[PATCH] exfat: limit log print for IO error

[PATCH] exfat: limit log print for IO error

[Chi Zhiling]

From: Chi Zhiling <chizhiling@kylinos.cn>

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>
---

There is another solution, feel free to comment:
https://lore.kernel.org/all/20250812072225.181798-1-chizhiling@163.com/

 fs/exfat/fatent.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/fs/exfat/fatent.c b/fs/exfat/fatent.c
index 232cc7f8ab92..825083634ba2 100644
--- a/fs/exfat/fatent.c
+++ b/fs/exfat/fatent.c
@@ -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;
-- 
2.43.0

Re: [PATCH] exfat: limit log print for IO error

[Namjae Jeon]

On Fri, Aug 15, 2025 at 6:33 PM Chi Zhiling <chizhiling@163.com> wrote:
>
> From: Chi Zhiling <chizhiling@kylinos.cn>
>
> 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>
Applied it to #dev.
Thanks!