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authorTrond Myklebust <Trond.Myklebust@netapp.com>2007-10-18 17:08:05 -0400
committerTrond Myklebust <Trond.Myklebust@netapp.com>2007-10-19 17:18:57 -0400
commit61e930a904966cc37e0a3404276f0b73037e57ca (patch)
tree65553920bd6a471c2bae5a35ed3b4cee8bdf1258
parent4fa4d23fa20de67df919030c1216295664866ad7 (diff)
NFS: Fix a writeback race...
This patch fixes a regression that was introduced by commit 44dd151d5c21234cc534c47d7382f5c28c3143cd We cannot zero the user page in nfs_mark_uptodate() any more, since a) We'd be modifying the page without holding the page lock b) We can race with other updates of the page, most notably because of the call to nfs_wb_page() in nfs_writepage_setup(). Instead, we do the zeroing in nfs_update_request() if we see that we're creating a request that might potentially be marked as up to date. Thanks to Olivier Paquet for reporting the bug and providing a test-case. Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
-rw-r--r--fs/nfs/write.c17
1 files changed, 13 insertions, 4 deletions
diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 0cf9d1cd9bd2..89527a487ed7 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -174,8 +174,6 @@ static void nfs_mark_uptodate(struct page *page, unsigned int base, unsigned int
return;
if (count != nfs_page_length(page))
return;
- if (count != PAGE_CACHE_SIZE)
- zero_user_page(page, count, PAGE_CACHE_SIZE - count, KM_USER0);
SetPageUptodate(page);
}
@@ -627,7 +625,8 @@ static struct nfs_page * nfs_update_request(struct nfs_open_context* ctx,
return ERR_PTR(error);
}
spin_unlock(&inode->i_lock);
- return new;
+ req = new;
+ goto zero_page;
}
spin_unlock(&inode->i_lock);
@@ -655,13 +654,23 @@ static struct nfs_page * nfs_update_request(struct nfs_open_context* ctx,
if (offset < req->wb_offset) {
req->wb_offset = offset;
req->wb_pgbase = offset;
- req->wb_bytes = rqend - req->wb_offset;
+ req->wb_bytes = max(end, rqend) - req->wb_offset;
+ goto zero_page;
}
if (end > rqend)
req->wb_bytes = end - req->wb_offset;
return req;
+zero_page:
+ /* If this page might potentially be marked as up to date,
+ * then we need to zero any uninitalised data. */
+ if (req->wb_pgbase == 0 && req->wb_bytes != PAGE_CACHE_SIZE
+ && !PageUptodate(req->wb_page))
+ zero_user_page(req->wb_page, req->wb_bytes,
+ PAGE_CACHE_SIZE - req->wb_bytes,
+ KM_USER0);
+ return req;
}
int nfs_flush_incompatible(struct file *file, struct page *page)