Re: Do I have to fsync after aio_write finishes (with fallocate preallocation) ?

[Dave Chinner <david@fromorbit.com>]

On Sat, Aug 26, 2023 at 06:09:13PM -0700, Shawn wrote:
> xfs_io shows "extsize" as 0.   The data bsize is always 4096.  What's
> the implication of a 0 extsize?
> 
> $ sudo xfs_io -c 'stat' /mnt/S48BNW0K700192T/
> fd.path = "/mnt/S48BNW0K700192T/"
> fd.flags = non-sync,non-direct,read-write
> stat.ino = 64
> stat.type = directory
> stat.size = 81
> stat.blocks = 0
> fsxattr.xflags = 0x0 [--------------]
> fsxattr.projid = 0
> fsxattr.extsize = 0    <====  0
> fsxattr.nextents = 0
> fsxattr.naextents = 0
> dioattr.mem = 0x200
> dioattr.miniosz = 512
> dioattr.maxiosz = 2147483136

THere are no xflags set, meaning the XFS_DIFLAG_EXTSZINHERIT is not
set on the directory so nothing will inherit the extsize from the
directory at creation time. An extsize of zero is the default "don't
do any non-default extent size alignment" (i.e. align to stripe
parameters if the filesystem has them set, but nothing else.)

If this is the root directory of a mounted filesystem, it means the
extent size hint was not set by mkfs, and it hasn't been set
manually via xfs_io after mount, either.

-Dave.
-- 
Dave Chinner
david@fromorbit.com