On Fri, 25 Feb 2011, Kyungmin Park wrote: > From: Kyungmin Park <kyungmin.park@xxxxxxxxxxx> > > FAT supports batched discard as ext4. > > Cited from Lukas words. > "The current solution is not ideal because of its bad performance impact. > So basic idea to improve things is to avoid discarding every time some > blocks are freed. and instead batching is together into bigger trims, > which tends to be more effective." > > You can find an information in detail at following URLs. > http://lwn.net/Articles/397538/ > http://lwn.net/Articles/383933/ > > Clearify the meaning of "len" (Cited form Lukas mail) > > Let the "O" be free (bytes, blocks, whatever), and "=" be used. > Now, we have a filesystem like this. > > OOOO==O===OO===OOOOO==O===O===OOOOOOO=== > ^ ^ > 0 40 > > This is how it supposed to wotk if you have called FITIRM with parameters: > > start = 0 > minlen = 2 > len = 20 > > So you will go through (blocks, bytes...) 0 -> 20 > > OOOO==O===OO===OOOOO==O===O===OOOOOOO=== > ^ ^ > 0 20 > > So, you will call discard on extents: > > 0-3 > You'll skip 6 because is smaller than minlen > 10-11 > 15-19 > > instead of > > 0-3 > 10-11 > 15-19 > 30-36 Hi thanks for the next version. And again I have to ask: Did you test it ? and how ? Did you tried xfstest No. 251 ? Couple of comments bellow. Thanks! -Lukas > > Signed-off-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx> > --- > Changelog v3: > Adjust the minlen from queue discard_granularity > Use the corrent len usage > Changelog v2: > Use the given start and len as Lukas comments > Check the queue supports discard feature > --- > diff --git a/fs/fat/fat.h b/fs/fat/fat.h > index f504089..08b53e1 100644 > --- a/fs/fat/fat.h > +++ b/fs/fat/fat.h > @@ -299,6 +299,7 @@ extern int fat_alloc_clusters(struct inode *inode, int *cluster, > int nr_cluster); > extern int fat_free_clusters(struct inode *inode, int cluster); > extern int fat_count_free_clusters(struct super_block *sb); > +extern int fat_trim_fs(struct super_block *sb, struct fstrim_range *range); > > /* fat/file.c */ > extern long fat_generic_ioctl(struct file *filp, unsigned int cmd, > diff --git a/fs/fat/fatent.c b/fs/fat/fatent.c > index b47d2c9..a8e3837 100644 > --- a/fs/fat/fatent.c > +++ b/fs/fat/fatent.c > @@ -1,6 +1,8 @@ > /* > * Copyright (C) 2004, OGAWA Hirofumi > * Released under GPL v2. > + * > + * Batched discard support by Kyungmin Park <kyungmin.park@xxxxxxxxxxx> > */ > > #include <linux/module.h> > @@ -541,6 +543,16 @@ out: > return err; > } > > +static int fat_issue_discard(struct super_block *sb, int cluster, int nr_clus) > +{ > + struct msdos_sb_info *sbi = MSDOS_SB(sb); > + sector_t block, nr_blocks; > + > + block = fat_clus_to_blknr(sbi, cluster); > + nr_blocks = nr_clus * sbi->sec_per_clus; > + return sb_issue_discard(sb, block, nr_blocks, GFP_NOFS, 0); > +} > + > int fat_free_clusters(struct inode *inode, int cluster) > { > struct super_block *sb = inode->i_sb; > @@ -575,11 +587,7 @@ int fat_free_clusters(struct inode *inode, int cluster) > if (cluster != fatent.entry + 1) { > int nr_clus = fatent.entry - first_cl + 1; > > - sb_issue_discard(sb, > - fat_clus_to_blknr(sbi, first_cl), > - nr_clus * sbi->sec_per_clus, > - GFP_NOFS, 0); > - > + fat_issue_discard(sb, first_cl, nr_clus); > first_cl = cluster; > } > } > @@ -683,3 +691,88 @@ out: > unlock_fat(sbi); > return err; > } > + > +int fat_trim_fs(struct super_block *sb, struct fstrim_range *range) > +{ > + struct msdos_sb_info *sbi = MSDOS_SB(sb); > + struct fatent_operations *ops = sbi->fatent_ops; > + struct fat_entry fatent; > + unsigned long reada_blocks, reada_mask, cur_block; > + int err = 