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Subject[PATCH 1/1] fat: improve sync performance by grouping writes in fat_mirror_bhs [really unmangled]
From: Holden Karau <holden@pigscanfly.ca> http://www.holdenkarau.com

This is an attempt at improving fat_mirror_bhs in sync mode [namely it
writes all of the data for a backup block, and then blocks untill
finished]. The old behaviour would write & block in smaller chunks, so
this should be slightly faster. It also removes the fixme requesting
that it be fixed to behave this way :-)
Signed-off-by: Holden Karau <holden@pigscanfly.ca> http://www.holdenkarau.com
---
Sorry about the mangled patch, this time it really shouldn't be mangled :-)
Important note; I do not normally play with filesystems. This MAY eat
your file system, it has not eaten mine but that does not mean much at
all [although I don't think it will]. I'd greatly appreciate comments
& suggestions. In case the patch gets mangled [again] I've put it up at
http://www.holdenkarau.com/~holden/projects/fat/001_improve_fat_sync_performance.patch


And now for the actual patch:

--- a/fs/fat/fatent.c 2006-09-19 23:42:06.000000000 -0400
+++ b/fs/fat/fatent.c 2006-10-25 19:14:14.000000000 -0400
@@ -1,5 +1,6 @@
/*
* Copyright (C) 2004, OGAWA Hirofumi
+ * Copyright (C) 2006, Holden Karau [Xandros]
* Released under GPL v2.
*/

@@ -343,34 +344,46 @@ int fat_ent_read(struct inode *inode, st
return ops->ent_get(fatent);
}

-/* FIXME: We can write the blocks as more big chunk. */
static int fat_mirror_bhs(struct super_block *sb, struct buffer_head **bhs,
- int nr_bhs)
+ int nr_bhs ) {
+ return fat_mirror_bhs_optw(sb , bhs , nr_bhs, 0);
+}
+
+static int fat_mirror_bhs_optw(struct super_block *sb, struct buffer_head **bhs,
+ int nr_bhs , int wait)
{
struct msdos_sb_info *sbi = MSDOS_SB(sb);
- struct buffer_head *c_bh;
+ struct buffer_head *c_bh[nr_bhs];
int err, n, copy;

+ /* Always wait if mounted -o sync */
+ if (sb->s_flags & MS_SYNCHRONOUS ) {
+ wait = 1;
+ }
+
err = 0;
+ err = fat_sync_bhs_optw( bhs , nr_bhs , wait);
+ if (err)
+ goto error;
for (copy = 1; copy < sbi->fats; copy++) {
sector_t backup_fat = sbi->fat_length * copy;
-
for (n = 0; n < nr_bhs; n++) {
- c_bh = sb_getblk(sb, backup_fat + bhs[n]->b_blocknr);
- if (!c_bh) {
+ c_bh[n] = sb_getblk(sb, backup_fat + bhs[n]->b_blocknr);
+ if (!c_bh[n]) {
err = -ENOMEM;
goto error;
}
- memcpy(c_bh->b_data, bhs[n]->b_data, sb->s_blocksize);
- set_buffer_uptodate(c_bh);
- mark_buffer_dirty(c_bh);
- if (sb->s_flags & MS_SYNCHRONOUS)
- err = sync_dirty_buffer(c_bh);
- brelse(c_bh);
+ set_buffer_uptodate(c_bh[n]);
+ mark_buffer_dirty(c_bh[n]);
+ memcpy(c_bh[n]->b_data, bhs[n]->b_data, sb->s_blocksize);
+ }
+ err = fat_sync_bhs_optw( c_bh , nr_bhs , wait );
+ for (n = 0; n < nr_bhs; n++ ) {
+ brelse(c_bh[n]);
+ }
if (err)
goto error;
}
- }
error:
return err;
}
@@ -383,12 +396,7 @@ int fat_ent_write(struct inode *inode, s
int err;

ops->ent_put(fatent, new);
- if (wait) {
- err = fat_sync_bhs(fatent->bhs, fatent->nr_bhs);
- if (err)
- return err;
- }
- return fat_mirror_bhs(sb, fatent->bhs, fatent->nr_bhs);
+ return fat_mirror_bhs_optw(sb, fatent->bhs, fatent->nr_bhs , wait);
}

static inline int fat_ent_next(struct msdos_sb_info *sbi,
@@ -505,9 +513,9 @@ out:
fatent_brelse(&fatent);
if (!err) {
if (inode_needs_sync(inode))
- err = fat_sync_bhs(bhs, nr_bhs);
- if (!err)
- err = fat_mirror_bhs(sb, bhs, nr_bhs);
+ err = fat_mirror_bhs_optw(sb , bhs, nr_bhs , 1);
+ else
+ err = fat_mirror_bhs_optw(sb, bhs, nr_bhs , 0 );
}
for (i = 0; i < nr_bhs; i++)
brelse(bhs[i]);
@@ -549,11 +557,6 @@ int fat_free_clusters(struct inode *inod
}

if (nr_bhs + fatent.nr_bhs > MAX_BUF_PER_PAGE) {
- if (sb->s_flags & MS_SYNCHRONOUS) {
- err = fat_sync_bhs(bhs, nr_bhs);
- if (err)
- goto error;
- }
err = fat_mirror_bhs(sb, bhs, nr_bhs);
if (err)
goto error;
@@ -564,11 +567,6 @@ int fat_free_clusters(struct inode *inod
fat_collect_bhs(bhs, &nr_bhs, &fatent);
} while (cluster != FAT_ENT_EOF);

- if (sb->s_flags & MS_SYNCHRONOUS) {
- err = fat_sync_bhs(bhs, nr_bhs);
- if (err)
- goto error;
- }
err = fat_mirror_bhs(sb, bhs, nr_bhs);
error:
fatent_brelse(&fatent);
--- a/fs/fat/misc.c 2006-09-19 23:42:06.000000000 -0400
+++ b/fs/fat/misc.c 2006-10-25 18:54:27.000000000 -0400
@@ -194,11 +194,17 @@ void fat_date_unix2dos(int unix_date, __

EXPORT_SYMBOL_GPL(fat_date_unix2dos);

-int fat_sync_bhs(struct buffer_head **bhs, int nr_bhs)
+
+int fat_sync_bhs(struct buffer_head **bhs, int nr_bhs ) {
+ return fat_sync_bhs_optw(bhs , nr_bhs , 1);
+}
+
+int fat_sync_bhs_optw(struct buffer_head **bhs, int nr_bhs ,int wait)
{
int i, err = 0;

ll_rw_block(SWRITE, nr_bhs, bhs);
+ if (wait) {
for (i = 0; i < nr_bhs; i++) {
wait_on_buffer(bhs[i]);
if (buffer_eopnotsupp(bhs[i])) {
@@ -207,6 +213,7 @@ int fat_sync_bhs(struct buffer_head **bh
} else if (!err && !buffer_uptodate(bhs[i]))
err = -EIO;
}
+ }
return err;
}

--- a/include/linux/msdos_fs.h 2006-09-19 23:42:06.000000000 -0400
+++ b/include/linux/msdos_fs.h 2006-10-25 18:53:50.000000000 -0400
@@ -419,6 +419,7 @@ extern int fat_chain_add(struct inode *i
extern int date_dos2unix(unsigned short time, unsigned short date);
extern void fat_date_unix2dos(int unix_date, __le16 *time, __le16 *date);
extern int fat_sync_bhs(struct buffer_head **bhs, int nr_bhs);
+extern int fat_sync_bhs_optw(struct buffer_head **bhs, int nr_bhs, int wait);

int fat_cache_init(void);
void fat_cache_destroy(void);
-
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