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Fixed inline files when inline_max == cache_size

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The initial implementation of inline files was thrown together fairly
quicky, however it has worked well so far and there hasn't been much
reason to change it.

One shortcut was to trick file writes into thinking they are writing to
imaginary blocks. This works well and reuses most of the file code
paths, as long as we don't flush the imaginary block out to disk.

Initially we did this by limiting inline_max to cache_max-1, ensuring
that the cache never fills up and gets flushed. This was a rather dirty
hack, the better solution, implemented here, is to handle the
representation of an "imaginary" block correctly all the way down into
the cache layer.

So now for files specifically, the value -1 represents a null pointer,
and the value -2 represents an "imaginary" block. This may become a
problem if the number of blocks approaches the max, however this -2
value is never written to disk and can be changed in the future without
breaking compatibility.
This commit is contained in:
Christopher Haster
2018-08-13 14:08:30 -05:00
parent d5e800575d
commit a2532a34cd
2 changed files with 11 additions and 6 deletions
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8
tests/test_alloc.sh
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@@ -341,6 +341,10 @@ tests/test.py << TEST
}
lfs_file_close(&lfs, &file[0]) => 0;
// remount to force reset of lookahead
lfs_unmount(&lfs) => 0;
lfs_mount(&lfs, &cfg) => 0;
// open hole
lfs_remove(&lfs, "bump") => 0;
@@ -350,7 +354,7 @@ tests/test.py << TEST
for (lfs_size_t i = 0; i < cfg.block_size; i += 2) {
memcpy(&buffer[i], "hi", 2);
}
lfs_file_write(&lfs, &file[0], buffer, cfg.block_size) => LFS_ERR_NOSPC;
lfs_file_write(&lfs, &file[0], buffer, 2*cfg.block_size) => LFS_ERR_NOSPC;
lfs_file_close(&lfs, &file[0]) => 0;
lfs_unmount(&lfs) => 0;
@@ -388,7 +392,6 @@ tests/test.py << TEST
// remount to force reset of lookahead
lfs_unmount(&lfs) => 0;
lfs_mount(&lfs, &cfg) => 0;
// rewrite one file
@@ -451,7 +454,6 @@ tests/test.py << TEST
// remount to force reset of lookahead
lfs_unmount(&lfs) => 0;
lfs_mount(&lfs, &cfg) => 0;
// rewrite one file with a hole of one block