From: "Darrick J. Wong" darrick.wong@oracle.com
commit 78bba5c812cc651cee51b64b786be926ab7fe2a9 upstream.
While QAing the new xfs_repair quotacheck code, I uncovered a quota corruption bug resulting from a bad interaction between dquot buffer initialization and quotacheck. The bug can be reproduced with the following sequence:
# mkfs.xfs -f /dev/sdf # mount /dev/sdf /opt -o usrquota # su nobody -s /bin/bash -c 'touch /opt/barf' # sync # xfs_quota -x -c 'report -ahi' /opt User quota on /opt (/dev/sdf) Inodes User ID Used Soft Hard Warn/Grace ---------- --------------------------------- root 3 0 0 00 [------] nobody 1 0 0 00 [------]
# xfs_io -x -c 'shutdown' /opt # umount /opt # mount /dev/sdf /opt -o usrquota # touch /opt/man2 # xfs_quota -x -c 'report -ahi' /opt User quota on /opt (/dev/sdf) Inodes User ID Used Soft Hard Warn/Grace ---------- --------------------------------- root 1 0 0 00 [------] nobody 1 0 0 00 [------]
# umount /opt
Notice how the initial quotacheck set the root dquot icount to 3 (rootino, rbmino, rsumino), but after shutdown -> remount -> recovery, xfs_quota reports that the root dquot has only 1 icount. We haven't deleted anything from the filesystem, which means that quota is now under-counting. This behavior is not limited to icount or the root dquot, but this is the shortest reproducer.
I traced the cause of this discrepancy to the way that we handle ondisk dquot updates during quotacheck vs. regular fs activity. Normally, when we allocate a disk block for a dquot, we log the buffer as a regular (dquot) buffer. Subsequent updates to the dquots backed by that block are done via separate dquot log item updates, which means that they depend on the logged buffer update being written to disk before the dquot items. Because individual dquots have their own LSN fields, that initial dquot buffer must always be recovered.
However, the story changes for quotacheck, which can cause dquot block allocations but persists the final dquot counter values via a delwri list. Because recovery doesn't gate dquot buffer replay on an LSN, this means that the initial dquot buffer can be replayed over the (newer) contents that were delwritten at the end of quotacheck. In effect, this re-initializes the dquot counters after they've been updated. If the log does not contain any other dquot items to recover, the obsolete dquot contents will not be corrected by log recovery.
Because quotacheck uses a transaction to log the setting of the CHKD flags in the superblock, we skip quotacheck during the second mount call, which allows the incorrect icount to remain.
Fix this by changing the ondisk dquot initialization function to use ordered buffers to write out fresh dquot blocks if it detects that we're running quotacheck. If the system goes down before quotacheck can complete, the CHKD flags will not be set in the superblock and the next mount will run quotacheck again, which can fix uninitialized dquot buffers. This requires amending the defer code to maintaine ordered buffer state across defer rolls for the sake of the dquot allocation code.
For regular operations we preserve the current behavior since the dquot items require properly initialized ondisk dquot records.
