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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@mit.edu>
bitmap-optimize
Theodore Ts'o 2009-07-19 23:37:44 -04:00
parent 64cb68b3ea
commit 8b5ed492de
1 changed files with 93 additions and 25 deletions
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118
lib/ext2fs/extent.c
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@ -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;
prev_extent.e_len++;
retval = ext2fs_extent_replace(handle, 0,
&prev_extent);
} else
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++;
retval = ext2fs_extent_replace(handle, 0,
&extent);
} else {
retval = ext2fs_extent_insert(handle,
EXT2_EXTENT_INSERT_AFTER, &newextent);
}
if (retval)
goto done;
retval = ext2fs_extent_get(handle,