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Fixed issue with cold-write after seek to block boundary

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This off-by-one error was caused by a slight difference between the
pos argument to lfs_index_find and lfs_index_extend. When pos is on
a block boundary, lfs_index_extend expects block to point before pos,
as it would when writing a file linearly. But when seeking to that
pos, the lfs_index_find to warm things up just supplies the block it
expects pos to be in.

Fixed the off-by-one error and added a test case for several of these
cold seek+writes.
This commit is contained in:
Christopher Haster
2017-09-17 12:53:18 -05:00
parent c2283a2753
commit 0982020fb3
2 changed files with 35 additions and 3 deletions
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lfs.c
+7 -3
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@@ -975,6 +975,7 @@ static int lfs_index_find(lfs_t *lfs,
return err;
}
assert(head >= 2 && head <= lfs->cfg->block_count);
current -= 1 << skip;
}
@@ -1054,6 +1055,8 @@ static int lfs_index_extend(lfs_t *lfs,
return err;
}
}
assert(head >= 2 && head <= lfs->cfg->block_count);
}
*off = 4*skips;
@@ -1428,18 +1431,17 @@ lfs_ssize_t lfs_file_write(lfs_t *lfs, lfs_file_t *file,
// check if we need a new block
if (!(file->flags & LFS_F_WRITING) ||
file->off == lfs->cfg->block_size) {
if (!(file->flags & LFS_F_WRITING)) {
if (!(file->flags & LFS_F_WRITING) && file->pos > 0) {
// find out which block we're extending from
int err = lfs_index_find(lfs, &file->cache, NULL,
file->head, file->size,
file->pos, &file->block, &file->off);
file->pos-1, &file->block, &file->off);
if (err) {
return err;
}
// mark cache as dirty since we may have read data into it
file->cache.block = 0xffffffff;
file->flags |= LFS_F_WRITING;
}
// extend file with new blocks
@@ -1450,6 +1452,8 @@ lfs_ssize_t lfs_file_write(lfs_t *lfs, lfs_file_t *file,
if (err) {
return err;
}
file->flags |= LFS_F_WRITING;
}
// program as much as we can in current block