From: Hugh Dickins Date: Fri, 16 Nov 2012 22:15:04 +0000 (-0800) Subject: tmpfs: change final i_blocks BUG to WARNING X-Git-Tag: v3.2.35~73 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=79be252393312e96afcd0872e6ac0445e7398798;p=pandora-kernel.git tmpfs: change final i_blocks BUG to WARNING commit 0f3c42f522dc1ad7e27affc0a4aa8c790bce0a66 upstream. Under a particular load on one machine, I have hit shmem_evict_inode()'s BUG_ON(inode->i_blocks), enough times to narrow it down to a particular race between swapout and eviction. It comes from the "if (freed > 0)" asymmetry in shmem_recalc_inode(), and the lack of coherent locking between mapping's nrpages and shmem's swapped count. There's a window in shmem_writepage(), between lowering nrpages in shmem_delete_from_page_cache() and then raising swapped count, when the freed count appears to be +1 when it should be 0, and then the asymmetry stops it from being corrected with -1 before hitting the BUG. One answer is coherent locking: using tree_lock throughout, without info->lock; reasonable, but the raw_spin_lock in percpu_counter_add() on used_blocks makes that messier than expected. Another answer may be a further effort to eliminate the weird shmem_recalc_inode() altogether, but previous attempts at that failed. So far undecided, but for now change the BUG_ON to WARN_ON: in usual circumstances it remains a useful consistency check. Signed-off-by: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings --- Reading git-diff-tree failed