Hi Eric, Can this patch be merged now? On Fri, Feb 25, 2011 at 5:40 PM, Yongqiang Yang <xiaoqiangnk@xxxxxxxxx> wrote: > 1. lookup dirty pages with specified range in pagecache. > If no page is got, then there is no delayed-extent and > return with EXT_CONTINUE. > 2. find the 1st mapped buffer, > 3. check if the mapped buffer is both in the request range > and a delayed buffer. If not, there is no delayed-extent, > then return. > 4. a delayed-extent is found, the extent will be collected. > > Reported by Chris Mason <chris.mason@xxxxxxxxxx>: > We've had reports on btrfs that cp is giving us files full of zeros > instead of actually copying them. It was tracked down to a bug with > the btrfs fiemap implementation where it was returning holes for > delalloc ranges. > > Newer versions of cp are trusting fiemap to tell it where the holes > are, which does seem like a pretty neat trick. > > I decided to give xfs and ext4 a shot with a few tests cases too, xfs > passed with all the ones btrfs was getting wrong, and ext4 got the basic > delalloc case right. > $ mkfs.ext4 /dev/xxx > $ mount /dev/xxx /mnt > $ dd if=/dev/zero of=/mnt/foo bs=1M count=1 > $ fiemap-test foo > ext: 0 logical: [ 0.. 255] phys: 0.. 255 > flags: 0x007 tot: 256 > > Horray! But once we throw a hole in, things go bad: > $ mkfs.ext4 /dev/xxx > $ mount /dev/xxx /mnt > $ dd if=/dev/zero of=/mnt/foo bs=1M count=1 seek=1 > $ fiemap-test foo > < no output > > > We've got a delalloc extent after the hole and ext4 fiemap didn't find > it. If I run sync to kick the delalloc out: > $sync > $ fiemap-test foo > ext: 0 logical: [ 256.. 511] phys: 34048.. 34303 > flags: 0x001 tot: 256 > > fiemap-test is sitting in my /usr/local/bin, and I have no idea how it > got there. It's full of pretty comments so I know it isn't mine, but > you can grab it here: > > http://oss.oracle.com/~mason/fiemap-test.c > > xfsqa has a fiemap program too. > > After Fix, test results are as follows: > ext: 0 logical: [ 256.. 511] phys: 0.. 255 > flags: 0x007 tot: 256 > ext: 0 logical: [ 256.. 511] phys: 33280.. 33535 > flags: 0x001 tot: 256 > > $ mkfs.ext4 /dev/xxx > $ mount /dev/xxx /mnt > $ dd if=/dev/zero of=/mnt/foo bs=1M count=1 seek=1 > $ sync > $ dd if=/dev/zero of=/mnt/foo bs=1M count=1 seek=3 > $ dd if=/dev/zero of=/mnt/foo bs=1M count=1 seek=5 > $ fiemap-test foo > ext: 0 logical: [ 256.. 511] phys: 33280.. 33535 > flags: 0x000 tot: 256 > ext: 1 logical: [ 768.. 1023] phys: 0.. 255 > flags: 0x006 tot: 256 > ext: 2 logical: [ 1280.. 1535] phys: 0.. 255 > flags: 0x007 tot: 256 > > Signed-off-by: Yongqiang Yang <xiaoqiangnk@xxxxxxxxx> > --- > fs/ext4/extents.c | 149 +++++++++++++++++++++++++++++++++++++++-------------- > 1 files changed, 110 insertions(+), 39 deletions(-) > > diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c > index ccce8a7..9361adb 100644 > --- a/fs/ext4/extents.c > +++ b/fs/ext4/extents.c > @@ -3775,6 +3775,7 @@ int ext4_convert_unwritten_extents(struct inode *inode, loff_t offset, > } > return ret > 0 ? ret2 : ret; > } > + > /* > * Callback function called for each extent to gather FIEMAP information. > */ > @@ -3782,38 +3783,124 @@ static int ext4_ext_fiemap_cb(struct inode *inode, struct ext4_ext_path *path, > struct ext4_ext_cache *newex, struct ext4_extent *ex, > void *data) > { > - struct fiemap_extent_info *fieinfo = data; > - unsigned char blksize_bits = inode->i_sb->s_blocksize_bits; > __u64 logical; > __u64 physical; > __u64 length; > + loff_t size; > __u32 flags = 0; > - int error; > + int ret = 0; > + struct fiemap_extent_info *fieinfo = data; > + unsigned char blksize_bits; > > - logical = (__u64)newex->ec_block << blksize_bits; > + blksize_bits = inode->i_sb->s_blocksize_bits; > + logical = (__u64)newex->ec_block << blksize_bits; > > if (newex->ec_start == 0) { > - pgoff_t offset; > - struct page *page; > + /* > + * No extent in extent-tree contains block @newex->ec_start, > + * then the block may stay in 1)a hole or 2)delayed-extent. > + * > + * Holes or delayed-extents are processed as follows. > + * 1. lookup dirty pages with specified range in pagecache. > + * If no page is got, then there is no delayed-extent and > + * return with EXT_CONTINUE. > + * 