Messages in this thread | | | Date | Sun, 5 Apr 2015 22:54:46 +0100 | From | Al Viro <> | Subject | Re: [PATCH 02/16] vfs: check kiocb->ki_flags instead filp->fl_flags |
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On Sun, Apr 05, 2015 at 07:11:45PM +0100, Al Viro wrote: > On Sun, Apr 05, 2015 at 02:03:22PM +0300, Dmitry Monakhov wrote: > > > I'm not sure I have get your point about ocfs2 because it does > > iov_iter_truncate() right after generic_write_checks() > > This > ret = ocfs2_prepare_inode_for_write(file, ppos, count, appending, > &can_do_direct, &has_refcount); > being done before generic_write_checks(). It actually duplicates some > parts of generic_write_checks() inside (O_APPEND-related, and AFAICS > they _are_ triggered twice that way).
XFS seems to be buggered as well: /* DIO must be aligned to device logical sector size */ if ((pos | count) & target->bt_logical_sectormask) return -EINVAL;
/* "unaligned" here means not aligned to a filesystem block */ if ((pos & mp->m_blockmask) || ((pos + count) & mp->m_blockmask)) unaligned_io = 1; ... ret = xfs_file_aio_write_checks(file, &pos, &count, &iolock);
now, play with rlimit() and suddenly the alignment checks above have nothing to do with what'll actually happen after that sucker - it's calling generic_write_checks(), so...
Incidentally, we want the result of alignment check to decide how to take the lock that protects the file size, so simply lifting O_APPEND treatment above those won't do. I suspect that in case of lock taken shared we need to redo alignment checks and treat "it became unaligned" as "unlock and redo it with lock taken exclusive".
BTW, xfs_break_layouts() having dropped and regained lock would invalidate the O_APPEND treatment in generic_write_checks() just prior (both in xfs_file_aio_write_checks())...
Al "really not fond of xfs_rw_ilock()" Viro...
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