read_block() and write_block() now accept the count (how many bytes to read
or write) and offset (where in the block to start; defaults to 0). Using these
new APIs, we can avoid doing copies between intermediary buffers in a lot more
cases. Hopefully this improves performance or something.
In contrast to the previous patchset that was reverted, this time we use
a "special" method to access a file with block size of 512 bytes (like
a harddrive essentially).
This was causing some obvious-in-hindsight but hard to spot bugs where
we'd implicitly convert the bool to an integer type and carry on with
the number 1 instead of the actual value().
Also, duplicate data in dbg() and klog() calls were removed.
In addition, leakage of virtual address to kernel log is prevented.
This is done by replacing kprintf() calls to dbg() calls with the
leaked data instead.
Also, other kprintf() calls were replaced with klog().
We don't have to log the process name/PID/TID, dbg() automatically adds
that as a prefix to every line.
Also we don't have to do .characters() on Strings passed to dbg() :^)
Linux creates holes in block lists for all-zero content. This is very
reasonable and we can now handle that situation as well.
Note that we're not smart enough to generate these holes ourselves yet,
but now we can at least read from such files.
Previously this API would return an InodeIdentifier, which meant that
there was a race in path resolution where an inode could be unlinked
in between finding the InodeIdentifier for a path component, and
actually resolving that to an Inode object.
Attaching a test that would quickly trip an assertion before.
Test: Kernel/path-resolution-race.cpp
This implementation uses the new helper method of Bitmap called
find_longest_range_of_unset_bits. This method looks for the biggest
range of contiguous bits unset in the bitmap and returns the start of
the range back to the caller.
We should use dbg() instead of dbgprintf() as much as possible to
protect ourselves against format string bugs. Here's a bunch of
conversions in Ext2FS.
As suggested by Joshua, this commit adds the 2-clause BSD license as a
comment block to the top of every source file.
For the first pass, I've just added myself for simplicity. I encourage
everyone to add themselves as copyright holders of any file they've
added or modified in some significant way. If I've added myself in
error somewhere, feel free to replace it with the appropriate copyright
holder instead.
Going forward, all new source files should include a license header.
Also don't uncache inodes when they reach i_links_count==0 unless they
also have no ref counts other than the +1 from the inode cache.
This prevents the FS from deleting the on-disk inode too soon.
If we're creating something that should have a different owner than the
current process's UID/GID, we need to plumb that all the way through
VFS down to the FS functions.
This adds a call to set_metadata_dirty(true) to
Ext2FS::write_directory(). This fixes a bug wherein InodeWatchers
weren't alerted on directory updates.
Files opened with O_DIRECT will now bypass the disk cache in read/write
operations (though metadata operations will still hit the disk cache.)
This will allow us to test actual disk performance instead of testing
disk *cache* performance, if that's what we want. :^)
There's room for improvment here, we're very aggressively flushing any
dirty cache entries for the specific block before reading/writing that
block. This is done by walking the entire cache, which may be slow.
Don't keep Inodes around in memory forever after we've interacted with
them once. This is a slight performance pessimization when accessing
the same file repeatedly, but closing it for a while in between.
Longer term we should find a way to keep a limited number of unused
Inodes cached, whichever ones we think are likely to be used again.
When creating a new directory, we set the initial size to 1 block.
This meant that we were allocating a block up front, but the Inode's
internal block list cache was not populated with this block.
This broke write_bytes() on a new directory, since it assumed that
the block list cache would be up to date if the call to write_bytes()
would not change the directory's size.
This patch fixes the issue in two ways: First, we cache the initial
block list created for new directories.
Second, we now repopulate the block list cache in write_bytes() if it
is empty when we get there. This is basically just a safety fallback
to avoid having this kind of bug in the future.
Also cache the block group descriptor table in a KBuffer on file system
initialization, instead of on first access.
This reduces pressure on the kmalloc heap somewhat.
We were writing out the full block list whenever Ext2FSInode::resize()
was called, even if the old and new sizes were identical.
This patch makes it a no-op, which drastically improves "cp" speed
since we now take full advantage of the up-front call to ftruncate().
If there are not enough free blocks in the filesystem to accomodate
growing an Inode, we should fail with ENOSPC before even starting to
allocate blocks.
