a/fs/aufs/file.h
+++ b/fs/aufs/file.h
@@ -49,6 +49,7 @@ struct au_finfo {
struct vm_operations_struct *fi_h_vm_ops;
struct vm_operations_struct *fi_vm_ops;
struct mutex fi_vm_mtx;
+ struct mutex fi_mmap;
};
/* dir only */
@@ -114,6 +115,8 @@ void au_set_h_fptr(struct file *file, aufs_bindex_t bindex,
struct file *h_file);
void au_update_figen(struct file *file);
+void au_fi_mmap_lock(struct file *file);
+void au_fi_mmap_unlock(struct file *file);
void au_finfo_fin(struct file *file);
int au_finfo_init(struct file *file);
diff --git a/fs/aufs/finfo.c b/fs/aufs/finfo.c
index 4ab55e4..24ed4a1 100644
--- a/fs/aufs/finfo.c
+++ b/fs/aufs/finfo.c
@@ -56,6 +56,23 @@ void au_update_figen(struct file *file)
/* ---------------------------------------------------------------------- */
+void au_fi_mmap_lock(struct file *file)
+{
+ FiMustWriteLock(file);
+ lockdep_off();
+ mutex_lock(&au_fi(file)->fi_mmap);
+ lockdep_on();
+}
+
+void au_fi_mmap_unlock(struct file *file)
+{
+ lockdep_off();
+ mutex_unlock(&au_fi(file)->fi_mmap);
+ lockdep_on();
+}
+
+/* ---------------------------------------------------------------------- */
+
void au_finfo_fin(struct file *file)
{
struct au_finfo *finfo;
--
1.7.2.3
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