On Mon, Dec 19, 2011 at 02:03:40AM +0000, Al Viro wrote: > OK, I'm definitely missing something. The very first thing > xfs_file_aio_write_checks() does is > xfs_rw_ilock(ip, XFS_ILOCK_EXCL); > which really makes me wonder how the hell does that manage to avoid an > instant deadlock in case of call via xfs_file_buffered_aio_write() > where we have: > struct address_space *mapping = file->f_mapping; > struct inode *inode = mapping->host; > struct xfs_inode *ip = XFS_I(inode); > *iolock = XFS_IOLOCK_EXCL; > xfs_rw_ilock(ip, *iolock); > ret = xfs_file_aio_write_checks(file, &pos, &count, new_size, iolock); > which leads to > struct inode *inode = file->f_mapping->host; > struct xfs_inode *ip = XFS_I(inode); > (IOW, inode and ip are the same as in the caller) followed by > xfs_rw_ilock(ip, XFS_ILOCK_EXCL); > and with both xfs_rw_ilock() calls turning into > mutex_lock(&VFS_I(ip)->i_mutex); > xfs_ilock(ip, XFS_ILOCK_EXCL); > we ought to deadlock on that i_mutex. What am I missing and how do we manage > to survive that? Arrrgh... OK, I see... What I missed is that XFS_IOLOCK_EXCL is not XFS_ILOCK_EXCL. Nice naming, that... -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>