On Fri, Jun 16, 2017 at 12:44:33PM -0400, Brian Foster wrote: > Create a debug mode only sysfs option to force pin the tail of the > log. This option can be used by test infrastructure to induce head > behind tail conditions. Specifically, this is intended to be used by > xfstests to reproduce log recovery problems after failed/corrupted > log writes overwrite the last good tail LSN in the log. > > When enabled, AIL push attempts see every log item on the AIL in the > pinned state. This stalls metadata writeback and thus prevents the > current tail of the log from moving forward. When disabled, > subsequent AIL pushes observe the log items in their appropriate > state and filesystem operation continues as normal. > > Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx> Looks ok enough to test... Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx> --D > --- > > Hi all, > > This patch is a supporting patch for an xfstests test I'm about to post > that pins the tail of the log in order to reproduce the log recovery > problem that appears to be the root of the problem in this[1] thread. > That is the primary motivation for the patch and so should probably be > reviewed with that context. IOW, if there's a better way to reproduce > the problem in the test without the need for kernel support, I'm happy > to drop this. Thoughts, reviews, flames appreciated. > > Brian > > [1] http://www.spinics.net/lists/linux-xfs/msg07499.html > > fs/xfs/xfs_log_priv.h | 2 ++ > fs/xfs/xfs_sysfs.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++ > fs/xfs/xfs_trans_ail.c | 20 +++++++++++++++++++- > 3 files changed, 67 insertions(+), 1 deletion(-) > > diff --git a/fs/xfs/xfs_log_priv.h b/fs/xfs/xfs_log_priv.h > index c2604a5..bfbfde12 100644 > --- a/fs/xfs/xfs_log_priv.h > +++ b/fs/xfs/xfs_log_priv.h > @@ -413,6 +413,8 @@ struct xlog { > void *l_iclog_bak[XLOG_MAX_ICLOGS]; > /* log record crc error injection factor */ > uint32_t l_badcrc_factor; > + /* force pin the log tail */ > + bool l_pin_tail; > #endif > /* log recovery lsn tracking (for buffer submission */ > xfs_lsn_t l_recovery_lsn; > diff --git a/fs/xfs/xfs_sysfs.c b/fs/xfs/xfs_sysfs.c > index ec6e0e2..b86148a 100644 > --- a/fs/xfs/xfs_sysfs.c > +++ b/fs/xfs/xfs_sysfs.c > @@ -378,6 +378,51 @@ log_badcrc_factor_show( > } > > XFS_SYSFS_ATTR_RW(log_badcrc_factor); > + > +/* > + * DEBUG mode flag to force pin the tail of the log. Used from test > + * infrastructure to manufacture head-behind-tail conditions. DO NOT USE > + * DIRECTLY. This will lock up the fs! > + * > + * When this option is enabled, all log items present in the AIL are emulated as > + * being in the pinned state until the option is disabled. Once disabled, log > + * items return to their natural state and fs operation continues as normal. > + */ > +STATIC ssize_t > +log_pin_tail_store( > + struct kobject *kobject, > + const char *buf, > + size_t count) > +{ > + struct xlog *log = to_xlog(kobject); > + int ret; > + int val; > + > + ret = kstrtoint(buf, 0, &val); > + if (ret) > + return ret; > + > + if (val == 1) > + log->l_pin_tail = true; > + else if (val == 0) > + log->l_pin_tail = false; > + else > + return -EINVAL; > + > + return count; > +} > + > +STATIC ssize_t > +log_pin_tail_show( > + struct kobject *kobject, > + char *buf) > +{ > + struct xlog *log = to_xlog(kobject); > + > + return snprintf(buf, PAGE_SIZE, "%d\n", log->l_pin_tail ? 1 : 0); > +} > +XFS_SYSFS_ATTR_RW(log_pin_tail); > + > #endif /* DEBUG */ > > static struct attribute *xfs_log_attrs[] = { > @@ -387,6 +432,7 @@ static struct attribute *xfs_log_attrs[] = { > ATTR_LIST(write_grant_head), > #ifdef DEBUG > ATTR_LIST(log_badcrc_factor), > + ATTR_LIST(log_pin_tail), > #endif > NULL, > }; > diff --git a/fs/xfs/xfs_trans_ail.c b/fs/xfs/xfs_trans_ail.c > index 9056c0f..c901e61 100644 > --- a/fs/xfs/xfs_trans_ail.c > +++ b/fs/xfs/xfs_trans_ail.c > @@ -27,6 +27,7 @@ > #include "xfs_trace.h" > #include "xfs_error.h" > #include "xfs_log.h" > +#include "xfs_log_priv.h" > > #ifdef DEBUG > /* > @@ -325,6 +326,23 @@ xfs_ail_delete( > xfs_trans_ail_cursor_clear(ailp, lip); > } > > +static inline uint > +xfsaild_push_item( > + struct xfs_ail *ailp, > + struct xfs_log_item *lip) > +{ > +#ifdef DEBUG > + /* > + * If tail pinning is enabled, skip the push and track all items as > + * pinned to force pin the log tail. This helps induce head-behind-tail > + * conditions. > + */ > + if (ailp->xa_mount->m_log->l_pin_tail) > + return XFS_ITEM_PINNED; > +#endif > + return lip->li_ops->iop_push(lip, &ailp->xa_buf_list); > +} > + > static long > xfsaild_push( > struct xfs_ail *ailp) > @@ -382,7 +400,7 @@ xfsaild_push( > * rely on the AIL cursor implementation to be able to deal with > * the dropped lock. > */ > - lock_result = lip->li_ops->iop_push(lip, &ailp->xa_buf_list); > + lock_result = xfsaild_push_item(ailp, lip); > switch (lock_result) { > case XFS_ITEM_SUCCESS: > XFS_STATS_INC(mp, xs_push_ail_success); > -- > 2.7.5 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
