fs/xfs/libxfs/xfs_log_rlimit.c

Source file repositories/reference/linux-study-clean/fs/xfs/libxfs/xfs_log_rlimit.c

File Facts

System
Linux kernel
Corpus path
fs/xfs/libxfs/xfs_log_rlimit.c
Extension
.c
Size
8268 bytes
Lines
252
Domain
Core OS
Bucket
VFS And Filesystem Core
Inferred role
Core OS: implementation source
Status
source implementation candidate

Why This File Exists

Core operating-system implementation surface: boot, tasks, memory, VFS, syscall-facing interfaces, synchronization, credentials, and isolation.

Dependency Surface

Detected Declarations

Annotated Snippet

if (log_space < tmp) {
			log_space = tmp;
			*max_resp = *resp;		/* struct copy */
		}
	}

	if (attr_space > log_space) {
		*max_resp = resv.tr_attrsetm;	/* struct copy */
		max_resp->tr_logres = attr_space;
	}
	trace_xfs_log_get_max_trans_res(mp, max_resp);
}

/*
 * Calculate the minimum valid log size for the given superblock configuration.
 * Used to calculate the minimum log size at mkfs time, and to determine if
 * the log is large enough or not at mount time. Returns the minimum size in
 * filesystem block size units.
 */
int
xfs_log_calc_minimum_size(
	struct xfs_mount	*mp)
{
	struct xfs_trans_res	tres = {0};
	int			max_logres;
	int			min_logblks = 0;
	int			lsunit = 0;

	xfs_log_get_max_trans_res(mp, &tres);

	max_logres = xfs_log_calc_unit_res(mp, tres.tr_logres);
	if (tres.tr_logcount > 1)
		max_logres *= tres.tr_logcount;

	if (xfs_has_logv2(mp) && mp->m_sb.sb_logsunit > 1)
		lsunit = BTOBB(mp->m_sb.sb_logsunit);

	/*
	 * Two factors should be taken into account for calculating the minimum
	 * log space.
	 * 1) The fundamental limitation is that no single transaction can be
	 *    larger than half size of the log.
	 *
	 *    From mkfs.xfs, this is considered by the XFS_MIN_LOG_FACTOR
	 *    define, which is set to 3. That means we can definitely fit
	 *    maximally sized 2 transactions in the log. We'll use this same
	 *    value here.
	 *
	 * 2) If the lsunit option is specified, a transaction requires 2 LSU
	 *    for the reservation because there are two log writes that can
	 *    require padding - the transaction data and the commit record which
	 *    are written separately and both can require padding to the LSU.
	 *    Consider that we can have an active CIL reservation holding 2*LSU,
	 *    but the CIL is not over a push threshold, in this case, if we
	 *    don't have enough log space for at one new transaction, which
	 *    includes another 2*LSU in the reservation, we will run into dead
	 *    loop situation in log space grant procedure. i.e.
	 *    xlog_grant_head_wait().
	 *
	 *    Hence the log size needs to be able to contain two maximally sized
	 *    and padded transactions, which is (2 * (2 * LSU + maxlres)).
	 *
	 * Also, the log size should be a multiple of the log stripe unit, round
	 * it up to lsunit boundary if lsunit is specified.
	 */
	if (lsunit) {
		min_logblks = roundup_64(BTOBB(max_logres), lsunit) +
			      2 * lsunit;
	} else
		min_logblks = BTOBB(max_logres) + 2 * BBSIZE;
	min_logblks *= XFS_MIN_LOG_FACTOR;

	return XFS_BB_TO_FSB(mp, min_logblks);
}

Annotation

Implementation Notes