The first 4 bytes of every basic block in the physical log is stamped with the current lsn. To support this mechanism, the log record header (first block of each new log record) contains space for the original first byte of each log record block before it is replaced with the lsn. The log record header has space for 32k worth of blocks. The version 2 log adds new extended record headers for each additional 32k worth of blocks beyond what is supported by the record header. The log record checksum incorporates the log record header, the extended headers and the record payload. xlog_cksum() checksums the extended headers based on log->l_iclog_heads, which specifies the number of extended headers in a log record based on the log buffer size mount option. The log buffer size is variable, however, and thus means the checksum can be calculated differently based on how a filesystem is mounted. This is problematic if a filesystem crashes and recovery occurs on a subsequent mount using a different log buffer size. For example, crash an active filesystem that is mounted with the default (32k) logbsize, attempt remount/recovery using '-o logbsize=64k' and the mount fails on or warns about log checksum failures. To avoid this problem, update xlog_cksum() to calculate the checksum based on the size of the log buffer according to the log record. The size is already included in the h_size field of the log record header and thus is available at log recovery time. Extended log record headers are also only written when the log record is large enough to require them. This makes checksum calculation of log records consistent with the extended record header mechanism as well as how on-disk records are checksummed with various log buffer size mount options. Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx> --- Hi all, This is a bit of a behavior oddity I ran into while messing around with the torn log write handling stuff I'm currently working on. I've posted an xfstests test that reproduces the problem here: http://thread.gmane.org/gmane.comp.file-systems.fstests/933 Brian fs/xfs/xfs_log.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c index 08d4fe4..61ce3c0 100644 --- a/fs/xfs/xfs_log.c +++ b/fs/xfs/xfs_log.c @@ -1652,8 +1652,13 @@ xlog_cksum( if (xfs_sb_version_haslogv2(&log->l_mp->m_sb)) { union xlog_in_core2 *xhdr = (union xlog_in_core2 *)rhead; int i; + int xheads; - for (i = 1; i < log->l_iclog_heads; i++) { + xheads = size / XLOG_HEADER_CYCLE_SIZE; + if (size % XLOG_HEADER_CYCLE_SIZE) + xheads++; + + for (i = 1; i < xheads; i++) { crc = crc32c(crc, &xhdr[i].hic_xheader, sizeof(struct xlog_rec_ext_header)); } -- 2.1.0 _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
