Author: delphij Date: Sat Nov 30 20:06:53 2019 New Revision: 355247 URL: https://svnweb.freebsd.org/changeset/base/355247
Log: Reduce disk write load in /usr/libexec/save-entropy. Before this commit, the save-entropy script rotates entropy files like logs. This involves creating a new file that holds the entropy and renaming of all existing entropy files. However, the entropy data do not really need to be kept in a particular order, and replacing the oldest file is sufficient. This commit replaces the rotation with a scan in the [1..entropy_save_num] space that finds the first empty slot, or the slot of the oldest file, and writes entropy into that slot. This also fixes an issue that prevents save-entropy from saving any entropy when there is one non-regular file in any slot as a side effect. Based on an earlier patch from peterj@. PR: 134225 Reported by: peterj Reviewed by: csprng (cem, markm) MFC after: 2 weeks Differential Revision: https://reviews.freebsd.org/D22612 Modified: head/libexec/save-entropy/save-entropy.sh Modified: head/libexec/save-entropy/save-entropy.sh ============================================================================== --- head/libexec/save-entropy/save-entropy.sh Sat Nov 30 20:04:40 2019 (r355246) +++ head/libexec/save-entropy/save-entropy.sh Sat Nov 30 20:06:53 2019 (r355247) @@ -71,26 +71,63 @@ cd "${entropy_dir}" || { for f in saved-entropy.*; do case "${f}" in saved-entropy.\*) continue ;; esac # No files match - [ ${f#saved-entropy\.} -ge ${entropy_save_num} ] && unlink ${f} + [ ${f#saved-entropy\.} -gt ${entropy_save_num} ] && unlink ${f} done -umask 377 +umask 177 -n=$(( ${entropy_save_num} - 1 )) -while [ ${n} -ge 1 ]; do - if [ -f "saved-entropy.${n}" ]; then - mv "saved-entropy.${n}" "saved-entropy.$(( ${n} + 1 ))" - elif [ -e "saved-entropy.${n}" -o -L "saved-entropy.${n}" ]; then +# Scan slots [1..$entropy_save_num), picking an empty slot or the oldest +# existing file if no empty slot was available. +# +# 1. Find out the first regular file or empty slot (and its serial number) +# +n=1 +while [ ${n} -le ${entropy_save_num} ]; do + save_file="saved-entropy.${n}" + if [ ! -e "${save_file}" -o -f "${save_file}" ]; then + break + else logger -is -t "$0" \ - "${entropy_dir}/saved-entropy.${n}" is not a regular file, and so \ - it will not be rotated. Entropy file rotation is aborted. - exit 1 + "${save_file}" is not a regular file, skipped. fi - n=$(( ${n} - 1 )) + n=$(( ${n} + 1 )) done +# +# 2. Start from (serial number + 1), and check if the slot is empty +# or is an older regular file, update save_file pointer in either +# case, and break early if we found an empty slot. +# +if [ -f ${save_file} ]; then + n=$(( ${n} + 1 )) + while [ ${n} -le ${entropy_save_num} ]; do + next_file=saved-entropy.${n} + if [ -f "${next_file}" ]; then + [ "${next_file}" -ot "${save_file}" ] && \ + save_file="${next_file}" + elif [ ! -e "${next_file}" ]; then + save_file="${next_file}" + break + else + logger -is -t "$0" \ + "${next_file}" is not a regular file, skipped. + fi + n=$(( ${n} + 1 )) + done +fi +# +# 3. Check if the pointer we have in hand is really a regular file or +# an empty slot, and bail out as that means there is no available slot. +# +if [ -e "${save_file}" -a ! -f "${save_file}" ]; then + logger -is -t "$0" \ + No available slot in "${entropy_dir}", save entropy is aborted. + exit 1 +fi -dd if=/dev/random of=saved-entropy.1 bs=${entropy_save_sz} count=1 2>/dev/null -chflags nodump saved-entropy.1 2>/dev/null || : -fsync saved-entropy.1 "." +# Save entropy to the selected slot. +chmod 600 "${save_file}" 2>/dev/null || : +dd if=/dev/random of="${save_file}" bs=${entropy_save_sz} count=1 2>/dev/null +chflags nodump "${save_file}" 2>/dev/null || : +fsync "${save_file}" "." exit 0 _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
