Non Aligned Reads

[Hemanth-Eduru]

Hi I am new to use of liburing I have the following doubts

1. What is the need of posix_memalign of the buffer which we will be passing to io_uring_prep_read I tried without alignment then it will throw error during read with cqe failed: Invalid argument
2. Is it possible to read data which not a multiple of 4k Bytes (or power of 2)?

[axboe]

This isn't related to io_uring, these are O_DIRECT restrictions. For O_DIRECT, you have to read in multiples of the sector size of the device. Depending on the kernel version, the buffer used must also be aligned to the sector size, or (in newer kernels), just aligned to the DMA restrictions of the device.

[Hemanth-Eduru]

Thanks for the quick reply, one more doubt, are these applicable even if do not use O_DIRECT flag while opening the file (just O_RDONLY flag)

[axboe]

No, as mentioned, these are O_DIRECT only restrictions.

[Hemanth-Eduru]

Thank you