From: Fred Isaman Date: Wed, 19 Mar 2008 15:24:39 +0000 (-0400) Subject: nfs: don't ignore return value from nfs_pageio_add_request X-Git-Tag: v2.6.25-rc7~56^2 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f8512ad0da16cbe156f3a7627971cdf0b39c4138;p=pandora-kernel.git 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 --- Reading git-diff-tree failed