From: "Aneesh Kumar K.V" Subject: [PATCH -V2 for 2.6.31] ext4: Mark the unwritten buffer_head mapped during write_begin Date: Tue, 12 May 2009 20:49:56 +0530 Message-ID: <20090512151956.GD23862@skywalker> References: <1241693429-27588-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-ext4@vger.kernel.org To: cmm@us.ibm.com, tytso@mit.edu, sandeen@redhat.com Return-path: Received: from e28smtp07.in.ibm.com ([59.145.155.7]:45543 "EHLO e28smtp07.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752224AbZELPUQ (ORCPT ); Tue, 12 May 2009 11:20:16 -0400 Received: from d28relay04.in.ibm.com (d28relay04.in.ibm.com [9.184.220.61]) by e28smtp07.in.ibm.com (8.13.1/8.13.1) with ESMTP id n4CFKAsg015337 for ; Tue, 12 May 2009 20:50:10 +0530 Received: from d28av03.in.ibm.com (d28av03.in.ibm.com [9.184.220.65]) by d28relay04.in.ibm.com (8.13.8/8.13.8/NCO v9.2) with ESMTP id n4CFKAjQ1613916 for ; Tue, 12 May 2009 20:50:10 +0530 Received: from d28av03.in.ibm.com (loopback [127.0.0.1]) by d28av03.in.ibm.com (8.13.1/8.13.3) with ESMTP id n4CFKANi004658 for ; Wed, 13 May 2009 01:20:10 +1000 Content-Disposition: inline In-Reply-To: <1241693429-27588-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: Updated to apply cleanly after applying the version 5 of fake block number patches -aneesh ext4: Mark the unwritten buffer_head as mapped during write_begin From: Aneesh Kumar K.V This avoids multiple get_block calls during write. Now that we have unwritten buffer marked as mapped, we need to make sure writepages will handle unwritten buffer_heads also. With this patch we have the below: ext4_ext_get()_block returns unmapped, unwritten, buffer head when called with create = 0 for prealloc space. This makes sure we handle the read path and non-delayed allocation case correctly. Even though the buffer head is marked unmapped we have valid b_blocknr and b_bdev values in the buffer_head. ext4_da_get_block_prep called for block resrevation will now return mapped, unwritten, new buffer_head for prealloc space. This make sure we don't do multiple get_block calls for write to same offset. Also marking it new make sure sub-block zeroing of buffered writes happen correctly. Signed-off-by: Aneesh Kumar K.V Signed-off-by: "Theodore Ts'o" --- fs/ext4/extents.c | 4 +-- fs/ext4/inode.c | 79 ++++++++++++++++++++++++++++++++++------------------- 2 files changed, 52 insertions(+), 31 deletions(-) diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index 58be344..b1fdecc 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -2865,6 +2865,8 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode, if (create == EXT4_CREATE_UNINITIALIZED_EXT) goto out; if (!create) { + if (allocated > max_blocks) + allocated = max_blocks; /* * We have blocks reserved already. We * return allocated blocks so that delalloc @@ -2872,8 +2874,6 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode, * the buffer head will be unmapped so that * a read from the block returns 0s. */ - if (allocated > max_blocks) - allocated = max_blocks; set_buffer_unwritten(bh_result); bh_result->b_bdev = inode->i_sb->s_bdev; bh_result->b_blocknr = newblock; diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 9bf61e1..fcdda43 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -1846,7 +1846,7 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd) * @logical - first logical block to start assignment with * * the function goes through all passed space and put actual disk - * block numbers into buffer heads, dropping BH_Delay + * block numbers into buffer heads, dropping BH_Delay and BH_Unwritten */ static void mpage_put_bnr_to_bhs(struct mpage_da_data *mpd, sector_t logical, struct buffer_head *exbh) @@ -1896,16 +1896,24 @@ static void mpage_put_bnr_to_bhs(struct mpage_da_data *mpd, sector_t logical, do { if (cur_logical >= logical + blocks) break; - if (buffer_delay(bh)) { - bh->b_blocknr = pblock; - clear_buffer_delay(bh); - bh->b_bdev = inode->i_sb->s_bdev; - } else if (buffer_unwritten(bh)) { - bh->b_blocknr = pblock; - clear_buffer_unwritten(bh); - set_buffer_mapped(bh); - set_buffer_new(bh); - bh->b_bdev = inode->i_sb->s_bdev; + + if (buffer_delay(bh) || + buffer_unwritten(bh)) { + + BUG_ON(bh->b_bdev != inode->i_sb->s_bdev); + + if (buffer_delay(bh)) { + clear_buffer_delay(bh); + bh->b_blocknr = pblock; + } else { + /* + * unwritten already should have + * blocknr assigned. Verify that + */ + clear_buffer_unwritten(bh); + BUG_ON(bh->b_blocknr != pblock); + } + } else if (buffer_mapped(bh)) BUG_ON(bh->b_blocknr != pblock); @@ -2047,7 +2055,8 @@ static int mpage_da_map_blocks(struct mpage_da_data *mpd) * We consider only non-mapped and non-allocated blocks */ if ((mpd->b_state & (1 << BH_Mapped)) && - !(mpd->b_state & (1 << BH_Delay))) + !(mpd->b_state & (1 << BH_Delay)) && + !(mpd->b_state & (1 << BH_Unwritten))) return 0; new.b_state = 0; new.b_blocknr = 0; @@ -2186,6 +2195,17 @@ static void mpage_add_bh_to_extent(struct mpage_da_data *mpd, return; } +static int ext4_bh_unmapped_or_delay(handle_t *handle, struct buffer_head *bh) +{ + /* + * unmapped buffer is possible for holes. + * delay buffer is possible with delayed allocation. + * We also need to consider unwritten buffer as unmapped. + */ + return (!buffer_mapped(bh) || buffer_delay(bh) || + buffer_unwritten(bh)) && buffer_dirty(bh); +} + /* * __mpage_da_writepage - finds extent of pages and blocks * @@ -2270,8 +2290,7 @@ static int __mpage_da_writepage(struct page *page, * Otherwise we won't make progress * with the page in ext4_da_writepage */ - if (buffer_dirty(bh) && - (!buffer_mapped(bh) || buffer_delay(bh))) { + if (ext4_bh_unmapped_or_delay(NULL, bh)) { mpage_add_bh_to_extent(mpd, logical, bh->b_size, bh->b_state); @@ -2299,6 +2318,14 @@ static int __mpage_da_writepage(struct page *page, /* * this is a special callback for ->write_begin() only * it's intention is to return mapped block or reserve space + * + * For delayed buffer_head we have BH_Mapped, BH_New, BH_Delay set. + * We also have b_blocknr = -1 and b_bdev initialized properly + * + * For unwritten buffer_head we have BH_Mapped, BH_New, BH_Unwritten set. + * We also have b_blocknr = physicalblock mapping unwritten extent and b_bdev + * initialized properly. + * */ static int ext4_da_get_block_prep(struct inode *inode, sector_t iblock, struct buffer_head *bh_result, int create) @@ -2334,13 +2361,16 @@ static int ext4_da_get_block_prep(struct inode *inode, sector_t iblock, set_buffer_delay(bh_result); } else if (ret > 0) { bh_result->b_size = (ret << inode->i_blkbits); - /* - * With sub-block writes into unwritten extents - * we also need to mark the buffer as new so that - * the unwritten parts of the buffer gets correctly zeroed. - */ if (buffer_unwritten(bh_result)) { + /* a delayed write to unwritten bh should + * be marked new and mapped. Mapped ensures + * that we don't do get_block multiple times + * when we write to the same offset and new + * ensures that we do proper zero out for + * partial write + */ set_buffer_new(bh_result); + set_buffer_mapped(bh_result); } ret = 0; } @@ -2348,15 +2378,6 @@ static int ext4_da_get_block_prep(struct inode *inode, sector_t iblock, return ret; } -static int ext4_bh_unmapped_or_delay(handle_t *handle, struct buffer_head *bh) -{ - /* - * unmapped buffer is possible for holes. - * delay buffer is possible with delayed allocation - */ - return ((!buffer_mapped(bh) || buffer_delay(bh)) && buffer_dirty(bh)); -}