Re: [PATCH v6 25/31] ext4: submit and wait for disksize-grow I/O in fallocate paths

[sashiko-bot@kernel.org]

> From: Zhang Yi <yi.zhang@huawei.com>
> 
> Collapse range and insert range update i_disksize directly under
> i_data_sem. If the operation runs while the zeroed EOF block is still
> awaiting writeback, i_disksize could advance past the zeroed boundary
> before the zeroed data is persisted, exposing stale data on crash.
> 
> Deferring i_disksize updates like fallocate and zero_range is not an
> option here because the shift would move written extents beyond the
> current i_disksize. So flush and wait for the pending zeroed EOF block
> before these operations advance i_disksize. Since these operations
> already perform writeback, the extra flush does not add significant
> overhead.
> 
> In addition, for ext4_update_disksize_before_punch(), if the punch
> discards the pending block, the zeroed data will never be written back
> before advancing i_disksize, so it is also necessary to sync the
> pending EOF range there.
> 
> Finally, for the SYNC variants of zero_range and fallocate, this also
> guarantees the i_disksize update is persisted on the synchronous
> return.
> 
> Note that EXT4_STATE_DISKSIZE_GROW_PENDING is not set for now, and it
> will be set after everthing is done.
> 
> Signed-off-by: Zhang Yi <yi.zhang@huawei.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20260903123543.2302999-1-yi.zhang@huaweicloud.com?part=25