Commit 6dfba108 authored Aug 15, 2025 by Chi Zhiling Committed by Namjae Jeon Sep 30, 2025

exfat: limit log print for IO error



For exFAT filesystems with 4MB read_ahead_size, removing the storage device
when the read operation is in progress, which cause the last read syscall
spent 150s [1]. The main reason is that exFAT generates excessive log
messages [2].

After applying this patch, approximately 300,000 lines of log messages
were suppressed, and the delay of the last read() syscall was reduced
to about 4 seconds.

[1]:
write(5, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072 <0.000120>
read(4, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072 <0.000032>
write(5, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 131072) = 131072 <0.000119>
read(4, 0x7fccf28ae000, 131072)         = -1 EIO (Input/output error) <150.186215>

[2]:
[  333.696603] exFAT-fs (vdb): error, failed to access to FAT (entry 0x0000d780, err:-5)
[  333.697378] exFAT-fs (vdb): error, failed to access to FAT (entry 0x0000d780, err:-5)
[  333.698156] exFAT-fs (vdb): error, failed to access to FAT (entry 0x0000d780, err:-5)

Signed-off-by: Chi Zhiling <chizhiling@kylinos.cn>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>

parent 30d4efb2

fs/exfat/fatent.c

+6 −5

Original line number	Diff line number	Diff line
		@@ -89,35 +89,36 @@ int exfat_ent_get(struct super_block *sb, unsigned int loc,
		int err;

		if (!is_valid_cluster(sbi, loc)) {
		exfat_fs_error(sb, "invalid access to FAT (entry 0x%08x)",
		exfat_fs_error_ratelimit(sb,
		"invalid access to FAT (entry 0x%08x)",
		loc);
		return -EIO;
		}

		err = __exfat_ent_get(sb, loc, content);
		if (err) {
		exfat_fs_error(sb,
		exfat_fs_error_ratelimit(sb,
		"failed to access to FAT (entry 0x%08x, err:%d)",
		loc, err);
		return err;
		}

		if (*content == EXFAT_FREE_CLUSTER) {
		exfat_fs_error(sb,
		exfat_fs_error_ratelimit(sb,
		"invalid access to FAT free cluster (entry 0x%08x)",
		loc);
		return -EIO;
		}

		if (*content == EXFAT_BAD_CLUSTER) {
		exfat_fs_error(sb,
		exfat_fs_error_ratelimit(sb,
		"invalid access to FAT bad cluster (entry 0x%08x)",
		loc);
		return -EIO;
		}

		if (content != EXFAT_EOF_CLUSTER && !is_valid_cluster(sbi, content)) {
		exfat_fs_error(sb,
		exfat_fs_error_ratelimit(sb,
		"invalid access to FAT (entry 0x%08x) bogus content (0x%08x)",
		loc, *content);
		return -EIO;