difficult to pinpoint exhaustion of swap between 4.2.0-rc6 and 4.2.0-rc7

[Arthur Marsh]

Hi, I've found that the Linus' git head kernel has had some unwelcome 
behaviour where chromium browser would exhaust all swap space in the 
course of a few hours. The behaviour appeared before the release of 
4.2.0-rc7.

This does not happen with kernel 4.2.0-rc6.

When I tried a git-bisect, the results where not conclusive due to the 
problem taking over an hour to appear after booting, the closest I came 
was around this commit (the actual problem may be a few commits either 
side):

git bisect good
4f258a46346c03fa0bbb6199ffaf4e1f9f599660 is the first bad commit
commit 4f258a46346c03fa0bbb6199ffaf4e1f9f599660
Author: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
Date:   Tue Jun 23 12:13:59 2015 -0400

    sd: Fix maximum I/O size for BLOCK_PC requests

    Commit bcdb247c6b6a ("sd: Limit transfer length") clamped the maximum
    size of an I/O request to the MAXIMUM TRANSFER LENGTH field in the 
BLOCK
    LIMITS VPD. This had the unfortunate effect of also limiting the 
maximum
    size of non-filesystem requests sent to the device through sg/bsg.

    Avoid using blk_queue_max_hw_sectors() and set the max_sectors queue
    limit directly.

    Also update the comment in blk_limits_max_hw_sectors() to clarify that
    max_hw_sectors defines the limit for the I/O controller only.

    Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
    Reported-by: Brian King <brking@xxxxxxxxxxxxxxxxxx>
    Tested-by: Brian King <brking@xxxxxxxxxxxxxxxxxx>
    Cc: stable@xxxxxxxxxxxxxxx # 3.17+
    Signed-off-by: James Bottomley <JBottomley@xxxxxxxx>

:040000 040000 fbd0519d9ee0a8f92a7dab9a9c6d7b7868974fba 
b4cf554c568813704993538008aed5b704624679 M      block
:040000 040000 f2630c903cd36ede2619d173f9d1ea0d725ea111 
ff6b6f732afbf6f4b6b26a827c463de50f0e356c M      drivers

Has anyone seen a similar problem?
I can supply .config and other information if requested.

Arthur.

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