0, free, count, entry; > + int start, len, minlen, trimmed; > + > + start = range->start >> sb->s_blocksize_bits; > + start = start / sbi->sec_per_clus; > + len = range->len >> sb->s_blocksize_bits; > + len = len / sbi->sec_per_clus; > + minlen = range->minlen >> sb->s_blocksize_bits; > + minlen = minlen / sbi->sec_per_clus; > + trimmed = 0; > + count = 0; > + > + lock_fat(sbi); > + if (sbi->free_clusters != -1 && sbi->free_clus_valid) > + goto out; > + > + reada_blocks = FAT_READA_SIZE >> sb->s_blocksize_bits; > + reada_mask = reada_blocks - 1; > + cur_block = 0; > + > + entry = 0; > + free = 0; > + fatent_init(&fatent); > + > + if (start < FAT_START_ENT) > + start = FAT_START_ENT; > + > + fatent_set_entry(&fatent, start); > + > + while (count < sbi->max_cluster) { > + if (fatent.entry >= sbi->max_cluster) > + fatent.entry = FAT_START_ENT; > + /* readahead of fat blocks */ > + if ((cur_block & reada_mask) == 0) { > + unsigned long rest = sbi->fat_length - cur_block; > + fat_ent_reada(sb, &fatent, min(reada_blocks, rest)); You really do not need new variable "rest" just for passing it into one function. Get rid of it. > + } > + cur_block++; > + > + err = fat_ent_read_block(sb, &fatent); > + if (err) > + goto out; > + > + do { > + if (ops->ent_get(&fatent) == FAT_ENT_FREE) { > + free++; > + if (!entry) > + entry = fatent.entry; > + if (count >= len && free >= minlen) { > + fat_issue_discard(sb, entry, free); > + trimmed += free; I really do not understand FAT code very much, but is this right ? Should not you be setting free = 0 ? What will happen if you'll end up in the same branch in next iteration ? -- free will be still set to previous value+1, bu you'll be discarding next entry. I am sorry but this whole thing is not very readable. > + } > + if (count >= len) > + goto done; > + } else if (entry) { > + if (free >= minlen) { > + fat_issue_discard(sb, entry, free); > + trimmed += free; > + } > + if (count >= len) > + goto done; > + free = 0; > + entry = 0; > + } I don't not see why you are testing count all the time since it has not been changed since the "if" condition started. how about doing one test before the "if" condition ? > + count++; > + } while (fat_ent_next(sbi, &fatent)); > + } > + if (free >= minlen) { > + fat_issue_discard(sb, entry, free); > + trimmed += free; > + } > +done: > + range->len = (trimmed * sbi->sec_per_clus) << sb->s_blocksize_bits; > + fatent_brelse(&fatent); > +out: > + unlock_fat(sbi); > + return err; > +} > diff --git a/fs/fat/file.c b/fs/fat/file.c > index 7257752..9910aba 100644 > --- a/fs/fat/file.c > +++ b/fs/fat/file.c > @@ -125,6 +125,36 @@ long fat_generic_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) > return fat_ioctl_get_attributes(inode, user_attr); > case FAT_IOCTL_SET_ATTRIBUTES: > return fat_ioctl_set_attributes(filp, user_attr); > + case FITRIM: > + { > + struct super_block *sb = inode->i_sb; > + struct request_queue *q = bdev_get_queue(sb->s_bdev); > + struct fstrim_range range; > + int ret = 0; > + > + if (!capable(CAP_SYS_ADMIN)) > + return -EPERM; > + > + if (!blk_queue_discard(q)) > + return -EOPNOTSUPP; > + > + if (copy_from_user(&range, (struct fstrim_range *)arg, > + sizeof(range))) > + return -EFAULT; > + > + range.minlen = max((unsigned int)range.minlen, > + q->limits.discard_granularity); > + ret = fat_trim_fs(sb, &range); > + if (ret < 0) > + return ret; > + > + if (copy_to_user((struct fstrim_range *)arg, &range, > + sizeof(range))) > + return -EFAULT; > + > + return 0; > + } > + > default: > return -ENOTTY; /* Inappropriate ioctl for device */ > } > -- -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
