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On Wed, Jun 21, 2017 at 06:49:36PM -0700, Tahsin Erdogan wrote:
> New ea_inode feature allows putting large xattr values into external
> inodes. struct ext4_xattr_entry and the attribute name however have to
> remain in the inode extra space or external attribute block. Once that
> space is exhausted, no further entries can be added. Some of that space
> could also be used by values that fit in there at the time of addition.
>
> So, a single xattr entry whose value barely fits in the external block
> could prevent further entries being added.
>
> To mitigate the problem, this patch introduces a notion of reserve in
> the
> external attribute block that cannot be used by value data. This reserve
> is enforced when ea_inode feature is enabled. The amount of reserve is
> arbitrarily chosen to be min(block_size/8, 1024). The table below shows
> how much space is reserved for each block size and the guaranteed
> mininum
> number of entries that can be placed in the external attribute block.
>
> block size reserved bytes entries (name length = 16)
> 1k 128 3
> 2k 256 7
> 4k 512 15
> 8k 1024 31
> 16k 1024 31
> 32k 1024 31
> 64k 1024 31
>
> Signed-off-by: Tahsin Erdogan <tahsin@google.com>

Thanks, applied.

- Ted

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