Hi Minchan, On Tue, Feb 6, 2018 at 2:01 PM, Minchan Kim <minc...@kernel.org> wrote: [...] > On Mon, Feb 05, 2018 at 04:49:03PM -0800, Joel Fernandes wrote: >> During invocation of ashmem shrinker under memory pressure, ashmem >> calls into VFS code via vfs_fallocate. We however make sure we >> don't enter it if the allocation was GFP_FS to prevent looping >> into filesystem code. However lockdep doesn't know this and prints >> a lockdep splat as below. >> >> This patch fixes the issue by releasing the reclaim_fs lock after >> checking for GFP_FS but before calling into the VFS path, and >> reacquiring it after so that lockdep can continue reporting any >> reclaim issues later. > > At first glance, it looks reasonable. However, Couldn't we return > just 0 in ashmem_shrink_count when the context is under FS? >
We're already checking if GFP_FS in ashmem_shrink_scan and bailing out though, did I miss something? The problem is not that there is a deadlock that occurs, the problem that even when we're not under FS, lockdep reports an issue that can't happen. The fix is for the lockdep false positive that occurs. thanks, - Joel
