1c0b8a7a62
HPFS needs to load 4 consecutive 512-byte sectors when accessing the directory nodes or bitmaps. We can't switch to 2048-byte block size because files are allocated in the units of 512-byte sectors. Previously, the driver would allocate a 2048-byte area using kmalloc, copy the data from four buffers to this area and eventually copy them back if they were modified. In the current implementation of the buffer cache, buffers are allocated in the pagecache. That means that 4 consecutive 512-byte buffers are stored in consecutive areas in the kernel address space. So, we don't need to allocate extra memory and copy the content of the buffers there. This patch optimizes the code to avoid copying the buffers. It checks if the four buffers are stored in contiguous memory - if they are not, it falls back to allocating a 2048-byte area and copying data there. Signed-off-by: Mikulas Patocka <mikulas@artax.karlin.mff.cuni.cz> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
205 lines
4.6 KiB
C
205 lines
4.6 KiB
C
/*
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* linux/fs/hpfs/buffer.c
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*
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* Mikulas Patocka (mikulas@artax.karlin.mff.cuni.cz), 1998-1999
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*
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* general buffer i/o
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*/
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#include <linux/sched.h>
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#include <linux/slab.h>
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#include <linux/blkdev.h>
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#include "hpfs_fn.h"
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void hpfs_prefetch_sectors(struct super_block *s, unsigned secno, int n)
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{
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struct buffer_head *bh;
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struct blk_plug plug;
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if (n <= 0 || unlikely(secno >= hpfs_sb(s)->sb_fs_size))
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return;
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bh = sb_find_get_block(s, secno);
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if (bh) {
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if (buffer_uptodate(bh)) {
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brelse(bh);
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return;
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}
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brelse(bh);
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};
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blk_start_plug(&plug);
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while (n > 0) {
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if (unlikely(secno >= hpfs_sb(s)->sb_fs_size))
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break;
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sb_breadahead(s, secno);
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secno++;
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n--;
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}
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blk_finish_plug(&plug);
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}
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/* Map a sector into a buffer and return pointers to it and to the buffer. */
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void *hpfs_map_sector(struct super_block *s, unsigned secno, struct buffer_head **bhp,
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int ahead)
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{
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struct buffer_head *bh;
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hpfs_lock_assert(s);
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hpfs_prefetch_sectors(s, secno, ahead);
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cond_resched();
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*bhp = bh = sb_bread(s, secno);
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if (bh != NULL)
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return bh->b_data;
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else {
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printk("HPFS: hpfs_map_sector: read error\n");
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return NULL;
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}
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}
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/* Like hpfs_map_sector but don't read anything */
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void *hpfs_get_sector(struct super_block *s, unsigned secno, struct buffer_head **bhp)
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{
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struct buffer_head *bh;
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/*return hpfs_map_sector(s, secno, bhp, 0);*/
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hpfs_lock_assert(s);
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cond_resched();
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if ((*bhp = bh = sb_getblk(s, secno)) != NULL) {
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if (!buffer_uptodate(bh)) wait_on_buffer(bh);
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set_buffer_uptodate(bh);
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return bh->b_data;
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} else {
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printk("HPFS: hpfs_get_sector: getblk failed\n");
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return NULL;
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}
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}
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/* Map 4 sectors into a 4buffer and return pointers to it and to the buffer. */
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void *hpfs_map_4sectors(struct super_block *s, unsigned secno, struct quad_buffer_head *qbh,
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int ahead)
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{
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char *data;
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hpfs_lock_assert(s);
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cond_resched();
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if (secno & 3) {
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printk("HPFS: hpfs_map_4sectors: unaligned read\n");
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return NULL;
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}
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hpfs_prefetch_sectors(s, secno, 4 + ahead);
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if (!(qbh->bh[0] = sb_bread(s, secno + 0))) goto bail0;
