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authorJason Gunthorpe <jgg@mellanox.com>2018-08-16 22:13:03 +0200
committerJason Gunthorpe <jgg@mellanox.com>2018-08-16 22:21:29 +0200
commit0a3173a5f09bc58a3638ecfd0a80bdbae55e123c (patch)
treed6c0bc84863cca54dfbde3b7463e5d49c82af9f1 /Documentation/filesystems/ext4/ondisk/blocks.rst
parentRevert "net/smc: Replace ib_query_gid with rdma_get_gid_attr" (diff)
parentMerge tag 'for-linus-4.19-ofs1' of git://git.kernel.org/pub/scm/linux/kernel/... (diff)
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Merge branch 'linus/master' into rdma.git for-next
rdma.git merge resolution for the 4.19 merge window Conflicts: drivers/infiniband/core/rdma_core.c - Use the rdma code and revise with the new spelling for atomic_fetch_add_unless drivers/nvme/host/rdma.c - Replace max_sge with max_send_sge in new blk code drivers/nvme/target/rdma.c - Use the blk code and revise to use NULL for ib_post_recv when appropriate - Replace max_sge with max_recv_sge in new blk code net/rds/ib_send.c - Use the net code and revise to use NULL for ib_post_recv when appropriate Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
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+.. 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.