有趣的是，当我断开具有以只读模式（使用mount -o ro）安装的文件系统的 USB 闪存驱动器时，会出现此错误消息。
当文件系统以只读方式挂载时，为什么错误消息中会出现“写入”？这是 ext4 实现中的错误吗？
更多背景信息（它是 sde2）：
[ 227.821431] usb 1-1.4: USB disconnect, device number 3
[ 227.840961] sde: detected capacity change from 15773696 to 0
[ 227.841037] EXT4-fs (sde2): shut down requested (2)
[ 227.842219] Aborting journal on device sde2-8.
[ 227.843374] Buffer I/O error on dev sde2, logical block 9, lost sync page write
[ 227.844525] JBD2: I/O error when updating journal superblock for sde2-8.
[ 227.850957] I/O error, dev loop0, sector 8 op 0x0:(READ) flags 0x800 phys_seg 1 prio class 2
[ 227.892421] I/O error, dev loop0, sector 32776 op 0x0:(READ) flags 0x800 phys_seg 1 prio class 2
[ 227.899278] I/O error, dev loop0, sector 8 op 0x0:(READ) flags 0x800 phys_seg 1 prio class 2
[ 227.902603] I/O error, dev loop0, sector 32776 op 0x0:(READ) flags 0x800 phys_seg 1 prio class 2
[ 227.908819] I/O error, dev loop0, sector 8 op 0x0:(READ) flags 0x800 phys_seg 1 prio class 2
[ 227.911836] I/O error, dev loop0, sector 32776 op 0x0:(READ) flags 0x800 phys_seg 1 prio class 2
[ 227.917958] I/O error, dev loop0, sector 8 op 0x0:(READ) flags 0x800 phys_seg 1 prio class 2
[ 227.956534] I/O error, dev loop0, sector 32776 op 0x0:(READ) flags 0x800 phys_seg 1 prio class 2
[ 227.962874] I/O error, dev loop0, sector 8 op 0x0:(READ) flags 0x800 phys_seg 1 prio class 2
[ 227.965975] I/O error, dev loop0, sector 32776 op 0x0:(READ) flags 0x800 phys_seg 1 prio class 2
[ 232.880689] blk_print_req_error: 465 callbacks suppressed
[ 232.880693] I/O error, dev loop0, sector 32776 op 0x0:(READ) flags 0x800 phys_seg 1 prio class 2
[ 232.887171] I/O error, dev loop0, sector 8 op 0x0:(READ) flags 0x800 phys_seg 1 prio class 2
[ 232.890507] I/O error, dev loop0, sector 32776 op 0x0:(READ) flags 0x800 phys_seg 1 prio class 2
[ 232.896852] I/O error, dev loop0, sector 8 op 0x0:(READ) flags 0x800 phys_seg 1 prio class 2
[ 232.899924] I/O error, dev loop0, sector 32776 op 0x0:(READ) flags 0x800 phys_seg 1 prio class 2
[ 232.905884] I/O error, dev loop0, sector 8 op 0x0:(READ) flags 0x800 phys_seg 1 prio class 2
[ 232.957964] I/O error, dev loop0, sector 32776 op 0x0:(READ) flags 0x800 phys_seg 1 prio class 2
[ 232.964269] I/O error, dev loop0, sector 8 op 0x0:(READ) flags 0x800 phys_seg 1 prio class 2
[ 232.967302] I/O error, dev loop0, sector 32776 op 0x0:(READ) flags 0x800 phys_seg 1 prio class 2
[ 232.973229] I/O error, dev loop0, sector 8 op 0x0:(READ) flags 0x800 phys_seg 1 prio class 2
[ 237.642615] BTRFS info (device dm-2): first mount of filesystem 929bcce7-36fe-499e-8f75-ae48a4583b03
[ 237.642635] BTRFS info (device dm-2): using crc32c (crc32c-intel) checksum algorithm
[ 237.642646] BTRFS info (device dm-2): using free space tree
[ 237.650977] BTRFS info (device dm-2): enabling ssd optimizations
[ 237.650984] BTRFS info (device dm-2): auto enabling async discard
[ 244.673905] EXT4-fs (dm-0): unmounting filesystem e1e87c8d-bb94-4260-8c8c-9239b7208a6f.
[ 244.680078] blk_print_req_error: 434 callbacks suppressed
[ 244.680083] I/O error, dev loop0, sector 0 op 0x0:(READ) flags 0x800 phys_seg 1 prio class 2
[ 244.681218] I/O error, dev loop0, sector 0 op 0x0:(READ) flags 0x800 phys_seg 1 prio class 2
[ 244.682339] I/O error, dev loop0, sector 0 op 0x0:(READ) flags 0x800 phys_seg 1 prio class 2
[ 244.684180] I/O error, dev loop0, sector 16 op 0x0:(READ) flags 0x80700 phys_seg 1 prio class 2
[ 244.685178] I/O error, dev loop0, sector 32 op 0x0:(READ) flags 0x80700 phys_seg 2 prio class 2
[ 244.685219] I/O error, dev loop0, sector 16 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
[ 244.687116] Buffer I/O error on dev loop0, logical block 2, async page read
[ 244.688133] I/O error, dev loop0, sector 16 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
[ 244.689128] Buffer I/O error on dev loop0, logical block 2, async page read
[ 244.690228] I/O error, dev loop0, sector 48 op 0x0:(READ) flags 0x80700 phys_seg 1 prio class 2
[ 244.691220] I/O error, dev loop0, sector 32 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
[ 244.692191] Buffer I/O error on dev loop0, logical block 4, async page read
[ 244.693314] I/O error, dev loop0, sector 64 op 0x0:(READ) flags 0x80700 phys_seg 1 prio class 2
[ 244.694420] Buffer I/O error on dev loop0, logical block 8, async page read
[ 244.695501] Buffer I/O error on dev loop0, logical block 16, async page read
[ 244.696712] Buffer I/O error on dev loop0, logical block 32, async page read
[ 244.697819] Buffer I/O error on dev loop0, logical block 64, async page read
[ 244.698864] Buffer I/O error on dev loop0, logical block 128, async page read
[ 244.699886] Buffer I/O error on dev loop0, logical block 256, async page read
[ 244.700971] Buffer I/O error on dev loop0, logical block 512, async page read
[ 244.735249] EXT4-fs (sde2): unmounting filesystem 30f1dea2-b6a3-4566-b769-3304c63f13e9.