[f2fs-dev] [Bug 219484] f2fs discard causes kernel NULL pointer dereferencing

[bugzilla-daemon--- via Linux-f2fs-devel <linux-f2fs-devel@lists.sourceforge.net>]

https://bugzilla.kernel.org/show_bug.cgi?id=219484

Chao Yu (chao@kernel.org) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
                 CC|                            |chao@kernel.org

--- Comment #1 from Chao Yu (chao@kernel.org) ---
Hi, thanks for your report.

Can you please help to check max_hw_discard_sectors parameter of dm device
via "cat /sys/block/<device_name>/queue/max_hw_discard_sectors"?

I doubt max_discard_blocks becomes zero in __submit_discard_cmd(), result
in that __blkdev_issue_discard() fails to allocate bio.

__submit_discard_cmd()
{
        unsigned int max_discard_blocks =
                        SECTOR_TO_BLOCK(bdev_max_discard_sectors(bdev));
...
        while () {
...
                if (len > max_discard_blocks) {
                        len = max_discard_blocks;
                        last = false;
                }
...
                } else {
                        err = __blkdev_issue_discard(bdev,
                                        SECTOR_FROM_BLOCK(start),
                                        SECTOR_FROM_BLOCK(len),
                                        GFP_NOFS, &bio);
                }
...
                f2fs_bug_on(sbi, !bio); // trigger warning here and panic below
}

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