diff options
| -rw-r--r-- | fs/ext4/inode.c | 86 |
1 files changed, 55 insertions, 31 deletions
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 8b7564d..fd5f27a 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -892,6 +892,10 @@ err_out: } /* + * The ext4_ind_get_blocks() function handles non-extents inodes + * (i.e., using the traditional indirect/double-indirect i_blocks + * scheme) for ext4_get_blocks(). + * * Allocation strategy is simple: if we have to allocate something, we will * have to go the whole way to leaf. So let's do it before attaching anything * to tree, set linkage between the newborn blocks, write them if sync is @@ -909,10 +913,11 @@ err_out: * return = 0, if plain lookup failed. * return < 0, error case. * - * - * Need to be called with - * down_read(&EXT4_I(inode)->i_data_sem) if not allocating file system block - * (ie, create is zero). Otherwise down_write(&EXT4_I(inode)->i_data_sem) + * The ext4_ind_get_blocks() function should be called with + * down_write(&EXT4_I(inode)->i_data_sem) if allocating filesystem + * blocks (i.e., flags has EXT4_GET_BLOCKS_CREATE set) or + * down_read(&EXT4_I(inode)->i_data_sem) if not allocating file system + * blocks. */ static int ext4_ind_get_blocks(handle_t *handle, struct inode *inode, ext4_lblk_t iblock, unsigned int maxblocks, @@ -1152,8 +1157,8 @@ int ext4_get_blocks(handle_t *handle, struct inode *inode, sector_t block, clear_buffer_unwritten(bh); /* - * Try to see if we can get the block without requesting - * for new file system block. + * Try to see if we can get the block without requesting a new + * file system block. */ down_read((&EXT4_I(inode)->i_data_sem)); if (EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL) { @@ -2000,6 +2005,12 @@ static void ext4_print_free_blocks(struct inode *inode) return; } +/* + * This function is used by mpage_da_map_blocks(). We separate it out + * as a separate function just to make life easier, and because + * mpage_da_map_blocks() used to be a generic function that took a + * get_block_t. + */ static int ext4_da_get_block_write(struct inode *inode, sector_t iblock, struct buffer_head *bh_result) { @@ -2031,8 +2042,8 @@ static int ext4_da_get_block_write(struct inode *inode, sector_t iblock, /* * Update on-disk size along with block allocation we don't - * use 'extend_disksize' as size may change within already - * allocated block -bzzz + * use EXT4_GET_BLOCKS_EXTEND_DISKSIZE as size may change + * within already allocated block -bzzz */ disksize = ((loff_t) iblock + ret) << inode->i_blkbits; if (disksize > i_size_read(inode)) @@ -2338,8 +2349,9 @@ 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 + * This is a special get_blocks_t callback which is used by + * ext4_da_write_begin(). It will either return mapped block or + * reserve space for a single block. * * For delayed buffer_head we have BH_Mapped, BH_New, BH_Delay set. * We also have b_blocknr = -1 and b_bdev initialized properly @@ -2347,7 +2359,6 @@ static int __mpage_da_writepage(struct page *page, * 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) @@ -2400,7 +2411,23 @@ static int ext4_da_get_block_prep(struct inode *inode, sector_t iblock, return ret; } -static int ext4_normal_get_block_write(struct inode *inode, sector_t iblock, +/* + * This function is used as a standard get_block_t calback function + * when there is no desire to allocate any blocks. It is used as a + * callback function for block_prepare_write(), nobh_writepage(), and + * block_write_full_page(). These functions should only try to map a + * single block at a time. + * + * Since this function doesn't do block allocations even if the caller + * requests it by passing in create=1, it is critically important that + * any caller checks to make sure that any buffer heads are returned + * by this function are either all already mapped or marked for + * delayed allocation before calling nobh_writepage() or + * block_write_full_page(). Otherwise, b_blocknr could be left + * unitialized, and the page write functions will be taken by + * surprise. + */ +static int noalloc_get_block_write(struct inode *inode, sector_t iblock, struct buffer_head *bh_result, int create) { int ret = 0; @@ -2419,10 +2446,11 @@ static int ext4_normal_get_block_write(struct inode *inode, sector_t iblock, } /* - * get called vi ext4_da_writepages after taking page lock (have journal handle) - * get called via journal_submit_inode_data_buffers (no journal handle) - * get called via shrink_page_list via pdflush (no journal handle) - * or grab_page_cache when doing write_begin (have journal handle) + * This function can get called via... + * - ext4_da_writepages after taking page lock (have journal handle) + * - journal_submit_inode_data_buffers (no journal handle) + * - shrink_page_list via pdflush (no journal handle) + * - grab_page_cache when doing write_begin (have journal handle) */ static int ext4_da_writepage(struct page *page, struct writeback_control *wbc) @@ -2473,7 +2501,7 @@ static int ext4_da_writepage(struct page *page, * do block allocation here. */ ret = block_prepare_write(page, 0, PAGE_CACHE_SIZE, - ext4_normal_get_block_write); + noalloc_get_block_write); if (!ret) { page_bufs = page_buffers(page); /* check whether all are mapped and non delay */ @@ -2498,11 +2526,10 @@ static int ext4_da_writepage(struct page *page, } if (test_opt(inode->i_sb, NOBH) && ext4_should_writeback_data(inode)) - ret = nobh_writepage(page, ext4_normal_get_block_write, wbc); + ret = nobh_writepage(page, noalloc_get_block_write, wbc); else - ret = block_write_full_page(page, - ext4_normal_get_block_write, - wbc); + ret = block_write_full_page(page, noalloc_get_block_write, + wbc); return ret; } @@ -2814,7 +2841,7 @@ retry: *pagep = page; ret = block_write_begin(file, mapping, pos, len, flags, pagep, fsdata, - ext4_da_get_block_prep); + ext4_da_get_block_prep); if (ret < 0) { unlock_page(page); ext4_journal_stop(handle); @@ -3122,12 +3149,10 @@ static int __ext4_normal_writepage(struct page *page, struct inode *inode = page->mapping->host; if (test_opt(inode->i_sb, NOBH)) - return nobh_writepage(page, - ext4_normal_get_block_write, wbc); + return nobh_writepage(page, noalloc_get_block_write, wbc); else - return block_write_full_page(page, - ext4_normal_get_block_write, - wbc); + return block_write_full_page(page, noalloc_get_block_write, + wbc); } static int ext4_normal_writepage(struct page *page, @@ -3179,7 +3204,7 @@ static int __ext4_journalled_writepage(struct page *page, int err; ret = block_prepare_write(page, 0, PAGE_CACHE_SIZE, - ext4_normal_get_block_write); + noalloc_get_block_write); if (ret != 0) goto out_unlock; @@ -3264,9 +3289,8 @@ static int ext4_journalled_writepage(struct page *page, * really know unless we go poke around in the buffer_heads. * But block_write_full_page will do the right thing. */ - return block_write_full_page(page, - ext4_normal_get_block_write, - wbc); + return block_write_full_page(page, noalloc_get_block_write, + wbc); } no_write: redirty_page_for_writepage(wbc, page); |
