On Tue, Aug 12, 2025 at 02:43:41PM +0200, cem@xxxxxxxxxx wrote:
> From: Carlos Maiolino <cem@xxxxxxxxxx>
>
> An user reported an inconsistency while mounting a V2 log filesystem
> with logbsize equals to the stripe unit being used (192k).
>
> The current validation algorithm for the log buffer size enforces the
> user to pass a power_of_2 value between [16k-256k].
> The manpage dictates the log buffer size must be a multiple of the log
> stripe unit, but doesn't specify it must be a power_of_2. Also, if
> logbsize is not specified at mount time, it will be set to
> max(32768, log_sunit), where log_sunit not necessarily is a power_of_2.
>
> It does seem to me then that logbsize being a power_of_2 constraint must
> be relaxed if there is a configured log stripe unit, so this patch
> updates the logbsize validation logic to ensure that:
>
> - It can only be set to a specific range [16k-256k]
>
> - Will be aligned to log stripe unit when the latter is set,
> and will be at least the same size as the log stripe unit.
>
> - Enforce it to be power_of_2 aligned when log stripe unit is not set.
>
> This is achieved by factoring out the logbsize validation to a separated
> function to avoid a big chain of if conditionals
>
> While at it, update m_logbufs and m_logbsize conditionals in
> xfs_fs_validate_params from:
> (x != -1 && x != 0) to (x > 0)
>
> Signed-off-by: Carlos Maiolino <cmaiolino@xxxxxxxxxx>
> ---
>
> I am sending this as a RFC because although I did some basic testing,
> xfstests is still running, so I can't tell yet if it will fail on some configuration even though I am not expecting it to.
Heheh, how did that go?
> fs/xfs/xfs_super.c | 57 ++++++++++++++++++++++++++++++++--------------
> 1 file changed, 40 insertions(+), 17 deletions(-)
>
> diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
> index bb0a82635a77..38d3d8a0b026 100644
> --- a/fs/xfs/xfs_super.c
> +++ b/fs/xfs/xfs_super.c
> @@ -1059,6 +1059,29 @@ xfs_fs_unfreeze(
> return 0;
> }
>
> +STATIC int
> +xfs_validate_logbsize(
> + struct xfs_mount *mp)
> +{
> + int logbsize = mp->m_logbsize;
> + uint32_t logsunit = mp->m_sb.sb_logsunit;
Why not access the fields directly instead of going through convenience
variables?
> + if (logsunit > 1) {
> + if (logbsize < logsunit ||
> + logbsize % logsunit) {
> + xfs_warn(mp,
> + "logbuf size must be a multiple of the log stripe unit");
> + return -EINVAL;
> + }
> + } else {
> + if (!is_power_of_2(logbsize)) {
> + xfs_warn(mp,
Odd indenting here ^^^
> + "invalid logbufsize: %d [not a power of 2]", logbsize);
> + return -EINVAL;
> + }
> + }
> + return 0;
> +}
> /*
> * This function fills in xfs_mount_t fields based on mount args.
> * Note: the superblock _has_ now been read in.
> @@ -1067,16 +1090,13 @@ STATIC int
> xfs_finish_flags(
> struct xfs_mount *mp)
> {
> - /* Fail a mount where the logbuf is smaller than the log stripe */
> if (xfs_has_logv2(mp)) {
> - if (mp->m_logbsize <= 0 &&
> - mp->m_sb.sb_logsunit > XLOG_BIG_RECORD_BSIZE) {
> - mp->m_logbsize = mp->m_sb.sb_logsunit;
> - } else if (mp->m_logbsize > 0 &&
> - mp->m_logbsize < mp->m_sb.sb_logsunit) {
> - xfs_warn(mp,
> - "logbuf size must be greater than or equal to log stripe size");
> - return -EINVAL;
> + if (mp->m_logbsize > 0) {
> + if (xfs_validate_logbsize(mp))
> + return -EINVAL;
If you're going to have xfs_validate_logbsize return an errno, then
capture it and return that, instead squashing them all to EINVAL.
AFAICT it's no big deal to have non-power-of-two log buffers, right?
I *think* everything looks ok, but I'm no expert in the bottom levels of
the xfs logging code. :/
--D
> + } else {
> + if (mp->m_sb.sb_logsunit > XLOG_BIG_RECORD_BSIZE)
> + mp->m_logbsize = mp->m_sb.sb_logsunit;
> }
> } else {
> /* Fail a mount if the logbuf is larger than 32K */
> @@ -1628,8 +1648,7 @@ xfs_fs_validate_params(
> return -EINVAL;
> }
>
> - if (mp->m_logbufs != -1 &&
> - mp->m_logbufs != 0 &&
> + if (mp->m_logbufs > 0 &&
> (mp->m_logbufs < XLOG_MIN_ICLOGS ||
> mp->m_logbufs > XLOG_MAX_ICLOGS)) {
> xfs_warn(mp, "invalid logbufs value: %d [not %d-%d]",
> @@ -1637,14 +1656,18 @@ xfs_fs_validate_params(
> return -EINVAL;
> }
>
> - if (mp->m_logbsize != -1 &&
> - mp->m_logbsize != 0 &&
> + /*
> + * We have not yet read the superblock, so we can't check against
> + * logsunit here.
> + */
> + if (mp->m_logbsize > 0 &&
> (mp->m_logbsize < XLOG_MIN_RECORD_BSIZE ||
> - mp->m_logbsize > XLOG_MAX_RECORD_BSIZE ||
> - !is_power_of_2(mp->m_logbsize))) {
> + mp->m_logbsize > XLOG_MAX_RECORD_BSIZE)) {
> xfs_warn(mp,
> - "invalid logbufsize: %d [not 16k,32k,64k,128k or 256k]",
> - mp->m_logbsize);
> + "invalid logbufsize: %d [not in range %dk-%dk]",
> + mp->m_logbsize,
> + (XLOG_MIN_RECORD_BSIZE/1024),
> + (XLOG_MAX_RECORD_BSIZE/1024));
> return -EINVAL;
> }
>
> --
> 2.50.1
>
>
