ESP32 Forum

Posted: **Tue Apr 02, 2024 1:28 am**

I am using littlefs to store logs to internal flash and have been testing the behaviour when the littlefs partition is full. I expected a graceful failure of fopen() or fprintf() but I get a DivideByZero exception from lfs_alloc in the bowels of the library from fclose(). It seems that I need to leave 8K of unused space to avoid this. Am I missing some config?

ESP-IDF v5.1.2
litlefs v1.14.2

Posted: **Mon Apr 15, 2024 11:27 am**

Thank you for the report. We will investigate this. However it may be an issue on the LittleFS side. If so we will notify the maintainers.

Posted: **Mon Apr 15, 2024 6:53 pm**

@owenjames can you post the full log? I believe this is an upstream core littlefs issue (unexpected divide by zero); esp_littlefs should be reporting an appropriate error code. The log can help us raise an appropriate issue in https://github.com/littlefs-project/littlefs

Posted: **Tue Apr 16, 2024 1:45 am**

Sorry, I don't have the log now but my notes show the exception occurs in lfs.c (when block_count is zero):

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static int lfs_alloc(lfs_t *lfs, lfs_block_t *block) {
...
        // In order to keep our block allocator from spinning forever when our
        // filesystem is full, we mark points where there are no in-flight
        // allocations with a checkpoint before starting a set of allocations.
        //
        // If we've looked at all blocks since the last checkpoint, we report
        // the filesystem as out of storage.
        //
        if (lfs->lookahead.ckpoint <= 0) {
            LFS_ERROR("No more free space 0x%"PRIx32,
                    (lfs->lookahead.start + lfs->lookahead.next)
                        % lfs->cfg->block_count);
            return LFS_ERR_NOSPC;
        }

GeSHi © Codebox Plus Extension

Posted: **Tue Apr 16, 2024 11:14 pm**

In this context,

Code: Select all

block_count

is the number of blocks in the entire filesystem, not free ones remaining. In newer versions of littlefs, the

Code: Select all

lfs_config.block_count

value can be set to 0 to be inferred from an existing filesystem; on mount

Code: Select all

lfs.block_count

is then appropriately populated.

If you can get a fullstack trace, or other info, it would greatly help! Upstream littlefs does have exhaustion tests, and I cannot find a location by inspection where a DivideByZero could occur. Thanks!

Also, I just released esp_littlefs v1.14.3 that updates littlefs v2.9.0 to v2.9.1, incase that fixes anything.

Posted: **Wed Apr 17, 2024 3:41 am**

Based on huming2207 being able to reproduce it here: https://github.com/joltwallet/esp_littlefs/issues/183

I opened up a PR that may resolve the issue here: https://github.com/littlefs-project/littlefs/pull/966

Will update when it gets merged and and makes its way to esp_littlefs.

Posted: **Wed Apr 17, 2024 6:15 pm**

fixed in core littlefs v2.9.2, and subsequently in esp_littlefs v1.14.4

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