Monorepo for Aesthetic.Computer
aesthetic.computer
fix(native): BLKFLSBUF + drop_caches to release nvme after lazy unmount
The install-to-HD was failing because MNT_DETACH (lazy unmount) removes
the mount from the namespace but the kernel VFS holds block device
references via cached dentries/inodes/superblock. BLKRRPART and mkfs
both fail with EBUSY because the block layer still considers the device
exclusively held.
Fix: after unmounting, flush the block device buffer cache via BLKFLSBUF
ioctl on both the partition and whole disk, then drop all page/dentry/
inode caches before attempting sfdisk or mkfs. Also increase mkfs retry
count to 5 with BLKFLSBUF flush between each attempt.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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fedac/native/src/ac-native.c
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fedac/native/src/ac-native.c
···
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ac_log("[install] force_unmount_disk(%s) released %d mounts\n",
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parent_blk, n_unmounted);
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sync();
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-
usleep(500000);
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+
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// CRITICAL: After MNT_DETACH (lazy unmount), the kernel
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// VFS still holds block device references from cached
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// dentries/inodes/superblock. We MUST flush buffer cache
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// on both the partition and whole disk via BLKFLSBUF,
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// then drop page caches, before the block layer will
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// release its exclusive hold. Without this, BLKRRPART
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// and mkfs both fail with EBUSY.
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{
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// Flush buffer cache on partition
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int pfd = open(devpath, O_RDONLY | O_CLOEXEC);
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if (pfd >= 0) {
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ioctl(pfd, BLKFLSBUF);
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close(pfd);
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ac_log("[install] BLKFLSBUF on %s: ok\n", devpath);
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}
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// Flush buffer cache on whole disk
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char disk_dev[64];
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snprintf(disk_dev, sizeof(disk_dev), "/dev/%s", parent_blk);
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int dfd = open(disk_dev, O_RDONLY | O_CLOEXEC);
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if (dfd >= 0) {
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ioctl(dfd, BLKFLSBUF);
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close(dfd);
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ac_log("[install] BLKFLSBUF on %s: ok\n", disk_dev);
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}
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// Drop all page/dentry/inode caches
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system("echo 3 > /proc/sys/vm/drop_caches 2>/dev/null || true");
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sync();
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ac_log("[install] caches flushed + dropped\n");
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}
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usleep(1000000); // 1s settle after cache flush
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// Nuke the old filesystem signatures BEFORE sfdisk. This
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// is critical: the old Fedora ESP's FAT boot sector and
···
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"fi",
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DLOG, devpath, DLOG, DLOG, devpath, DLOG);
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system(rcmd);
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// Drop the kernel page cache so any lingering references
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// to the old filesystem's cached pages are released.
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// Aggressively flush block device buffer cache + page cache
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// to release the kernel's exclusive hold on the partition.
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{
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int pfd = open(devpath, O_RDONLY | O_CLOEXEC);
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if (pfd >= 0) { ioctl(pfd, BLKFLSBUF); close(pfd); }
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char disk_dev2[64];
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snprintf(disk_dev2, sizeof(disk_dev2), "/dev/%s", parent_blk);
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int dfd = open(disk_dev2, O_RDONLY | O_CLOEXEC);
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if (dfd >= 0) { ioctl(dfd, BLKFLSBUF); close(dfd); }
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}
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system("echo 3 > /proc/sys/vm/drop_caches 2>/dev/null || true");
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sync();
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ac_log("[install] pre-mkfs cache flush done\n");
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// Long settle — let the kernel + nvme driver fully release
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// the device. 3 seconds gives enough margin for the block
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// layer to quiesce after partx + wipefs.
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usleep(3000000);
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// the device. 5 seconds to be safe.
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usleep(5000000);
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// Reformat. Retry up to 3 times if mkfs fails — the
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// kernel sometimes needs multiple passes after a fresh
···
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fclose(mf);
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}
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}
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// Attempt 2 + 3 if needed
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for (int mkfs_try = 2; mkfs_try <= 3 && mkfs_exit != 0; mkfs_try++) {
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// Attempt 2–5 if needed (more retries with aggressive flush)
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for (int mkfs_try = 2; mkfs_try <= 5 && mkfs_exit != 0; mkfs_try++) {
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// Flush block device buffer cache before each retry
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{
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int pfd = open(devpath, O_RDONLY | O_CLOEXEC);
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if (pfd >= 0) { ioctl(pfd, BLKFLSBUF); close(pfd); }
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char dd2[64];
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snprintf(dd2, sizeof(dd2), "/dev/%s", parent_blk);
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int dfd = open(dd2, O_RDONLY | O_CLOEXEC);
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if (dfd >= 0) { ioctl(dfd, BLKFLSBUF); close(dfd); }
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}
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sync();
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system("echo 3 > /proc/sys/vm/drop_caches 2>/dev/null || true");
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usleep(2000000); // 2s settle between retries
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usleep(3000000); // 3s settle between retries
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snprintf(rcmd, sizeof(rcmd),
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"echo '--- mkfs attempt %d ---' >> %s; "
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"(mkfs.vfat -F 32 -n AC-NATIVE %s > %s 2>&1; rc=$?; "