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author | Linus Torvalds <torvalds@linux-foundation.org> | 2018-08-13 22:34:47 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2018-08-13 22:34:47 -0700 |
commit | 10f3e23f07cb0c20f9bcb77a5b5a7eb2a1b2a2fe (patch) | |
tree | 1fcb34309b3542512c6f3345f092f7adb8c3312c /Documentation/filesystems/ext4/ondisk/blocks.rst | |
parent | 3bb37da509e576c80180fa0e4d1cfcaddf0cb82e (diff) | |
parent | 863c37fcb14f8b66ea831b45fb35a53ac4a8d69e (diff) | |
download | linux-10f3e23f07cb0c20f9bcb77a5b5a7eb2a1b2a2fe.tar.bz2 |
Merge tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4
Pull ext4 updates from Ted Ts'o:
- Convert content from the ext4 wiki to Documentation rst files so it
is more likely to be updated as we add new features to ext4.
- Add 64-bit timestamp support to ext4's superblock fields.
- ... and the usual bug fixes and cleanups, including a Spectre gadget
fixup and some hardening against maliciously corrupted file systems.
* tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4: (34 commits)
ext4: remove unneeded variable "err" in ext4_mb_release_inode_pa()
ext4: improve code readability in ext4_iget()
ext4: fix spectre gadget in ext4_mb_regular_allocator()
ext4: check for NUL characters in extended attribute's name
ext4: use ext4_warning() for sb_getblk failure
ext4: fix race when setting the bitmap corrupted flag
ext4: reset error code in ext4_find_entry in fallback
ext4: handle layout changes to pinned DAX mappings
dax: dax_layout_busy_page() warn on !exceptional
docs: fix up the obviously obsolete bits in the new ext4 documentation
docs: add new ext4 superblock time extension fields
docs: create filesystem internal section
ext4: use swap macro in mext_page_double_lock
ext4: check allocation failure when duplicating "data" in ext4_remount()
ext4: fix warning message in ext4_enable_quotas()
ext4: super: extend timestamps to 40 bits
jbd2: replace current_kernel_time64 with ktime equivalent
ext4: use timespec64 for all inode times
ext4: use ktime_get_real_seconds for i_dtime
ext4: use 64-bit timestamps for mmp_time
...
Diffstat (limited to 'Documentation/filesystems/ext4/ondisk/blocks.rst')
-rw-r--r-- | Documentation/filesystems/ext4/ondisk/blocks.rst | 142 |
1 files changed, 142 insertions, 0 deletions
diff --git a/Documentation/filesystems/ext4/ondisk/blocks.rst b/Documentation/filesystems/ext4/ondisk/blocks.rst new file mode 100644 index 000000000000..73d4dc0f7bda --- /dev/null +++ b/Documentation/filesystems/ext4/ondisk/blocks.rst @@ -0,0 +1,142 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Blocks +------ + +ext4 allocates storage space in units of “blocks”. A block is a group of +sectors between 1KiB and 64KiB, and the number of sectors must be an +integral power of 2. Blocks are in turn grouped into larger units called +block groups. Block size is specified at mkfs time and typically is +4KiB. You may experience mounting problems if block size is greater than +page size (i.e. 64KiB blocks on a i386 which only has 4KiB memory +pages). By default a filesystem can contain 2^32 blocks; if the '64bit' +feature is enabled, then a filesystem can have 2^64 blocks. + +For 32-bit filesystems, limits are as follows: + +.. list-table:: + :widths: 1 1 1 1 1 + :header-rows: 1 + + * - Item + - 1KiB + - 2KiB + - 4KiB + - 64KiB + * - Blocks + - 2^32 + - 2^32 + - 2^32 + - 2^32 + * - Inodes + - 2^32 + - 2^32 + - 2^32 + - 2^32 + * - File System Size + - 4TiB + - 8TiB + - 16TiB + - 256PiB + * - Blocks Per Block Group + - 8,192 + - 16,384 + - 32,768 + - 524,288 + * - Inodes Per Block Group + - 8,192 + - 16,384 + - 32,768 + - 524,288 + * - Block Group Size + - 8MiB + - 32MiB + - 128MiB + - 32GiB + * - Blocks Per File, Extents + - 2^32 + - 2^32 + - 2^32 + - 2^32 + * - Blocks Per File, Block Maps + - 16,843,020 + - 134,480,396 + - 1,074,791,436 + - 4,398,314,962,956 (really 2^32 due to field size limitations) + * - File Size, Extents + - 4TiB + - 8TiB + - 16TiB + - 256TiB + * - File Size, Block Maps + - 16GiB + - 256GiB + - 4TiB + - 256TiB + +For 64-bit filesystems, limits are as follows: + +.. list-table:: + :widths: 1 1 1 1 1 + :header-rows: 1 + + * - Item + - 1KiB + - 2KiB + - 4KiB + - 64KiB + * - Blocks + - 2^64 + - 2^64 + - 2^64 + - 2^64 + * - Inodes + - 2^32 + - 2^32 + - 2^32 + - 2^32 + * - File System Size + - 16ZiB + - 32ZiB + - 64ZiB + - 1YiB + * - Blocks Per Block Group + - 8,192 + - 16,384 + - 32,768 + - 524,288 + * - Inodes Per Block Group + - 8,192 + - 16,384 + - 32,768 + - 524,288 + * - Block Group Size + - 8MiB + - 32MiB + - 128MiB + - 32GiB + * - Blocks Per File, Extents + - 2^32 + - 2^32 + - 2^32 + - 2^32 + * - Blocks Per File, Block Maps + - 16,843,020 + - 134,480,396 + - 1,074,791,436 + - 4,398,314,962,956 (really 2^32 due to field size limitations) + * - File Size, Extents + - 4TiB + - 8TiB + - 16TiB + - 256TiB + * - File Size, Block Maps + - 16GiB + - 256GiB + - 4TiB + - 256TiB + +Note: Files not using extents (i.e. files using block maps) must be +placed within the first 2^32 blocks of a filesystem. Files with extents +must be placed within the first 2^48 blocks of a filesystem. It's not +clear what happens with larger filesystems. |