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libext2fs: batch calls to ext2fs_zero_blocks2()

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When allocating blocks for an indirect block mapped file, accumulate
blocks to be zero'ed and then call ext2fs_zero_blocks2() to zero them
in large chunks instead of block by block.

This significantly speeds up mkfs.ext3 since we don't send a large
number of ZERO_RANGE requests to the kernel, and while the kernel does
batch write requests, it is not batching ZERO_RANGE requests.  It's
more efficient to batch in userspace in any case, since it avoids
unnecessary system calls.

Reported-by: Mario Schuknecht <mario.schuknecht@dresearch-fe.de>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Theodore Ts'o 2020-04-25 11:41:24 -04:00
parent 2f6fd5da81
commit 86d6153417
1 changed files with 23 additions and 5 deletions
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28
lib/ext2fs/fallocate.c
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@ -805,7 +805,8 @@ errcode_t ext2fs_fallocate(ext2_filsys fs, int flags, ext2_ino_t ino,
blk64_t start, blk64_t len)
{
struct ext2_inode inode_buf;
blk64_t blk, x;
blk64_t blk, x, zero_blk, last = 0;
int zero_len = 0;
errcode_t err;
if (((flags & EXT2_FALLOCATE_FORCE_INIT) &&
@ -841,15 +842,32 @@ errcode_t ext2fs_fallocate(ext2_filsys fs, int flags, ext2_ino_t ino,
if (x)
continue;
err = ext2fs_bmap2(fs, ino, inode, NULL,
BMAP_ALLOC | BMAP_UNINIT | BMAP_ZERO, blk,
0, &x);
err = ext2fs_bmap2(fs, ino, inode, NULL, BMAP_ALLOC,
blk, 0, &x);
if (err)
return err;
goto errout;
if ((zero_len && (x != last+1)) ||
(zero_len >= 65536)) {
err = ext2fs_zero_blocks2(fs, zero_blk, zero_len,
NULL, NULL);
zero_len = 0;
if (err)
goto errout;
}
if (zero_len == 0) {
zero_blk = x;
zero_len = 1;
} else {
zero_len++;
}
last = x;
}
out:
if (inode == &inode_buf)
ext2fs_write_inode(fs, ino, inode);
errout:
if (zero_len)
ext2fs_zero_blocks2(fs, zero_blk, zero_len, NULL, NULL);
return err;
}