Really appreciate your help.
Thanks
Larry
------------------ Original ------------------
From: "valdis.kletnieks"<valdis.kletnieks@xxxxxx>;
Date: Sat, Aug 11, 2018 00:00 AM
To: "Larry"<losemyheaven@xxxxxxxxxxx>;
Cc: "kernelnewbies"<kernelnewbies@xxxxxxxxxxxxxxxxx>;
Subject: Re: A question on the function clean_bdev_bh_alias
> Does it intend to remove existent pages in block device's page cache
> if some new page cache of a vfs file was created whose block number
> range has overlaps with its block device page cache?
That's a situation you *really* hope doesn't arise.
Consider if you have (for example) an ext4 filesystem on /dev/sda4 mounted on
/foobar.
For there to be page cache for the ext4 filesystem and also page cache for
the block device, that means that something is writing to a file on /foobar
while something else is writing directly to /dev/sda4.
That's a really good way to corrupt the filesystem (and is why it's a Really
Bad Idea to fsck a mounted filesystem). And no, merely trimming cache
pages that overlap doesn't even come *close* to fixing the problem...
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