Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755308Ab3JIOkw (ORCPT ); Wed, 9 Oct 2013 10:40:52 -0400 Received: from mail-pd0-f176.google.com ([209.85.192.176]:36959 "EHLO mail-pd0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753871Ab3JIOkt (ORCPT ); Wed, 9 Oct 2013 10:40:49 -0400 From: Namjae Jeon To: hirofumi@mail.parknet.co.jp, akpm@linux-foundation.org Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, a.sahrawat@samsung.com, Namjae Jeon , Namjae Jeon Subject: [PATCH 2/5] fat: add fat_fallocate operation Date: Wed, 9 Oct 2013 23:40:40 +0900 Message-Id: <1381329640-11871-1-git-send-email-linkinjeon@gmail.com> X-Mailer: git-send-email 1.7.9.5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5817 Lines: 180 From: Namjae Jeon Implement preallocation via the fallocate syscall on VFAT partitions. This patch is based on an earlier patch of the same name which had some issues detailed below and did not get accepted. Refer https://lkml.org/lkml/2007/12/22/130. a) The preallocated space was not persistent when the FALLOC_FL_KEEP_SIZE flag was set. It will deallocate cluster at evict time. b) There was no need to zero out the clusters when the flag was set Instead of doing an expanding truncate, just allocate clusters and add them to the fat chain. This reduces preallocation time. Compatibility with windows: There are no issues when FALLOC_FL_KEEP_SIZE is not set because it just does an expanding truncate. Thus reading from the preallocated area on windows returns null until data is written to it. When a file with preallocated area using the FALLOC_FL_KEEP_SIZE was written to on windows, the windows driver freed-up the preallocated clusters and allocated new clusters for the new data. The freed up clusters gets reflected in the free space available for the partition which can be seen from the Volume properties. The windows chkdsk tool also does not report any errors on a disk containing files with preallocated space. And there is also no issue using linux fat fsck. because discard preallocated clusters at repair time. Signed-off-by: Namjae Jeon Signed-off-by: Amit Sahrawat --- fs/fat/file.c | 89 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ fs/fat/inode.c | 7 +++++ 2 files changed, 96 insertions(+) diff --git a/fs/fat/file.c b/fs/fat/file.c index 7301adb..03f716f 100644 --- a/fs/fat/file.c +++ b/fs/fat/file.c @@ -17,8 +17,12 @@ #include #include #include +#include #include "fat.h" +static long fat_fallocate(struct file *file, int mode, + loff_t offset, loff_t len); + static int fat_ioctl_get_attributes(struct inode *inode, u32 __user *user_attr) { u32 attr; @@ -182,6 +186,7 @@ const struct file_operations fat_file_operations = { #endif .fsync = fat_file_fsync, .splice_read = generic_file_splice_read, + .fallocate = fat_fallocate, }; static int fat_cont_expand(struct inode *inode, loff_t size) @@ -220,6 +225,90 @@ out: return err; } +/* + * Preallocate space for a file. This implements fat's fallocate file + * operation, which gets called from sys_fallocate system call. User + * space requests len bytes at offset. If FALLOC_FL_KEEP_SIZE is set + * we just allocate clusters without zeroing them out. Otherwise we + * allocate and zero out clusters via an expanding truncate. + */ +static long fat_fallocate(struct file *file, int mode, + loff_t offset, loff_t len) +{ + int cluster, fclus, dclus; + int nr_cluster; /* Number of clusters to be allocated */ + loff_t nr_bytes; /* Number of bytes to be allocated*/ + loff_t free_bytes; /* Unused bytes in the last cluster of file*/ + struct inode *inode = file->f_mapping->host; + struct super_block *sb = inode->i_sb; + struct msdos_sb_info *sbi = MSDOS_SB(sb); + int err = 0; + + /* No support for hole punch or other fallocate flags. */ + if (mode & ~FALLOC_FL_KEEP_SIZE) + return -EOPNOTSUPP; + + /* No support for dir */ + if (!S_ISREG(inode->i_mode)) + return -EOPNOTSUPP; + + mutex_lock(&inode->i_mutex); + if ((offset + len) <= MSDOS_I(inode)->i_disksize) + goto error; + + err = inode_newsize_ok(inode, (len + offset)); + if (err) { + mutex_unlock(&inode->i_mutex); + goto error; + } + + if (mode & FALLOC_FL_KEEP_SIZE) { + /* First compute the number of clusters to be allocated */ + if (inode->i_size > 0) { + err = fat_get_cluster(inode, FAT_ENT_EOF, + &fclus, &dclus); + if (err < 0) { + fat_msg(sb, KERN_ERR, + "fat_fallocate(): fat_get_cluster() error"); + goto error; + } + free_bytes = ((fclus + 1) << sbi->cluster_bits) - + inode->i_size; + nr_bytes = offset + len - inode->i_size - free_bytes; + } else + nr_bytes = offset + len - inode->i_size; + + nr_cluster = (nr_bytes + (sbi->cluster_size - 1)) >> + sbi->cluster_bits; + + /* Start the allocation.We are not zeroing out the clusters */ + while (nr_cluster-- > 0) { + err = fat_alloc_clusters(inode, &cluster, 1); + if (err) { + fat_msg(sb, KERN_ERR, + "fat_fallocate(): fat_alloc_clusters() error"); + goto error; + } + err = fat_chain_add(inode, cluster, 1); + if (err) { + fat_free_clusters(inode, cluster); + goto error; + } + MSDOS_I(inode)->i_disksize += sbi->cluster_size; + } + } else { + /* This is just an expanding truncate */ + err = fat_cont_expand(inode, (offset + len)); + if (err) + fat_msg(sb, KERN_ERR, + "fat_fallocate(): fat_cont_expand() error"); + } + +error: + mutex_unlock(&inode->i_mutex); + return err; +} + /* Free all clusters after the skip'th cluster. */ static int fat_free(struct inode *inode, int skip) { diff --git a/fs/fat/inode.c b/fs/fat/inode.c index 578a5db..2211489 100644 --- a/fs/fat/inode.c +++ b/fs/fat/inode.c @@ -491,6 +491,13 @@ EXPORT_SYMBOL_GPL(fat_build_inode); static void fat_evict_inode(struct inode *inode) { + struct super_block *sb = inode->i_sb; + + /* Release unwritten fallocated blocks on file release. */ + if (round_up(inode->i_size, sb->s_blocksize) < + MSDOS_I(inode)->i_disksize && inode->i_nlink != 0) + fat_truncate_blocks(inode, inode->i_size); + truncate_inode_pages(&inode->i_data, 0); if (!inode->i_nlink) { inode->i_size = 0; -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/