Re: How to debug stuck read?

On Wed, Feb 02, 2022 at 07:15:14PM +0200, Dāvis Mosāns wrote:

I have a corrupted file on BTRFS which has CoW disabled thus no checksum. Trying to read this file causes the process to get stuck forever. It doesn't return EIO.

How can I find out why it gets stuck?

$ cat /proc/3449/stack | ./scripts/decode_stacktrace.sh vmlinux folio_wait_bit_common (mm/filemap.c:1314) filemap_get_pages (mm/filemap.c:2622) filemap_read (mm/filemap.c:2676) new_sync_read (fs/read_write.c:401 (discriminator 1))

folio_wait_bit_common() is where it waits for the page to be unlocked. Probably the problem is that btrfs isn't unlocking the page on seeing the error, so you don't get the -EIO returned?