On 04/23 2014 07:46 AM, Dave Chinner wrote: > On Tue, Apr 22, 2014 at 08:00:55PM +0800, Jeff Liu wrote: >> >> On 04/22 2014 14:59 PM, Dave Chinner wrote: >>> From: Dave Chinner <dchinner@xxxxxxxxxx> >>> >>> Commit e461fcb ("xfs: remote attribute lookups require the value >>> length") passes the remote attribute length in the xfs_da_args >>> structure on lookup so that CRC calculations and validity checking >>> can be performed correctly by related code. This, unfortunately has >>> the side effect of changing the args->valuelen parameter in cases >>> where it shouldn't. >>> >>> That is, when we replace a remote attribute, the incoming >>> replacement stores the value and length in args->value and >>> args->valuelen, but then the lookup which finds the existing remote >>> attribute overwrites args->valuelen with the length of the remote >>> attribute being replaced. Hence when we go to create the new >>> attribute, we create it of the size of the existing remote >>> attribute, not the size it is supposed to be. When the new attribute >>> is much smaller than the old attribute, this results in a >>> transaction overrun and an ASSERT() failure on a debug kernel: >>> >>> XFS: Assertion failed: tp->t_blk_res_used <= tp->t_blk_res, file: fs/xfs/xfs_trans.c, line: 331 >>> >>> Fix this by keeping the remote attribute value length separate to >>> the attribute value length in the xfs_da_args structure. The enables >>> us to pass the length of the remote attribute to be removed without >>> overwriting the new attribute's length. >>> >>> Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx> > .... >>> @@ -348,6 +348,11 @@ xfs_attr_rmtval_get( >>> >>> ASSERT(!(args->flags & ATTR_KERNOVAL)); >>> >>> + /* remote value might be different size to the buffer supplied. */ >>> + if (args->rmtvaluelen = args->valuelen) >> ^^^ >> Here is a typo... > > Oh, well spotted. > > But, hold on a minute, shouldn't gcc be catching those sorts of > typos? > > /me groans > > $ gcc t.c > $ gcc -Wall t.c > t.c: In function ¿main¿: > t.c:10:2: warning: suggest parentheses around assignment used as truth value [-Wparentheses] > if (foo = bar) > ^ > $ > > Only if -Wparentheses is specified. > > Why the hell are we suppressing useful warnings on the kernel build? > Well, maybe it's due to the different gcc release? I can hit this warning via gcc-4.8.1 which is the default version on Ubuntu 13.10 as below: # make SUBDIRS=fs/xfs -j4 ... fs/xfs/xfs_attr_remote.c: In function ‘xfs_attr_rmtval_get’: fs/xfs/xfs_attr_remote.c:352:2: warning: suggest parentheses around assignment used as truth value [-Wparentheses] if (args->rmtvaluelen = args->valuelen) ^ CC [M] fs/xfs/xfs_bmap_btree.o CC [M] fs/xfs/xfs_btree.o ... Thanks, -Jeff _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs