From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mingming Cao Subject: [PATCH 5/9] uninitialized extents handling Date: Wed, 09 Aug 2006 18:21:28 -0700 Message-ID: <1155172888.3161.84.camel@localhost.localdomain> Reply-To: cmm@us.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: linux-fsdevel@vger.kernel.org, ext2-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org Return-path: To: akpm@osdl.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: ext2-devel-bounces@lists.sourceforge.net Errors-To: ext2-devel-bounces@lists.sourceforge.net List-Id: linux-fsdevel.vger.kernel.org Make it possible to add file preallocation support in future as an RO_COMPAT feature by recognizing uninitialized extents as holes and limiting extent length to keep the top bit of ee_len free for marking uninitialized extents. Signed-off-by: Suparna Bhattacharya Signed-off-by: Mingming Cao --- linux-2.6.18-rc4-ming/fs/ext4/extents.c | 16 ++++++++++++++++ linux-2.6.18-rc4-ming/include/linux/ext4_fs_extents.h | 2 ++ 2 files changed, 18 insertions(+) diff -puN fs/ext4/extents.c~ext4-unitialized-extent-handling fs/ext4/extents.c --- linux-2.6.18-rc4/fs/ext4/extents.c~ext4-unitialized-extent-handling 2006-08-09 15:41:57.132331264 -0700 +++ linux-2.6.18-rc4-ming/fs/ext4/extents.c 2006-08-09 15:41:57.142331345 -0700 @@ -1082,6 +1082,13 @@ ext4_can_extents_be_merged(struct inode != le32_to_cpu(ex2->ee_block)) return 0; + /* + * To allow future support for preallocated extents to be added + * as an RO_COMPAT feature, refuse to merge to extents if + * can result in the top bit of ee_len being set + */ + if (le16_to_cpu(ex1->ee_len) + le16_to_cpu(ex2->ee_len) > EXT_MAX_LEN) + return 0; #ifdef AGRESSIVE_TEST if (le16_to_cpu(ex1->ee_len) >= 4) return 0; @@ -1943,6 +1950,15 @@ int ext4_ext_get_blocks(handle_t *handle unsigned long ee_block = le32_to_cpu(ex->ee_block); ext4_fsblk_t ee_start = ext_pblock(ex); unsigned short ee_len = le16_to_cpu(ex->ee_len); + + /* + * Allow future support for preallocated extents to be added + * as an RO_COMPAT feature: + * Uninitialized extents are treated as holes, except that + * we avoid (fail) allocating new blocks during a write. + */ + if (ee_len > EXT_MAX_LEN) + goto out2; /* if found exent covers block, simple return it */ if (iblock >= ee_block && iblock < ee_block + ee_len) { newblock = iblock - ee_block + ee_start; diff -puN include/linux/ext4_fs_extents.h~ext4-unitialized-extent-handling include/linux/ext4_fs_extents.h --- linux-2.6.18-rc4/include/linux/ext4_fs_extents.h~ext4-unitialized-extent-handling 2006-08-09 15:41:57.135331289 -0700 +++ linux-2.6.18-rc4-ming/include/linux/ext4_fs_extents.h 2006-08-09 15:41:57.143331354 -0700 @@ -141,6 +141,8 @@ typedef int (*ext_prepare_callback)(stru #define EXT_MAX_BLOCK 0xffffffff +#define EXT_MAX_LEN ((1UL << 15) - 1) + #define EXT_FIRST_EXTENT(__hdr__) \ ((struct ext4_extent *) (((char *) (__hdr__)) + \ _ ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642