According to the mke2fs man page, the supported cluster-size values for an ext4 filesystem are 2048 to 256M bytes. However, this is not the case. When mkfs is run to create a filesystem with following specifications: * 1k blocksize and cluster-size greater than 32M * 2k blocksize and cluster-size greater than 64M * 4k blocksize and cluster-size greater than 128M mkfs fails with "Invalid argument passed to ext2 library while trying to create journal" error. In general, when the cluster-size to blocksize ratio is greater than 32k, mkfs fails with this error. Went through the code and found out that the function `ext2fs_new_range()` is the source of this error. This is because when the cluster-size to blocksize ratio exceeds 32k, the length argument to the function `ext2fs_new_range()` results in 0. Hence, the error. This patch corrects the valid cluster-size values. v2->v3: Remove redundant words and add info about how cluster-sizes that are not powers of 2 are rounded. --- misc/mke2fs.8.in | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/misc/mke2fs.8.in b/misc/mke2fs.8.in index 30f97bb5..c7b21f9d 100644 --- a/misc/mke2fs.8.in +++ b/misc/mke2fs.8.in @@ -232,9 +232,13 @@ test is used instead of a fast read-only test. .TP .B \-C " cluster-size" Specify the size of cluster in bytes for file systems using the bigalloc -feature. Valid cluster-size values are from 2048 to 256M bytes per -cluster. This can only be specified if the bigalloc feature is -enabled. (See the +feature. Valid cluster-size values range from 2 to 32768 times the +filesystem blocksize and must be a power of 2. If a cluster-size that is +not a power of 2 is provided, it will be rounded down to the nearest +power of 2 that is less than the given cluster-size. For example, +specifying '-C 20k', '-C 30k', or '-C 17k' will result in a cluster-size +of 16k. The cluster-size can only be specified if the +bigalloc feature is enabled. (See the .B ext4 (5) man page for more details about bigalloc.) The default cluster size if bigalloc is enabled is 16 times the block size. -- 2.39.3
