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    SubjectRe: [PATCH v6 00/19] Change readahead API
    On Tue, Feb 18, 2020 at 05:42:30AM -0800, Matthew Wilcox wrote:
    > On Tue, Feb 18, 2020 at 03:56:33PM +1100, Dave Chinner wrote:
    > > Latest version in your git tree:
    > >
    > > $ ▶ glo -n 5 willy/readahead
    > > 4be497096c04 mm: Use memalloc_nofs_save in readahead path
    > > ff63497fcb98 iomap: Convert from readpages to readahead
    > > 26aee60e89b5 iomap: Restructure iomap_readpages_actor
    > > 8115bcca7312 fuse: Convert from readpages to readahead
    > > 3db3d10d9ea1 f2fs: Convert from readpages to readahead
    > > $
    > >
    > > merged into a 5.6-rc2 tree fails at boot on my test vm:
    > >
    > > [ 2.423116] ------------[ cut here ]------------
    > > [ 2.424957] list_add double add: new=ffffea000efff4c8, prev=ffff8883bfffee60, next=ffffea000efff4c8.
    > > [ 2.428259] WARNING: CPU: 4 PID: 1 at lib/list_debug.c:29 __list_add_valid+0x67/0x70
    > > [ 2.457484] Call Trace:
    > > [ 2.458171] __pagevec_lru_add_fn+0x15f/0x2c0
    > > [ 2.459376] pagevec_lru_move_fn+0x87/0xd0
    > > [ 2.460500] ? pagevec_move_tail_fn+0x2d0/0x2d0
    > > [ 2.461712] lru_add_drain_cpu+0x8d/0x160
    > > [ 2.462787] lru_add_drain+0x18/0x20
    >
    > Are you sure that was 4be497096c04 ? I ask because there was a

    Yes, because it's the only version I've actually merged into my
    working tree, compiled and tried to run. :P

    > version pushed to that git tree that did contain a list double-add
    > (due to a mismerge when shuffling patches). I noticed it and fixed
    > it, and 4be497096c04 doesn't have that problem. I also test with
    > CONFIG_DEBUG_LIST turned on, but this problem you hit is going to be
    > probabilistic because it'll depend on the timing between whatever other
    > list is being used and the page actually being added to the LRU.

    I'll see if I can reproduce it.

    Cheers,

    Dave.
    --
    Dave Chinner
    david@fromorbit.com

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