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Subject[059/116] NFS: Avoid a deadlock in nfs_release_page
2.6.32-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Trond Myklebust <Trond.Myklebust@netapp.com>

commit bb6fbc4548b9ae7ebbd06ef72f00229df259d217 upstream.

J.R. Okajima reports the following deadlock:

INFO: task kswapd0:305 blocked for more than 120 seconds.
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kswapd0 D 0000000000000001 0 305 2 0x00000000
ffff88001f21d4f0 0000000000000046 ffff88001fdea680 ffff88001f21c000
ffff88001f21dfd8 ffff88001f21c000 ffff88001f21dfd8 ffff88001f21dfd8
ffff88001fdea040 0000000000014c00 0000000000000001 ffff88001fdea040
Call Trace:
[<ffffffff8146155d>] io_schedule+0x4d/0x70
[<ffffffff810d2be5>] sync_page+0x65/0xa0
[<ffffffff81461b12>] __wait_on_bit_lock+0x52/0xb0
[<ffffffff810d2b80>] ? sync_page+0x0/0xa0
[<ffffffff810d2b64>] __lock_page+0x64/0x70
[<ffffffff81070ce0>] ? wake_bit_function+0x0/0x40
[<ffffffff810df1d4>] truncate_inode_pages_range+0x344/0x4a0
[<ffffffff810df340>] truncate_inode_pages+0x10/0x20
[<ffffffff8112cbfe>] generic_delete_inode+0x15e/0x190
[<ffffffff8112cc8d>] generic_drop_inode+0x5d/0x80
[<ffffffff8112bb88>] iput+0x78/0x80
[<ffffffff811bc908>] nfs_dentry_iput+0x38/0x50
[<ffffffff811285f4>] dentry_iput+0x84/0x110
[<ffffffff811286ae>] d_kill+0x2e/0x60
[<ffffffff8112912a>] dput+0x7a/0x170
[<ffffffff8111e925>] path_put+0x15/0x40
[<ffffffff811c3a44>] __put_nfs_open_context+0xa4/0xb0
[<ffffffff811cb5d0>] ? nfs_free_request+0x0/0x50
[<ffffffff811c3b0b>] put_nfs_open_context+0xb/0x10
[<ffffffff811cb5f9>] nfs_free_request+0x29/0x50
[<ffffffff81234b7e>] kref_put+0x8e/0xe0
[<ffffffff811cb594>] nfs_release_request+0x14/0x20
[<ffffffff811cf769>] nfs_find_and_lock_request+0x89/0xa0
[<ffffffff811d1180>] nfs_wb_page+0x80/0x110
[<ffffffff811c0770>] nfs_release_page+0x70/0x90
[<ffffffff810d18ee>] try_to_release_page+0x5e/0x80
[<ffffffff810e1178>] shrink_page_list+0x638/0x860
[<ffffffff810e19de>] shrink_zone+0x63e/0xc40
We can fix this by making the call to put_nfs_open_context() happen when we
actually remove the write request from the inode (which is done by the
nfsiod thread in this case).

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
fs/nfs/pagelist.c | 23 +++++++++++++----------
1 file changed, 13 insertions(+), 10 deletions(-)
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -112,12 +112,10 @@ void nfs_unlock_request(struct nfs_page
*/
int nfs_set_page_tag_locked(struct nfs_page *req)
{
- struct nfs_inode *nfsi = NFS_I(req->wb_context->path.dentry->d_inode);
-
if (!nfs_lock_request_dontget(req))
return 0;
if (req->wb_page != NULL)
- radix_tree_tag_set(&nfsi->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_LOCKED);
+ radix_tree_tag_set(&NFS_I(req->wb_context->path.dentry->d_inode)->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_LOCKED);
return 1;
}

@@ -126,10 +124,10 @@ int nfs_set_page_tag_locked(struct nfs_p
*/
void nfs_clear_page_tag_locked(struct nfs_page *req)
{
- struct inode *inode = req->wb_context->path.dentry->d_inode;
- struct nfs_inode *nfsi = NFS_I(inode);
-
if (req->wb_page != NULL) {
+ struct inode *inode = req->wb_context->path.dentry->d_inode;
+ struct nfs_inode *nfsi = NFS_I(inode);
+
spin_lock(&inode->i_lock);
radix_tree_tag_clear(&nfsi->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_LOCKED);
nfs_unlock_request(req);
@@ -142,16 +140,22 @@ void nfs_clear_page_tag_locked(struct nf
* nfs_clear_request - Free up all resources allocated to the request
* @req:
*
- * Release page resources associated with a write request after it
- * has completed.
+ * Release page and open context resources associated with a read/write
+ * request after it has completed.
*/
void nfs_clear_request(struct nfs_page *req)
{
struct page *page = req->wb_page;
+ struct nfs_open_context *ctx = req->wb_context;
+
if (page != NULL) {
page_cache_release(page);
req->wb_page = NULL;
}
+ if (ctx != NULL) {
+ put_nfs_open_context(ctx);
+ req->wb_context = NULL;
+ }
}


@@ -165,9 +169,8 @@ static void nfs_free_request(struct kref
{
struct nfs_page *req = container_of(kref, struct nfs_page, wb_kref);

- /* Release struct file or cached credential */
+ /* Release struct file and open context */
nfs_clear_request(req);
- put_nfs_open_context(req->wb_context);
nfs_page_free(req);
}




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