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if (!(qbh->bh[1] = sb_bread(s, secno + 1))) goto bail1;
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if (!(qbh->bh[2] = sb_bread(s, secno + 2))) goto bail2;
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if (!(qbh->bh[3] = sb_bread(s, secno + 3))) goto bail3;
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if (likely(qbh->bh[1]->b_data == qbh->bh[0]->b_data + 1 * 512) &&
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likely(qbh->bh[2]->b_data == qbh->bh[0]->b_data + 2 * 512) &&
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likely(qbh->bh[3]->b_data == qbh->bh[0]->b_data + 3 * 512)) {
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return qbh->data = qbh->bh[0]->b_data;
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}
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qbh->data = data = kmalloc(2048, GFP_NOFS);
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if (!data) {
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printk("HPFS: hpfs_map_4sectors: out of memory\n");
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goto bail4;
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}
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memcpy(data + 0 * 512, qbh->bh[0]->b_data, 512);
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memcpy(data + 1 * 512, qbh->bh[1]->b_data, 512);
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memcpy(data + 2 * 512, qbh->bh[2]->b_data, 512);
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memcpy(data + 3 * 512, qbh->bh[3]->b_data, 512);
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return data;
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bail4:
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brelse(qbh->bh[3]);
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bail3:
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brelse(qbh->bh[2]);
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bail2:
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brelse(qbh->bh[1]);
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bail1:
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brelse(qbh->bh[0]);
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bail0:
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return NULL;
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}
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/* Don't read sectors */
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void *hpfs_get_4sectors(struct super_block *s, unsigned secno,
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struct quad_buffer_head *qbh)
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{
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cond_resched();
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hpfs_lock_assert(s);
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if (secno & 3) {
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printk("HPFS: hpfs_get_4sectors: unaligned read\n");
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return NULL;
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}
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if (!hpfs_get_sector(s, secno + 0, &qbh->bh[0])) goto bail0;
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if (!hpfs_get_sector(s, secno + 1, &qbh->bh[1])) goto bail1;
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if (!hpfs_get_sector(s, secno + 2, &qbh->bh[2])) goto bail2;
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if (!hpfs_get_sector(s, secno + 3, &qbh->bh[3])) goto bail3;
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if (likely(qbh->bh[1]->b_data == qbh->bh[0]->b_data + 1 * 512) &&
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likely(qbh->bh[2]->b_data == qbh->bh[0]->b_data + 2 * 512) &&
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likely(qbh->bh[3]->b_data == qbh->bh[0]->b_data + 3 * 512)) {
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return qbh->data = qbh->bh[0]->b_data;
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}
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if (!(qbh->data = kmalloc(2048, GFP_NOFS))) {
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printk("HPFS: hpfs_get_4sectors: out of memory\n");
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goto bail4;
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}
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return qbh->data;
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bail4:
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brelse(qbh->bh[3]);
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bail3:
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brelse(qbh->bh[2]);
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bail2:
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brelse(qbh->bh[1]);
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bail1:
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brelse(qbh->bh[0]);
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bail0:
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return NULL;
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}
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void hpfs_brelse4(struct quad_buffer_head *qbh)
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{
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if (unlikely(qbh->data != qbh->bh[0]->b_data))
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kfree(qbh->data);
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brelse(qbh->bh[0]);
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brelse(qbh->bh[1]);
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brelse(qbh->bh[2]);
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brelse(qbh->bh[3]);
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}
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void hpfs_mark_4buffers_dirty(struct quad_buffer_head *qbh)
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{
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if (unlikely(qbh->data != qbh->bh[0]->b_data)) {
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memcpy(qbh->bh[0]->b_data, qbh->data + 0 * 512, 512);
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memcpy(qbh->bh[1]->b_data, qbh->data + 1 * 512, 512);
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memcpy(qbh->bh[2]->b_data, qbh->data + 2 * 512, 512);
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memcpy(qbh->bh[3]->b_data, qbh->data + 3 * 512, 512);
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}
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mark_buffer_dirty(qbh->bh[0]);
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mark_buffer_dirty(qbh->bh[1]);
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mark_buffer_dirty(qbh->bh[2]);
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mark_buffer_dirty(qbh->bh[3]);
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}
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