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Add extfs optimized symlink write support.

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This commit is contained in:
Jonas 'Sortie' Termansen 2015-05-21 21:02:48 +02:00
parent 147aae31b1
commit ac785d861e
2 changed files with 68 additions and 15 deletions
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82
ext/inode.cpp
View file

@ -313,14 +313,34 @@ bool Inode::FreeIndirect(uint64_t from, uint64_t offset, uint32_t block_id,
void Inode::Truncate(uint64_t new_size)
{
if ( 0 < Size() && Size() <= 60 && !data->i_blocks )
{
fprintf(stderr, "extfs: Truncating optimized symlinks is not implemented!\n");
return;
}
// TODO: Enforce a filesize limit!
uint64_t old_size = Size();
bool could_be_embedded = old_size == 0 && EXT2_S_ISLNK(Mode()) && !data->i_blocks;
bool is_embedded = 0 < old_size && old_size <= 60 && !data->i_blocks;
if ( could_be_embedded || is_embedded )
{
if ( new_size <= 60 )
{
data_block->BeginWrite();
unsigned char* block_data = (unsigned char*) &data->i_block[0];
if ( old_size < new_size )
memset(block_data + old_size, 0, new_size - old_size);
if ( new_size < old_size )
memset(block_data + new_size, 0, old_size - new_size);
data->i_size = new_size;
data_block->FinishWrite();
return;
}
if ( is_embedded && !UnembedInInode() )
{
// Truncate() can't fail ATM so lose data instead of worse stuff.
data_block->BeginWrite();
unsigned char* block_data = (unsigned char*) &data->i_block[0];
memset(block_data, 0, 60);
data->i_size = 0;
data_block->FinishWrite();
}
}
// TODO: Enforce a filesize limit!
SetSize(new_size);
if ( old_size <= new_size )
return;
@ -701,8 +721,8 @@ ssize_t Inode::ReadAt(uint8_t* buf, size_t s_count, off_t o_offset)
// and so on.
if ( 0 < file_size && file_size <= 60 && !data->i_blocks )
{
assert(count <= 60);
unsigned char* block_data = (unsigned char*) &(data->i_block[0]);
assert(offset + count <= 60);
unsigned char* block_data = (unsigned char*) &data->i_block[0];
memcpy(buf, block_data + offset, count);
return (ssize_t) count;
}
@ -739,13 +759,18 @@ ssize_t Inode::WriteAt(const uint8_t* buf, size_t s_count, off_t o_offset)
uint64_t end_at = offset + count;
if ( offset < end_at )
/* TODO: Overflow! off_t overflow? */{};
if ( 0 < file_size && file_size <= 60 && !data->i_blocks )
{
fprintf(stderr, "extfs: Writing to optimized symlinks is not implemented!\n");
return errno = EROFS, -1;
}
if ( file_size < end_at )
Truncate(end_at);
if ( 0 < end_at && end_at <= 60 && !data->i_blocks )
{
data_block->BeginWrite();
unsigned char* block_data = (unsigned char*) &data->i_block[0];
memcpy(block_data + offset, buf, count);
if ( data->i_size < end_at )
data->i_size = end_at;
data_block->FinishWrite();
return (ssize_t) count;
}
while ( sofar < count )
{
uint64_t block_id = offset / filesystem->block_size;
@ -765,6 +790,30 @@ ssize_t Inode::WriteAt(const uint8_t* buf, size_t s_count, off_t o_offset)
return (ssize_t) sofar;
}
bool Inode::UnembedInInode()
{
assert(data->i_blocks == 0 && 0 < data->i_size && data->i_size <= 60);
unsigned char* block_data = (unsigned char*) &data->i_block[0];
size_t content_size = Size();
unsigned char content[60];
memcpy(content, block_data, content_size);
data_block->BeginWrite();
memset(block_data, 0, 60);
data->i_size = 0;
data_block->FinishWrite();
if ( WriteAt(content, content_size, 0) != (ssize_t) content_size )
{
Truncate(0);
data_block->BeginWrite();
memcpy(block_data, content, content_size);
data->i_size = content_size;
data->i_blocks = 0;
data_block->FinishWrite();
return false;
}
return true;
}
bool Inode::Rename(Inode* olddir, const char* oldname, const char* newname)
{
if ( !strcmp(oldname, ".") || !strcmp(oldname, "..") ||
@ -823,7 +872,10 @@ bool Inode::Symlink(const char* elem, const char* dest)
result->data->i_mtime = now.tv_sec;
// TODO: Set all the other inode properties!
if ( result->WriteAt((const uint8_t*) dest, strlen(dest), 0) < 0 )
size_t dest_length = strlen(dest);
if ( SSIZE_MAX < dest_length )
return errno = EFBIG, -1;
if ( result->WriteAt((const uint8_t*) dest, dest_length, 0) < (ssize_t) dest_length )
{
error:
memset(result->data, 0, sizeof(*result->data));

1
ext/inode.h
View file

@ -67,6 +67,7 @@ public:
Inode* Unlink(const char* elem, bool directories, bool force=false);
ssize_t ReadAt(uint8_t* buffer, size_t count, off_t offset);
ssize_t WriteAt(const uint8_t* buffer, size_t count, off_t offset);
bool UnembedInInode();
bool Rename(Inode* olddir, const char* oldname, const char* newname);
Inode* CreateDirectory(const char* path, mode_t mode);
bool RemoveDirectory(const char* path);