[PATCH 2.4.21-pre] Fix possible SMP race in nfs_sync_page()

From: Trond Myklebust (trond.myklebust@fys.uio.no)
Date: Thu Dec 12 2002 - 05:26:58 EST

Hi Marcelo,

  The following patch fixes a race in nfs_sync_page() whereby one
thread may call the generic sync_page() and then block on a given page
while another thread is working in mapping->a_ops->readpage().

Cheers,
  Trond

diff -u --recursive --new-file linux-2.4.21-pre1/fs/nfs/file.c linux-2.4.21-01-nfs_sync/fs/nfs/file.c
--- linux-2.4.21-pre1/fs/nfs/file.c 2002-02-05 15:10:21.000000000 +0100
+++ linux-2.4.21-01-nfs_sync/fs/nfs/file.c 2002-12-12 11:23:09.000000000 +0100
@@ -187,6 +187,7 @@
         if (!inode)
                 return 0;
 
+ NFS_SetPageSync(page);
         rpages = NFS_SERVER(inode)->rpages;
         result = nfs_pagein_inode(inode, index, rpages);
         if (result < 0)
diff -u --recursive --new-file linux-2.4.21-pre1/fs/nfs/read.c linux-2.4.21-01-nfs_sync/fs/nfs/read.c
--- linux-2.4.21-pre1/fs/nfs/read.c 2002-10-06 01:03:40.000000000 +0200
+++ linux-2.4.21-01-nfs_sync/fs/nfs/read.c 2002-12-12 11:23:09.000000000 +0100
@@ -171,11 +171,16 @@
         struct nfs_page *new;
 
         new = nfs_create_request(nfs_file_cred(file), inode, page, 0, PAGE_CACHE_SIZE);
- if (IS_ERR(new))
+ if (IS_ERR(new)) {
+ SetPageError(page);
+ NFS_ClearPageSync(page);
+ UnlockPage(page);
                 return PTR_ERR(new);
+ }
         nfs_mark_request_read(new);
 
- if (inode->u.nfs_i.nread >= NFS_SERVER(inode)->rpages ||
+ if (NFS_TestClearPageSync(page) ||
+ inode->u.nfs_i.nread >= NFS_SERVER(inode)->rpages ||
             page_index(page) == (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT)
                 nfs_pagein_inode(inode, 0, 0);
         return 0;
@@ -222,6 +227,7 @@
                 req = nfs_list_entry(head->next);
                 page = req->wb_page;
                 nfs_list_remove_request(req);
+ NFS_ClearPageSync(page);
                 SetPageError(page);
                 UnlockPage(page);
                 nfs_clear_request(req);
@@ -429,6 +435,7 @@
                 } else
                         SetPageError(page);
                 flush_dcache_page(page);
+ NFS_ClearPageSync(page);
                 UnlockPage(page);
 
                 dprintk("NFS: read (%x/%Ld %d@%Ld)\n",
@@ -482,6 +489,7 @@
         return error;
 
 out_error:
+ NFS_ClearPageSync(page);
         UnlockPage(page);
         goto out;
 }
diff -u --recursive --new-file linux-2.4.21-pre1/include/linux/mm.h linux-2.4.21-01-nfs_sync/include/linux/mm.h
--- linux-2.4.21-pre1/include/linux/mm.h 2002-03-27 00:11:32.000000000 +0100
+++ linux-2.4.21-01-nfs_sync/include/linux/mm.h 2002-12-12 11:23:09.000000000 +0100
@@ -297,6 +297,7 @@
 #define PG_arch_1 13
 #define PG_reserved 14
 #define PG_launder 15 /* written out by VM pressure.. */
+#define PG_fs_1 16 /* Filesystem specific */
 
 /* Make it prettier to test the above... */
 #define UnlockPage(page) unlock_page(page)
diff -u --recursive --new-file linux-2.4.21-pre1/include/linux/nfs_fs.h linux-2.4.21-01-nfs_sync/include/linux/nfs_fs.h
--- linux-2.4.21-pre1/include/linux/nfs_fs.h 2002-10-15 18:32:18.000000000 +0200
+++ linux-2.4.21-01-nfs_sync/include/linux/nfs_fs.h 2002-12-12 11:23:09.000000000 +0100
@@ -269,6 +269,10 @@
 extern int nfs_scan_lru_read(struct nfs_server *, struct list_head *);
 extern int nfs_scan_lru_read_timeout(struct nfs_server *, struct list_head *);
 
+#define NFS_SetPageSync(page) set_bit(PG_fs_1, &(page)->flags)
+#define NFS_ClearPageSync(page) clear_bit(PG_fs_1, &(page)->flags)
+#define NFS_TestClearPageSync(page) test_and_clear_bit(PG_fs_1, &(page)->flags)
+
 /*
  * linux/fs/mount_clnt.c
  * (Used only by nfsroot module)

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This archive was generated by hypermail 2b29 : Sun Dec 15 2002 - 22:00:24 EST