Re: [PATCH] block: don't warn when calling fsync on read-only block devices

On 9/3/18 4:05 PM, Mikulas Patocka wrote:

On Wed, 22 Aug 2018, Jens Axboe wrote:

quoted

On 8/22/18 10:23 AM, Mikulas Patocka wrote:

quoted

It is possible to call fsync on a read-only handle (for example, fsck.ext2 
does it when doing read-only check), and this call results in kernel 
warning. This bug was introduced by the commit 721c7fc701c7 "block: fail 
op_is_write() requests to read-only partitions".

Similar patch is already queued up, it'll go into Linus's tree before
-rc1.

-- 
Jens Axboe

I think you mean the patch b089cfd95d32638335c551651a8e00fd2c4edb0b, but 
it doesn't work.

The first problem is that bio_op returns the opcode, but op_is_flush 
expects flags as its parameter. bio_op strips off the flags, and so the 
condition op_is_flush is never true and the warning is not shut off.

Anoher problem is that the flags REQ_FUA and REQ_PREFLUSH may be 
superimposed on regular write bio and in that case the warning should be 
triggered. We want to shut the warning off only if bio_sectors is zero 
(i.e. if the flush request is not superimposed on regular write).

Thanks for fixing that up, that was somewhat of a disaster. Applied.

-- 
Jens Axboe