EXT4 In Linux 4.15 Gets Online Resizing When Using Bigalloc, Corruption Fixes
Written by Michael Larabel in Linux Storage on 13 November 2017 at 05:15 AM EST. 11 Comments
LINUX STORAGE --
Ted Ts'o was quick to send in the EXT4 file-system and fscrypt file-system encryption framework changes for the just-opened Linux 4.15 merge window.

On the fscrypt front, it's mostly just a random assortment of bug fixes.

With the EXT4 changes, they are a bit more exciting. First up is support for online resizing of EXT4 file-systems when using bigalloc. EXT4 has long supported online resizing but this is for where "EXT4_FEATURE_RO_COMPAT_BIGALLOC" has been enabled while the existing EXT4 resize interfaces remain in shape for 4.15. For those unfamiliar with the bigalloc mode, the EXT4 documentation explains, "The bigalloc feature changes ext4 to use clustered allocation, so that each bit in the ext4 block allocation bitmap addresses a power of two number of blocks. For example, if the file system is mainly going to be storing large files in the 4-32 megabyte range, it might make sense to set a cluster size of 1 megabyte. This means that each bit in the block allocation bitmap now addresses 256 4k blocks."

EXT4 also fixes some data corruption bugs, some involving DAX direct access mode and another corruption bug after a crash during a race condition with delayed allocation. There are also some EXT4 cleanups and optimizations. More details on those changes here.

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Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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