Andrew Morton wrote:
On Wed, 09 Aug 2006 18:21:00 -0700
Mingming Cao <[email protected]> wrote:
Redefine ext4 in-kernel filesystem block type (ext4_fsblk_t) from unsigned
long to sector_t, to allow kernel to handle >32 bit ext4 blocks.
I don't get it.
The intention is able to support 48bit ext4 on 64bit and 32bit arch
whenevern CONFIG_LBD is enabled (or when sector_t is actually 64 bit).
It just seems waste of memory to support 48bit in-kernel ext4 blks on 32
bit if CONFIG_LBD is disabled, since we won't support large device anyway.
ext3_fsblk_t was a unsigned long type before, which is always 32bit on
32bit arch. Thus we convert the ext3_fsblk_t to sector_t and depend on
CONFIG_LBD to decide whether we need 48bit in-kernel variables.(on-disk
block numbers are always 48 bit).
Randomly-chosen snippet:
@@ -274,7 +274,8 @@ static int find_group_orlov(struct super
freei = percpu_counter_read_positive(&sbi->s_freeinodes_counter);
avefreei = freei / ngroups;
freeb = percpu_counter_read_positive(&sbi->s_freeblocks_counter);
- avefreeb = freeb / ngroups;
+ avefreeb = freeb;
+ sector_div(avefreeb, ngroups);
ndirs = percpu_counter_read_positive(&sbi->s_dirs_counter);
if ((parent == sb->s_root->d_inode) ||
Here, `avefreeb' is still a 32-bit type. Why feed it into sector_div()?
avefreeb is ext3_fsblk_t type(sector_t type), which is 64bit on 64bit
arch and 64bit on 32bit arch if CONFIG_LBD is enabled.
@@ -303,13 +304,15 @@ static int find_group_orlov(struct super
goto fallback;
}
- blocks_per_dir = (le32_to_cpu(es->s_blocks_count) - freeb) / ndirs;
+ blocks_per_dir = le32_to_cpu(es->s_blocks_count) - freeb;
+ sector_div(blocks_per_dir, ndirs);
And here le32_to_cpu() is very much a 32-bit type. Why sector_div()?
ah, sorry about the confusing, s_blocks_count (the number of blocks on
this fs, on-disk) should be always 48bit value, and should not use
le32_to_cpu() to read-in. That is being fixed in [patch 9/9] 64bit
metadata support, where we convert 32 bit s_blocks_count to sector_t,
and also use mixro EXT4_BLOCKS_COUN(es) to read in the blocks count:
@@ -304,7 +306,7 @@ static int find_group_orlov(struct super
goto fallback;
}
- blocks_per_dir = le32_to_cpu(es->s_blocks_count) - freeb;
+ blocks_per_dir = EXT4_BLOCKS_COUNT(es) - freeb;
This patch[3/9] is just fix the in-kernel blocks type...We trying to do
this incrementally: first, support in-kernel blocks type >32bit, then
change the on-disk blocks type to >32bit.
And I agree with me: we want to get all the sector_t's out of this
filesystem. unsigned long long, do_div()?
Thanks,Mingming
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