From f8512ad0da16cbe156f3a7627971cdf0b39c4138 Mon Sep 17 00:00:00 2001 From: Fred Isaman Date: Wed, 19 Mar 2008 11:24:39 -0400 Subject: nfs: don't ignore return value from nfs_pageio_add_request Ignoring the return value from nfs_pageio_add_request can cause deadlocks. In read path: call nfs_pageio_add_request from readpage_async_filler assume at this point that there are requests already in desc, that can't be merged with the current request. so nfs_pageio_doio is fired up to clear out desc. assume something goes wrong in setting up the io, so desc->pg_error is set. This causes nfs_pageio_add_request to return 0, *WITHOUT* adding the original request. BUT, since return code is ignored, readpage_async_filler assumes it has been added, and does nothing further, leaving page locked. do_generic_mapping_read will eventually call lock_page, resulting in deadlock In write path: page is marked dirty by generic_perform_write nfs_writepages is called call nfs_pageio_add_request from nfs_page_async_flush assume at this point that there are requests already in desc, that can't be merged with the current request. so nfs_pageio_doio is fired up to clear out desc. assume something goes wrong in setting up the io, so desc->pg_error is set. This causes nfs_page_async_flush to return 0, *WITHOUT* adding the original request, yet marking the request as locked (PG_BUSY) and in writeback, clearing dirty marks. The next time a write is done to the page, deadlock will result as nfs_write_end calls nfs_update_request Signed-off-by: Fred Isaman Signed-off-by: Trond Myklebust --- fs/nfs/read.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'fs/nfs/read.c') diff --git a/fs/nfs/read.c b/fs/nfs/read.c index 3d7d9631e12..5a70be589bb 100644 --- a/fs/nfs/read.c +++ b/fs/nfs/read.c @@ -533,7 +533,10 @@ readpage_async_filler(void *data, struct page *page) if (len < PAGE_CACHE_SIZE) zero_user_segment(page, len, PAGE_CACHE_SIZE); - nfs_pageio_add_request(desc->pgio, new); + if (!nfs_pageio_add_request(desc->pgio, new)) { + error = desc->pgio->pg_error; + goto out_unlock; + } return 0; out_error: error = PTR_ERR(new); -- cgit v1.2.3