From: Theodore Ts'o Subject: [PATCH 3/3] libext2fs: Avoid creating unneeded new extents in ext2fs_extent_set_bmap() Date: Sun, 19 Jul 2009 23:57:05 -0400 Message-ID: <1248062225-710-3-git-send-email-tytso@mit.edu> References: <1248062225-710-1-git-send-email-tytso@mit.edu> Cc: Theodore Ts'o To: Ext4 Developers List Return-path: Received: from THUNK.ORG ([69.25.196.29]:59384 "EHLO thunker.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750847AbZGTD5P (ORCPT ); Sun, 19 Jul 2009 23:57:15 -0400 In-Reply-To: <1248062225-710-1-git-send-email-tytso@mit.edu> Sender: linux-ext4-owner@vger.kernel.org List-ID: Avoiding inserting a new extent if it is possible to merge the new block to the beginning or the end of the previous or next extent. Signed-off-by: "Theodore Ts'o" --- lib/ext2fs/extent.c | 118 ++++++++++++++++++++++++++++++++++++++++----------- 1 files changed, 93 insertions(+), 25 deletions(-) diff --git a/lib/ext2fs/extent.c b/lib/ext2fs/extent.c index c47fbcc..1505447 100644 --- a/lib/ext2fs/extent.c +++ b/lib/ext2fs/extent.c @@ -1146,11 +1146,14 @@ errcode_t ext2fs_extent_set_bmap(ext2_extent_handle_t handle, int mapped = 1; /* logical is mapped? */ int orig_height; int extent_uninit = 0; + int prev_uninit = 0; + int next_uninit = 0; int new_uninit = 0; int max_len = EXT_INIT_MAX_LEN; + int has_prev, has_next; blk64_t orig_lblk; struct extent_path *path; - struct ext2fs_extent extent; + struct ext2fs_extent extent, next_extent, prev_extent; struct ext2fs_extent newextent; struct ext2_extent_info info; @@ -1222,12 +1225,44 @@ errcode_t ext2fs_extent_set_bmap(ext2_extent_handle_t handle, /* * This may be the extent *before* the requested logical, * if it's currently unmapped. + * + * Get the previous and next leaf extents, if they are present. */ retval = ext2fs_extent_get(handle, EXT2_EXTENT_CURRENT, &extent); if (retval) goto done; if (extent.e_flags & EXT2_EXTENT_FLAGS_UNINIT) extent_uninit = 1; + retval = ext2fs_extent_get(handle, EXT2_EXTENT_NEXT_LEAF, &next_extent); + if (retval) { + has_next = 0; + if (retval != EXT2_ET_EXTENT_NO_NEXT) + goto done; + } else { + dbg_print_extent("set_bmap: next_extent", + &next_extent); + has_next = 1; + if (next_extent.e_flags & EXT2_EXTENT_FLAGS_UNINIT) + next_uninit = 1; + } + retval = ext2fs_extent_goto(handle, logical); + if (retval && retval != EXT2_ET_EXTENT_NOT_FOUND) + goto done; + retval = ext2fs_extent_get(handle, EXT2_EXTENT_PREV_LEAF, &prev_extent); + if (retval) { + has_prev = 0; + if (retval != EXT2_ET_EXTENT_NO_PREV) + goto done; + } else { + has_prev = 1; + dbg_print_extent("set_bmap: prev_extent", + &prev_extent); + if (prev_extent.e_flags & EXT2_EXTENT_FLAGS_UNINIT) + prev_uninit = 1; + } + retval = ext2fs_extent_goto(handle, logical); + if (retval && retval != EXT2_ET_EXTENT_NOT_FOUND) + goto done; /* check if already pointing to the requested physical */ if (mapped && (new_uninit == extent_uninit) && @@ -1248,6 +1283,28 @@ errcode_t ext2fs_extent_set_bmap(ext2_extent_handle_t handle, ((int) extent.e_len < max_len-1)) { extent.e_len++; retval = ext2fs_extent_replace(handle, 0, &extent); + } else if ((logical == extent.e_lblk - 1) && + (physical == extent.e_pblk - 1) && + (new_uninit == extent_uninit) && + ((int) extent.e_len < max_len - 1)) { + extent.e_len++; + extent.e_lblk--; + extent.e_pblk--; + retval = ext2fs_extent_replace(handle, 0, &extent); + } else if (has_next && + (logical == next_extent.e_lblk - 1) && + (physical == next_extent.e_pblk - 1) && + (new_uninit == next_uninit) && + ((int) next_extent.e_len < max_len - 1)) { + retval = ext2fs_extent_get(handle, + EXT2_EXTENT_NEXT_LEAF, + &next_extent); + if (retval) + goto done; + next_extent.e_len++; + next_extent.e_lblk--; + next_extent.e_pblk--; + retval = ext2fs_extent_replace(handle, 0, &next_extent); } else if (logical < extent.e_lblk) retval = ext2fs_extent_insert(handle, 0, &newextent); else @@ -1279,14 +1336,32 @@ errcode_t ext2fs_extent_set_bmap(ext2_extent_handle_t handle, #ifdef DEBUG printf("(re/un)mapping last block in extent\n"); #endif - /* Make sure insert works before replacing old extent */ if (physical) { - retval = ext2fs_extent_insert(handle, - EXT2_EXTENT_INSERT_AFTER, &newextent); + if (has_next && + (logical == (next_extent.e_lblk - 1)) && + (physical == (next_extent.e_pblk - 1)) && + (new_uninit == next_uninit) && + ((int) next_extent.e_len < max_len - 1)) { + retval = ext2fs_extent_get(handle, + EXT2_EXTENT_NEXT_LEAF, &next_extent); + if (retval) + goto done; + next_extent.e_len++; + next_extent.e_lblk--; + next_extent.e_pblk--; + retval = ext2fs_extent_replace(handle, 0, + &next_extent); + if (retval) + goto done; + } else + retval = ext2fs_extent_insert(handle, + EXT2_EXTENT_INSERT_AFTER, &newextent); if (retval) goto done; /* Now pointing at inserted extent; move back to prev */ - retval = ext2fs_extent_goto(handle, logical - 1); + retval = ext2fs_extent_get(handle, + EXT2_EXTENT_PREV_LEAF, + &extent); if (retval) goto done; } @@ -1299,30 +1374,23 @@ errcode_t ext2fs_extent_set_bmap(ext2_extent_handle_t handle, printf("(re/un)mapping first block in extent\n"); #endif if (physical) { - retval = ext2fs_extent_get(handle, - EXT2_EXTENT_PREV_LEAF, - &extent); - if (extent.e_flags & EXT2_EXTENT_FLAGS_UNINIT) - extent_uninit = 1; - if (retval == EXT2_ET_EXTENT_NO_PREV) { - retval = ext2fs_extent_goto(handle, logical); + if (has_prev && + (logical == (prev_extent.e_lblk + + prev_extent.e_len)) && + (physical == (prev_extent.e_pblk + + prev_extent.e_len)) && + (new_uninit == prev_uninit) && + ((int) prev_extent.e_len < max_len-1)) { + retval = ext2fs_extent_get(handle, + EXT2_EXTENT_PREV_LEAF, &prev_extent); if (retval) goto done; - retval = ext2fs_extent_insert(handle, - 0, &newextent); - } else if (retval) - goto done; - else if ((logical == extent.e_lblk + extent.e_len) && - (physical == extent.e_pblk + extent.e_len) && - (new_uninit == extent_uninit) && - ((int) extent.e_len < max_len-1)) { - extent.e_len++; + prev_extent.e_len++; retval = ext2fs_extent_replace(handle, 0, - &extent); - } else { + &prev_extent); + } else retval = ext2fs_extent_insert(handle, - EXT2_EXTENT_INSERT_AFTER, &newextent); - } + 0, &newextent); if (retval) goto done; retval = ext2fs_extent_get(handle, -- 1.6.3.2.1.gb9f7d.dirty