Re: [BUG] problem with nfs_invalidate_page
From: Trond Myklebust
Date: Wed Aug 29 2007 - 11:49:47 EST
On Tue, 2007-08-28 at 17:32 +0900, Ryusuke Konishi wrote:
> On Mon, 27 Aug 2007 09:30:12 -0400, Trond Myklebust wrote:
> >It looks as if ecryptfs is dropping the page lock between the calls to
> >prepare_write() and commit_write(). That would be a bug.
>
> No, ecryptfs is holding the page lock between the calls to
> nfs_prepare_write() and nfs_commit_write().
> This is a regression since kernel 2.6.20; kernel 2.6.19 does not
> yield the BUG.
>
> Please look at truncate_complete_page() and nfs_wb_page_priority()
> which is called from nfs_invalidate_page().
>
> The recent truncate_complete_page() clears the dirty flag from a page
> before calling a_ops->invalidatepage(),
> ^^^^^^
> static void
> truncate_complete_page(struct address_space *mapping, struct page *page)
> {
> ...
> cancel_dirty_page(page, PAGE_CACHE_SIZE); <--- Inserted here at kernel 2.6.20
>
> if (PagePrivate(page))
> do_invalidatepage(page, 0); ---> will call a_ops->invalidatepage()
> ...
> }
>
> and this is disturbing nfs_wb_page_priority() from calling
> nfs_writepage_locked() that is expected to handle the pending
> request (=nfs_page) associated with the page.
>
> int nfs_wb_page_priority(struct inode *inode, struct page *page, int how)
> {
> ...
> if (clear_page_dirty_for_io(page)) {
> ret = nfs_writepage_locked(page, &wbc);
> if (ret < 0)
> goto out;
> }
> ...
> }
>
> Since truncate_complete_page() will get rid of the page after
> a_ops->invalidatepage() returns, the request (=nfs_page) associated
> with the page becomes a garbage in nfs_inode->nfs_page_tree.
>
> This causes the collision of nfs_page and yields the BUG.
>
>
> Cheers,
> Ryusuke Konishi
OK. I see your point... Basically, you are saying that the new
->invalidatepage() semantics do not allow us to rely on the dirty status
of the page in order to figure out if we need to clean up.
Andrew, that was a fairly significant change in semantics...
Anyhow, well done debugging it! Does the following patch fix the Oops?
Trond
--- Begin Message ---
Ryusuke Konishi says:
The recent truncate_complete_page() clears the dirty flag from a page
before calling a_ops->invalidatepage(),
^^^^^^
static void
truncate_complete_page(struct address_space *mapping, struct page *page)
{
...
cancel_dirty_page(page, PAGE_CACHE_SIZE); <--- Inserted here at
kernel 2.6.20
if (PagePrivate(page))
do_invalidatepage(page, 0); ---> will call
a_ops->invalidatepage()
...
}
and this is disturbing nfs_wb_page_priority() from calling
nfs_writepage_locked() that is expected to handle the pending
request (=nfs_page) associated with the page.
int nfs_wb_page_priority(struct inode *inode, struct page *page, int how)
{
...
if (clear_page_dirty_for_io(page)) {
ret = nfs_writepage_locked(page, &wbc);
if (ret < 0)
goto out;
}
...
}
Since truncate_complete_page() will get rid of the page after
a_ops->invalidatepage() returns, the request (=nfs_page) associated
with the page becomes a garbage in nfs_inode->nfs_page_tree.
------------------------
Fix this by ensuring that nfs_wb_page_priority() recognises that it may
also need to clear out non-dirty pages that have an nfs_page associated
with them.
Signed-off-by: Trond Myklebust <Trond.Myklebust@xxxxxxxxxx>
---
fs/nfs/file.c | 2 +-
fs/nfs/write.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
include/linux/nfs_fs.h | 1 +
3 files changed, 46 insertions(+), 1 deletions(-)
diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index c87dc71..579cf8a 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -316,7 +316,7 @@ static void nfs_invalidate_page(struct page *page, unsigned long offset)
if (offset != 0)
return;
/* Cancel any unstarted writes on this page */
- nfs_wb_page_priority(page->mapping->host, page, FLUSH_INVALIDATE);
+ nfs_wb_page_cancel(page->mapping->host, page);
}
static int nfs_release_page(struct page *page, gfp_t gfp)
diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index ef97e0c..0d7a77c 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -1396,6 +1396,50 @@ out:
return ret;
}
+int nfs_wb_page_cancel(struct inode *inode, struct page *page)
+{
+ struct nfs_page *req;
+ loff_t range_start = page_offset(page);
+ loff_t range_end = range_start + (loff_t)(PAGE_CACHE_SIZE - 1);
+ struct writeback_control wbc = {
+ .bdi = page->mapping->backing_dev_info,
+ .sync_mode = WB_SYNC_ALL,
+ .nr_to_write = LONG_MAX,
+ .range_start = range_start,
+ .range_end = range_end,
+ };
+ int ret = 0;
+
+ BUG_ON(!PageLocked(page));
+ for (;;) {
+ req = nfs_page_find_request(page);
+ if (req == NULL)
+ goto out;
+ if (test_bit(PG_NEED_COMMIT, &req->wb_flags)) {
+ nfs_release_request(req);
+ break;
+ }
+ if (nfs_lock_request_dontget(req)) {
+ nfs_inode_remove_request(req);
+ /*
+ * In case nfs_inode_remove_request has marked the
+ * page as being dirty
+ */
+ cancel_dirty_page(page, PAGE_CACHE_SIZE);
+ nfs_unlock_request(req);
+ break;
+ }
+ ret = nfs_wait_on_request(req);
+ if (ret < 0)
+ goto out;
+ }
+ if (!PagePrivate(page))
+ return 0;
+ ret = nfs_sync_mapping_wait(page->mapping, &wbc, FLUSH_INVALIDATE);
+out:
+ return ret;
+}
+
int nfs_wb_page_priority(struct inode *inode, struct page *page, int how)
{
loff_t range_start = page_offset(page);
diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index 157dcb0..7250eea 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -431,6 +431,7 @@ extern int nfs_sync_mapping_range(struct address_space *, loff_t, loff_t, int);
extern int nfs_wb_all(struct inode *inode);
extern int nfs_wb_page(struct inode *inode, struct page* page);
extern int nfs_wb_page_priority(struct inode *inode, struct page* page, int how);
+extern int nfs_wb_page_cancel(struct inode *inode, struct page* page);
#if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
extern int nfs_commit_inode(struct inode *, int);
extern struct nfs_write_data *nfs_commit_alloc(void);
--- End Message ---