On Mon 24-12-12 15:55:36, Zheng Liu wrote:
> From: Zheng Liu <wenqing.lz@xxxxxxxxxx>
>
> es_pblk is used to record physical block that maps to the disk. es_status is
> used to record the status of the extent. Three status are defined, which are
> written, unwritten and delayed.
So this means one extent is 48 bytes on 64-bit architectures. If I'm a
nasty user and create artificially fragmented file (by allocating every
second block), extent tree takes 6 MB per GB of file. That's quite a bit
and I think you need to provide a way for kernel to reclaim extent
structures...
Honza
>
> Signed-off-by: Zheng Liu <wenqing.lz@xxxxxxxxxx>
> ---
> fs/ext4/extents_status.h | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/fs/ext4/extents_status.h b/fs/ext4/extents_status.h
> index 81e9339..85115bb 100644
> --- a/fs/ext4/extents_status.h
> +++ b/fs/ext4/extents_status.h
> @@ -20,10 +20,18 @@
> #define es_debug(fmt, ...) no_printk(fmt, ##__VA_ARGS__)
> #endif
>
> +enum {
> + EXTENT_STATUS_WRITTEN = 0, /* written extent */
> + EXTENT_STATUS_UNWRITTEN = 1, /* unwritten extent */
> + EXTENT_STATUS_DELAYED = 2, /* delayed extent */
> +};
> +
> struct extent_status {
> struct rb_node rb_node;
> ext4_lblk_t es_lblk; /* first logical block extent covers */
> ext4_lblk_t es_len; /* length of extent in block */
> + ext4_fsblk_t es_pblk; /* first physical block */
> + int es_status; /* record the status of extent */
> };
>
> struct ext4_es_tree {
> --
> 1.7.12.rc2.18.g61b472e
>
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--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
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