ext4

问题 This may sound noobish, especially as I'm ( as you may have guessed ) trying to write an Operating System. At the moment I'm stuck on trying to make a file system. What I want is a similar file system as Linux Ubuntu which is EXT4 ( at least mine is ). I want to try and also either write it in C. Any idea's on how I can go about this? And/or any tutorials that you might have found that may help me ( I have tried searching with no luck ) :L Thanks in advance! Jamie. 回答1: Really smart and

问题 Tim Bray's article "Saving Data Safely" left me with open questions. Today, it's over a month old and I haven't seen any follow-up on it, so I decided to address the topic here. One point of the article is that FileDescriptor.sync() should be called to be on the safe side when using FileOutputStream. At first, I was very irritated, because I never have seen any Java code doing a sync during the 12 years I do Java. Especially since coping with files is a pretty basic thing. Also, the standard

问题 journal mode data=journal mode provides full data and metadata journaling. All new data is written to the journal first, and then to its final location. In the event of a crash, the journal can be replayed, bringing both data and metadata into a consistent state. This mode is the slowest except when data needs to be read from and written to disk at the same time where it outperforms all others modes. Enabling this mode will disable delayed allocation and O_DIRECT support. Here I have a few

问题 Assume we have a file of FILE_SIZE bytes, and: FILE_SIZE <= min(page_size, physical_block_size) ; file size never changes (i.e. truncate() or append write() are never performed); file is modified only by completly overwriting its contents using: pwrite(fd, buf, FILE_SIZE, 0); Is it guaranteed on ext4 that: Such writes are atomic with respect to concurrent reads? Such writes are transactional with respect to a system crash? (i.e., after a crash the file's contents is completely from some

问题 Assume we have a file of FILE_SIZE bytes, and: FILE_SIZE <= min(page_size, physical_block_size) ; file size never changes (i.e. truncate() or append write() are never performed); file is modified only by completly overwriting its contents using: pwrite(fd, buf, FILE_SIZE, 0); Is it guaranteed on ext4 that: Such writes are atomic with respect to concurrent reads? Such writes are transactional with respect to a system crash? (i.e., after a crash the file's contents is completely from some

问题 Assume we have a file of FILE_SIZE bytes, and: FILE_SIZE <= min(page_size, physical_block_size) ; file size never changes (i.e. truncate() or append write() are never performed); file is modified only by completly overwriting its contents using: pwrite(fd, buf, FILE_SIZE, 0); Is it guaranteed on ext4 that: Such writes are atomic with respect to concurrent reads? Such writes are transactional with respect to a system crash? (i.e., after a crash the file's contents is completely from some

问题 I need to create a very high number of files which are not very large (like 4kb,8kb). It's not possible on my computer cause it takes all inodes up to 100% and I cannot create more files : $ df -i /dev/sda5 Filesystem Inodes IUsed IFree IUse% Mounted on /dev/sda5 54362112 36381206 17980906 67% /scratch (I started deleting files, it's why it's now 67%) The bytes-per-nodes are of 256 on my filesystem (ext4) $ sudo tune2fs -l /dev/sda5 | grep Inode Inode count: 54362112 Inodes per group: 8192

问题 I need to create a very high number of files which are not very large (like 4kb,8kb). It's not possible on my computer cause it takes all inodes up to 100% and I cannot create more files : $ df -i /dev/sda5 Filesystem Inodes IUsed IFree IUse% Mounted on /dev/sda5 54362112 36381206 17980906 67% /scratch (I started deleting files, it's why it's now 67%) The bytes-per-nodes are of 256 on my filesystem (ext4) $ sudo tune2fs -l /dev/sda5 | grep Inode Inode count: 54362112 Inodes per group: 8192

问题 I was wondering, for Bluetooth we have IEEE 802.15.1 standard, managed by Bluetooth Special Interest Group. For Wifi we have the IEEE 802.11 standards and also the Wifi Alliance. For NVMe SSDs on PCIe we have nvmexpress that regulate and publish its official documentation. So, usually there is a regulatory agency who decides things and standardize how some things should be to allow interoperability between several different implementations. But for the ext2/ext3/ext4 filesystems I didn't find

问题 This is a simple question but I've done some research and can't find any answers... So does anyone know if when we define extended attributes through xattr, those attributes are stored within - as a part of - the file'contents(in the biggining, in the end?), or if the inode has a special region to store these? And by the way, i've read that in ext4 "each extended attribute is limited to a filesystem block (e.g. 4 KiB)". I can't tell if this is enough if I wanted to store 7 extended attributes