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2025-08-20docs: initramfs: file data alignment via name paddingDavid Disseldorp
The existing cpio extraction logic reads (maximum PATH_MAX) name_len bytes from the archive into the collected name buffer and ensures that the trailing byte is a null-terminator. This allows the actual file name to be shorter than name_len, with the name string simply zero-terminated prior to the last byte. Initramfs generators, such as dracut-cpio[1], can take advantage of name zero-padding to align file data segments within the archive to filesystem block boundaries. Block boundary alignment may allow the copy_file_range syscall to reflink archive source and destination extents. Link: https://github.com/dracutdevs/dracut/commit/300e4b116c624bca1b9e7251708b1ae656fe9157 [1] Signed-off-by: David Disseldorp <ddiss@suse.de> Reviewed-by: Nicolas Schier <nsc@kernel.org> Link: https://lore.kernel.org/r/20250819032607.28727-7-ddiss@suse.de Signed-off-by: Nathan Chancellor <nathan@kernel.org>
2025-04-07docs: initramfs: update compression and mtime descriptionsDavid Disseldorp
Update the document to reflect that initramfs didn't replace initrd following kernel 2.5.x. The initramfs buffer format now supports many compression types in addition to gzip, so include them in the grammar section. c_mtime use is dependent on CONFIG_INITRAMFS_PRESERVE_MTIME. Signed-off-by: David Disseldorp <ddiss@suse.de> Link: https://lore.kernel.org/r/20250402033949.852-2-ddiss@suse.de Reviewed-by: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Christian Brauner <brauner@kernel.org>
2019-07-15docs: early-userspace: move to driver-api guideMauro Carvalho Chehab
Those documents describe a kAPI. So, add to the driver-api book. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>