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Date: Sun, 19 Jul 2009 23:57:05 -0400
From: Theodore Ts'o <tytso@....edu>
To: Ext4 Developers List <linux-ext4@...r.kernel.org>
Cc: Theodore Ts'o <tytso@....edu>
Subject: [PATCH 3/3] libext2fs: Avoid creating unneeded new extents in ext2fs_extent_set_bmap()
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" <tytso@....edu>
---
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
--
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