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Revision c4f675cd40d955d539180506c09515c90169b15b authored by Sergei Trofimovich on 20 May 2011, 20:20:30 UTC, committed by Chris Mason on 23 May 2011, 17:24:14 UTC 
btrfs: don't spin in shrink_delalloc if there is nothing to free
 
Observed as a large delay when --mixed filesystem is filled up.
Test example:
1. create tiny --mixed FS:
   $ dd if=/dev/zero of=2G.img seek=$((2048 * 1024 * 1024 - 1)) count=1 bs=1
   $ mkfs.btrfs --mixed 2G.img
   $ mount -oloop 2G.img /mnt/ut/
2. Try to fill it up:
   $ dd if=/dev/urandom of=10M.file bs=10240 count=1024
   $ seq 1 256 | while read file_no; do echo $file_no; time cp 10M.file ${file_no}.copy; done

Up to '200.copy' it goes fast, but when disk fills-up each -ENOSPC
message takes 3 seconds to pop-up _every_ ENOSPC (and in usermode linux
it's even more: 30-60 seconds!). (Maybe, time depends on kernel's timer resolution).

No IO, no CPU load, just rescheduling. Some debugging revealed busy spinning
in shrink_delalloc.

Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
Reviewed-by: Josef Bacik <josef@redhat.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
1 parent 0f3b708
Raw File
osf.c 
/*
 *  fs/partitions/osf.c
 *
 *  Code extracted from drivers/block/genhd.c
 *
 *  Copyright (C) 1991-1998  Linus Torvalds
 *  Re-organised Feb 1998 Russell King
 */

#include "check.h"
#include "osf.h"

#define MAX_OSF_PARTITIONS 18

int osf_partition(struct parsed_partitions *state)
{
	int i;
	int slot = 1;
	unsigned int npartitions;
	Sector sect;
	unsigned char *data;
	struct disklabel {
		__le32 d_magic;
		__le16 d_type,d_subtype;
		u8 d_typename[16];
		u8 d_packname[16];
		__le32 d_secsize;
		__le32 d_nsectors;
		__le32 d_ntracks;
		__le32 d_ncylinders;
		__le32 d_secpercyl;
		__le32 d_secprtunit;
		__le16 d_sparespertrack;
		__le16 d_sparespercyl;
		__le32 d_acylinders;
		__le16 d_rpm, d_interleave, d_trackskew, d_cylskew;
		__le32 d_headswitch, d_trkseek, d_flags;
		__le32 d_drivedata[5];
		__le32 d_spare[5];
		__le32 d_magic2;
		__le16 d_checksum;
		__le16 d_npartitions;
		__le32 d_bbsize, d_sbsize;
		struct d_partition {
			__le32 p_size;
			__le32 p_offset;
			__le32 p_fsize;
			u8  p_fstype;
			u8  p_frag;
			__le16 p_cpg;
		} d_partitions[MAX_OSF_PARTITIONS];
	} * label;
	struct d_partition * partition;

	data = read_part_sector(state, 0, &sect);
	if (!data)
		return -1;

	label = (struct disklabel *) (data+64);
	partition = label->d_partitions;
	if (le32_to_cpu(label->d_magic) != DISKLABELMAGIC) {
		put_dev_sector(sect);
		return 0;
	}
	if (le32_to_cpu(label->d_magic2) != DISKLABELMAGIC) {
		put_dev_sector(sect);
		return 0;
	}
	npartitions = le16_to_cpu(label->d_npartitions);
	if (npartitions > MAX_OSF_PARTITIONS) {
		put_dev_sector(sect);
		return 0;
	}
	for (i = 0 ; i < npartitions; i++, partition++) {
		if (slot == state->limit)
		        break;
		if (le32_to_cpu(partition->p_size))
			put_partition(state, slot,
				le32_to_cpu(partition->p_offset),
				le32_to_cpu(partition->p_size));
		slot++;
	}
	strlcat(state->pp_buf, "\n", PAGE_SIZE);
	put_dev_sector(sect);
	return 1;
}
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