[RFC][Update][Patch 6/16]handing unitialized extents
Mingming Cao <[email protected]>
| Newsgroups | gmane.comp.file-systems.ext2.devel,gmane.linux.kernel,gmane.linux.file-systems |
|---|---|
| Organization | IBM LTC |
| Message-ID | <[email protected]> |
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 <[email protected]> Signed-off-by: Mingming Cao <[email protected]> --- linux-2.6.17-ming/fs/ext3/extents.c | 16 ++++++++++++++++ linux-2.6.17-ming/include/linux/ext3_fs_extents.h | 2 ++ 2 files changed, 18 insertions(+) diff -puN fs/ext3/extents.c~ext3-unitialized-extent-handling fs/ext3/extents.c --- linux-2.6.17/fs/ext3/extents.c~ext3-unitialized-extent-handling 2006-06-28 16:46:49.657758078 -0700 +++ linux-2.6.17-ming/fs/ext3/extents.c 2006-06-28 16:46:49.667756930 -0700 @@ -1082,6 +1082,13 @@ ext3_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 ext3_ext_get_blocks(handle_t *handle unsigned long ee_block = le32_to_cpu(ex->ee_block); ext3_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/ext3_fs_extents.h~ext3-unitialized-extent-handling include/linux/ext3_fs_extents.h --- linux-2.6.17/include/linux/ext3_fs_extents.h~ext3-unitialized-extent-handling 2006-06-28 16:46:49.661757619 -0700 +++ linux-2.6.17-ming/include/linux/ext3_fs_extents.h 2006-06-28 16:46:49.668756816 -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 ext3_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