Signed-off-by: Darrick J. Wong darrick.wong@oracle.com Reviewed-by: Brian Foster bfoster@redhat.com Reviewed-by: Christoph Hellwig hch@lst.de Acked-by: Darrick J. Wong djwong@kernel.org Signed-off-by: Chandan Babu R chandan.babu@oracle.com --- fs/xfs/libxfs/xfs_defer.c | 10 ++++++- fs/xfs/xfs_dquot.c | 56 ++++++++++++++++++++++++++++++--------- 2 files changed, 52 insertions(+), 14 deletions(-)
diff --git a/fs/xfs/libxfs/xfs_defer.c b/fs/xfs/libxfs/xfs_defer.c index 22557527cfdb..8cc3faa62404 100644 --- a/fs/xfs/libxfs/xfs_defer.c +++ b/fs/xfs/libxfs/xfs_defer.c @@ -234,10 +234,13 @@ xfs_defer_trans_roll( struct xfs_log_item *lip; struct xfs_buf *bplist[XFS_DEFER_OPS_NR_BUFS]; struct xfs_inode *iplist[XFS_DEFER_OPS_NR_INODES]; + unsigned int ordered = 0; /* bitmap */ int bpcount = 0, ipcount = 0; int i; int error;
+ BUILD_BUG_ON(NBBY * sizeof(ordered) < XFS_DEFER_OPS_NR_BUFS); + list_for_each_entry(lip, &tp->t_items, li_trans) { switch (lip->li_type) { case XFS_LI_BUF: @@ -248,7 +251,10 @@ xfs_defer_trans_roll( ASSERT(0); return -EFSCORRUPTED; } - xfs_trans_dirty_buf(tp, bli->bli_buf); + if (bli->bli_flags & XFS_BLI_ORDERED) + ordered |= (1U << bpcount); + else + xfs_trans_dirty_buf(tp, bli->bli_buf); bplist[bpcount++] = bli->bli_buf; } break; @@ -289,6 +295,8 @@ xfs_defer_trans_roll( /* Rejoin the buffers and dirty them so the log moves forward. */ for (i = 0; i < bpcount; i++) { xfs_trans_bjoin(tp, bplist[i]); + if (ordered & (1U << i)) + xfs_trans_ordered_buf(tp, bplist[i]); xfs_trans_bhold(tp, bplist[i]); }
diff --git a/fs/xfs/xfs_dquot.c b/fs/xfs/xfs_dquot.c index 9596b86e7de9..6231b155e7f3 100644 --- a/fs/xfs/xfs_dquot.c +++ b/fs/xfs/xfs_dquot.c @@ -205,16 +205,18 @@ xfs_qm_adjust_dqtimers( */ STATIC void xfs_qm_init_dquot_blk( - xfs_trans_t *tp, - xfs_mount_t *mp, - xfs_dqid_t id, - uint type, - xfs_buf_t *bp) + struct xfs_trans *tp, + struct xfs_mount *mp, + xfs_dqid_t id, + uint type, + struct xfs_buf *bp) { struct xfs_quotainfo *q = mp->m_quotainfo; - xfs_dqblk_t *d; - xfs_dqid_t curid; - int i; + struct xfs_dqblk *d; + xfs_dqid_t curid; + unsigned int qflag; + unsigned int blftype; + int i;
ASSERT(tp); ASSERT(xfs_buf_islocked(bp)); @@ -238,11 +240,39 @@ xfs_qm_init_dquot_blk( } }
- xfs_trans_dquot_buf(tp, bp, - (type & XFS_DQ_USER ? XFS_BLF_UDQUOT_BUF : - ((type & XFS_DQ_PROJ) ? XFS_BLF_PDQUOT_BUF : - XFS_BLF_GDQUOT_BUF))); - xfs_trans_log_buf(tp, bp, 0, BBTOB(q->qi_dqchunklen) - 1); + if (type & XFS_DQ_USER) { + qflag = XFS_UQUOTA_CHKD; + blftype = XFS_BLF_UDQUOT_BUF; + } else if (type & XFS_DQ_PROJ) { + qflag = XFS_PQUOTA_CHKD; + blftype = XFS_BLF_PDQUOT_BUF; + } else { + qflag = XFS_GQUOTA_CHKD; + blftype = XFS_BLF_GDQUOT_BUF; + } + + xfs_trans_dquot_buf(tp, bp, blftype); + + /* + * quotacheck uses delayed writes to update all the dquots on disk in an + * efficient manner instead of logging the individual dquot changes as + * they are made. However if we log the buffer allocated here and crash + * after quotacheck while the logged initialisation is still in the + * active region of the log, log recovery can replay the dquot buffer + * initialisation over the top of the checked dquots and corrupt quota + * accounting. + * + * To avoid this problem, quotacheck cannot log the initialised buffer. + * We must still dirty the buffer and write it back before the + * allocation transaction clears the log. Therefore, mark the buffer as + * ordered instead of logging it directly. This is safe for quotacheck + * because it detects and repairs allocated but initialized dquot blocks + * in the quota inodes. + */ + if (!(mp->m_qflags & qflag)) + xfs_trans_ordered_buf(tp, bp); + else + xfs_trans_log_buf(tp, bp, 0, BBTOB(q->qi_dqchunklen) - 1); }
/*