2. find the 1st mapped buffer, > + * 3. check if the mapped buffer is both in the request range > + * and a delayed buffer. If not, there is no delayed-extent, > + * then return. > + * 4. a delayed-extent is found, the extent will be collected. > + */ > + ext4_lblk_t end = 0; > + pgoff_t last_offset; > + pgoff_t offset; > + struct page *page = NULL; > struct buffer_head *bh = NULL; > + struct buffer_head *head = NULL; > > offset = logical >> PAGE_SHIFT; > - page = find_get_page(inode->i_mapping, offset); > - if (!page || !page_has_buffers(page)) > - return EXT_CONTINUE; > - > - bh = page_buffers(page); > +repeat: > + last_offset = offset; > + head = NULL; > + ret = find_get_pages_tag(inode->i_mapping, &offset, > + PAGECACHE_TAG_DIRTY, 1, &page); > + > + if (!(flags & FIEMAP_EXTENT_DELALLOC)) { > + /* First time, try to find a mapped buffer. */ > + if (ret == 0) { > +out: > + if (ret > 0) > + page_cache_release(page); > + /* just a hole. */ > + return EXT_CONTINUE; > + } > > - if (!bh) > - return EXT_CONTINUE; > + /* Try to find the 1st mapped buffer. */ > + end = ((__u64)page->index << PAGE_SHIFT) > + >> blksize_bits; > + if (!page_has_buffers(page)) > + goto out; > + head = page_buffers(page); > + if (!head) > + goto out; > > - if (buffer_delay(bh)) { > - flags |= FIEMAP_EXTENT_DELALLOC; > - page_cache_release(page); > + bh = head; > + do { > + if (buffer_mapped(bh)) { > + /* get the 1st mapped buffer. */ > + if (end > newex->ec_block + > + newex->ec_len) > + /* The buffer is out of > + * the request range. > + */ > + goto out; > + goto found_mapped_buffer; > + } > + bh = bh->b_this_page; > + end++; > + } while (bh != head); > + /* No mapped buffer found. */ > + goto out; > } else { > + /*Find contiguous delayed buffers. */ > + if (ret > 0 && page->index == last_offset) > + head = page_buffers(page); > + bh = head; > + } > + > +found_mapped_buffer: > + if (bh != NULL && buffer_delay(bh)) { > + /* 1st or contiguous delayed buffer found. */ > + if (!(flags & FIEMAP_EXTENT_DELALLOC)) { > + /* > + * 1st delayed buffer found, record > + * the start of extent. > + */ > + flags |= FIEMAP_EXTENT_DELALLOC; > + newex->ec_block = end; > + logical = (__u64)end << blksize_bits; > + } > + /* Find contiguous delayed buffers. */ > + do { > + if (!buffer_delay(bh)) > + goto found_delayed_extent; > + bh = bh->b_this_page; > + end++; > + } while (bh != head); > + } else if (!(flags & FIEMAP_EXTENT_DELALLOC)) > + /* a hole found. */ > + goto out; > + > +found_delayed_extent: > + newex->ec_len = min(end - newex->ec_block, > + (ext4_lblk_t)EXT_INIT_MAX_LEN); > + if (ret == 1 && bh != NULL > + && newex->ec_len < EXT_INIT_MAX_LEN > + && buffer_delay(bh)) { > + /* Have not collected an extent and continue. */ > page_cache_release(page); > - return EXT_CONTINUE; > + goto repeat; > } > + page_cache_release(page); > } > > physical = (__u64)newex->ec_start << blksize_bits; > @@ -3822,32 +3909,16 @@ static int ext4_ext_fiemap_cb(struct inode *inode, struct ext4_ext_path *path, > if (ex && ext4_ext_is_uninitialized(ex)) > flags |= FIEMAP_EXTENT_UNWRITTEN; > > - /* > - * If this extent reaches EXT_MAX_BLOCK, it must be last. > - * > - * Or if ext4_ext_next_allocated_block is EXT_MAX_BLOCK, > - * this also indicates no more allocated blocks. > - * > - * XXX this might miss a single-block extent at EXT_MAX_BLOCK > - */ > - if (ext4_ext_next_allocated_block(path) == EXT_MAX_BLOCK || > - newex->ec_block + newex->ec_len - 1 == EXT_MAX_BLOCK) { > - loff_t size = i_size_read(inode); > - loff_t bs = EXT4_BLOCK_SIZE(inode->i_sb); > - > + size = i_size_read(inode); > + if (logical + length >= size) > flags |= FIEMAP_EXTENT_LAST; > - if ((flags & FIEMAP_EXTENT_DELALLOC) && > - logical+length > size) > - length = (size - logical + bs - 1) & ~(bs-1); > - } > > - error = fiemap_fill_next_extent(fieinfo, logical, physical, > + ret = fiemap_fill_next_extent(fieinfo, logical, physical, > length, flags); > - if (error < 0) > - return error; > - if (error == 1) > + if (ret < 0) > + return ret; > + if (ret == 1) > return EXT_BREAK; > - > return EXT_CONTINUE; > } > > -- > 1.7.4 > > -- Best Wishes Yongqiang Yang -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
