Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753089AbaBCXN2 (ORCPT ); Mon, 3 Feb 2014 18:13:28 -0500 Received: from mail-qa0-f48.google.com ([209.85.216.48]:48840 "EHLO mail-qa0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751195AbaBCXN1 (ORCPT ); Mon, 3 Feb 2014 18:13:27 -0500 MIME-Version: 1.0 In-Reply-To: <87eh3kx1n6.fsf@devron.myhome.or.jp> References: <1387953112-2828-1-git-send-email-linkinjeon@gmail.com> <87eh3kx1n6.fsf@devron.myhome.or.jp> Date: Tue, 4 Feb 2014 08:13:26 +0900 Message-ID: Subject: Re: [PATCH v3 5/6] fat: permit to return phy block number by fibmap in fallocated region From: Namjae Jeon To: OGAWA Hirofumi Cc: akpm@linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Namjae Jeon , Amit Sahrawat Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2014-02-03, OGAWA Hirofumi : > Namjae Jeon writes: > >> From: Namjae Jeon >> >> Make the fibmap call the return the proper physical block number for any >> offset request in the fallocated range. >> >> Signed-off-by: Namjae Jeon >> Signed-off-by: Amit Sahrawat >> --- >> fs/fat/cache.c | 13 ++++++++++--- >> fs/fat/fat.h | 3 +++ >> fs/fat/inode.c | 3 +++ >> 3 files changed, 16 insertions(+), 3 deletions(-) >> >> diff --git a/fs/fat/cache.c b/fs/fat/cache.c >> index a132666..d22c1a2 100644 >> --- a/fs/fat/cache.c >> +++ b/fs/fat/cache.c >> @@ -325,19 +325,26 @@ int fat_bmap(struct inode *inode, sector_t sector, >> sector_t *phys, >> >> last_block = (i_size_read(inode) + (blocksize - 1)) >> blocksize_bits; >> if (sector >= last_block) { >> - if (!create) >> - return 0; >> - >> /* >> * Both ->mmu_private and ->i_disksize can access >> * on only allocation path. (caller must hold ->i_mutex) >> */ >> last_block = (MSDOS_I(inode)->i_disksize + (blocksize - 1)) >> >> blocksize_bits; >> + if (!create) { >> + /* Map a block in fallocated region */ >> + if (atomic_read(&MSDOS_I(inode)->beyond_isize)) >> + if (sector < last_block) >> + goto out_map_cluster; >> + >> + return 0; >> + } >> + >> if (sector >= last_block) >> return 0; >> } >> >> +out_map_cluster: >> cluster = sector >> (sbi->cluster_bits - sb->s_blocksize_bits); >> offset = sector & (sbi->sec_per_clus - 1); >> cluster = fat_bmap_cluster(inode, cluster); >> diff --git a/fs/fat/fat.h b/fs/fat/fat.h >> index 7b5851f..b884276 100644 >> --- a/fs/fat/fat.h >> +++ b/fs/fat/fat.h >> @@ -129,6 +129,9 @@ struct msdos_inode_info { >> struct hlist_node i_dir_hash; /* hash by i_logstart */ >> struct rw_semaphore truncate_lock; /* protect bmap against truncate */ >> struct inode vfs_inode; >> + >> + /* for getting block number beyond file size in case of fallocate */ >> + atomic_t beyond_isize; >> }; >> >> struct fat_slot_info { >> diff --git a/fs/fat/inode.c b/fs/fat/inode.c >> index 3636617..1c3192b 100644 >> --- a/fs/fat/inode.c >> +++ b/fs/fat/inode.c >> @@ -256,7 +256,10 @@ static sector_t _fat_bmap(struct address_space >> *mapping, sector_t block) >> >> /* fat_get_cluster() assumes the requested blocknr isn't truncated. */ >> down_read(&MSDOS_I(mapping->host)->truncate_lock); >> + /* To get block number beyond file size in fallocated region */ >> + atomic_set(&MSDOS_I(mapping->host)->beyond_isize, 1); >> blocknr = generic_block_bmap(mapping, block, fat_get_block); >> + atomic_set(&MSDOS_I(mapping->host)->beyond_isize, 0); >> up_read(&MSDOS_I(mapping->host)->truncate_lock); > > This is racy. While user is using bmap, kernel can allocate new blocks. > We should use another function for this. I understand that fat can map fallocated blocks in read case while user is using bmap. But I can not find the case allocate new blocks. If I am missing something, Could you please elaborate more ? Is it a case of _bmap request returning the block number for block allocated in parallel write path ? Thanks. > > For example, something like > > fat_get_block_bmap() > { > [...] > fat_get_block2(inode, iblock, &max_blocks, bh_result, create, bmap); > [...] > } > > blocknr = generic_block_bmap(mapping, block, fat_get_block_bmap); > -- > OGAWA Hirofumi > -- 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/