libxfs/xfs_log_rlimit.c

   1 /*
   2  * Copyright (c) 2013 Jie Liu.
   3  * All Rights Reserved.
   4  *
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU General Public License as
   7  * published by the Free Software Foundation.
   8  *
   9  * This program is distributed in the hope that it would be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write the Free Software Foundation,
  16  * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  17  */
  18 #include <xfs.h>
  19
  20 /*
  21  * Calculate the maximum length in bytes that would be required for a local
  22  * attribute value as large attributes out of line are not logged.
  23  */
  24 STATIC int
  25 xfs_log_calc_max_attrsetm_res(
  26         struct xfs_mount        *mp)
  27 {
  28         int                     size;
  29         int                     nblks;
  30
  31         size = xfs_attr_leaf_entsize_local_max(mp->m_attr_geo->blksize) -
  32                MAXNAMELEN - 1;
  33         nblks = XFS_DAENTER_SPACE_RES(mp, XFS_ATTR_FORK);
  34         nblks += XFS_B_TO_FSB(mp, size);
  35         nblks += XFS_NEXTENTADD_SPACE_RES(mp, size, XFS_ATTR_FORK);
  36
  37         return  M_RES(mp)->tr_attrsetm.tr_logres +
  38                 M_RES(mp)->tr_attrsetrt.tr_logres * nblks;
  39 }
  40
  41 /*
  42  * Iterate over the log space reservation table to figure out and return
  43  * the maximum one in terms of the pre-calculated values which were done
  44  * at mount time.
  45  */
  46 STATIC void
  47 xfs_log_get_max_trans_res(
  48         struct xfs_mount        *mp,
  49         struct xfs_trans_res    *max_resp)
  50 {
  51         struct xfs_trans_res    *resp;
  52         struct xfs_trans_res    *end_resp;
  53         int                     log_space = 0;
  54         int                     attr_space;
  55
  56         attr_space = xfs_log_calc_max_attrsetm_res(mp);
  57
  58         resp = (struct xfs_trans_res *)M_RES(mp);
  59         end_resp = (struct xfs_trans_res *)(M_RES(mp) + 1);
  60         for (; resp < end_resp; resp++) {
  61                 int             tmp = resp->tr_logcount > 1 ?
  62                                       resp->tr_logres * resp->tr_logcount :
  63                                       resp->tr_logres;
  64                 if (log_space < tmp) {
  65                         log_space = tmp;
  66                         *max_resp = *resp;              /* struct copy */
  67                 }
  68         }
  69
  70         if (attr_space > log_space) {
  71                 *max_resp = M_RES(mp)->tr_attrsetm;     /* struct copy */
  72                 max_resp->tr_logres = attr_space;
  73         }
  74 }
  75
  76 /*
  77  * Calculate the minimum valid log size for the given superblock configuration.
  78  * Used to calculate the minimum log size at mkfs time, and to determine if
  79  * the log is large enough or not at mount time. Returns the minimum size in
  80  * filesystem block size units.
  81  */
  82 int
  83 xfs_log_calc_minimum_size(
  84         struct xfs_mount        *mp)
  85 {
  86         struct xfs_trans_res    tres = {0};
  87         int                     max_logres;
  88         int                     min_logblks = 0;
  89         int                     lsunit = 0;
  90
  91         xfs_log_get_max_trans_res(mp, &tres);
  92
  93         max_logres = xfs_log_calc_unit_res(mp, tres.tr_logres);
  94         if (tres.tr_logcount > 1)
  95                 max_logres *= tres.tr_logcount;
  96
  97         if (xfs_sb_version_haslogv2(&mp->m_sb) && mp->m_sb.sb_logsunit > 1)
  98                 lsunit = BTOBB(mp->m_sb.sb_logsunit);
  99
 100         /*
 101          * Two factors should be taken into account for calculating the minimum
 102          * log space.
 103          * 1) The fundamental limitation is that no single transaction can be
 104          *    larger than half size of the log.
 105          *
 106          *    From mkfs.xfs, this is considered by the XFS_MIN_LOG_FACTOR
 107          *    define, which is set to 3. That means we can definitely fit
 108          *    maximally sized 2 transactions in the log. We'll use this same
 109          *    value here.
 110          *
 111          * 2) If the lsunit option is specified, a transaction requires 2 LSU
 112          *    for the reservation because there are two log writes that can
 113          *    require padding - the transaction data and the commit record which
 114          *    are written separately and both can require padding to the LSU.
 115          *    Consider that we can have an active CIL reservation holding 2*LSU,
 116          *    but the CIL is not over a push threshold, in this case, if we
 117          *    don't have enough log space for at one new transaction, which
 118          *    includes another 2*LSU in the reservation, we will run into dead
 119          *    loop situation in log space grant procedure. i.e.
 120          *    xlog_grant_head_wait().
 121          *
 122          *    Hence the log size needs to be able to contain two maximally sized
 123          *    and padded transactions, which is (2 * (2 * LSU + maxlres)).
 124          *
 125          * Also, the log size should be a multiple of the log stripe unit, round
 126          * it up to lsunit boundary if lsunit is specified.
 127          */
 128         if (lsunit) {
 129                 min_logblks = roundup_64(BTOBB(max_logres), lsunit) +
 130                               2 * lsunit;
 131         } else
 132                 min_logblks = BTOBB(max_logres) + 2 * BBSIZE;
 133         min_logblks *= XFS_MIN_LOG_FACTOR;
 134
 135         return XFS_BB_TO_FSB(mp, min_logblks);
 136 }