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Date: Mon, 28 Mar 2011 14:02:43 -0400
From: Oren Elrad <elrad@...ndeis.edu>
To: linux-ext4@...r.kernel.org
Subject: [PATCH] mke2fs reserved_ratio default value is nonsensical
Undesired behavior; mke2fs defaults to reserving 5% of the volume for
the root user. 5% of a 2TB volume is 100GB. The rationale for root
reservation (syslogd, etc...) does not require 100GB. As volumes get
larger, this default makes less and less sense.
Proposal; If the user does not specify their preferred reserve_ratio
on the command-line (-m), use the less of 5% or MAX_RSRV_SIZE. I
propose 10GiB as a sensible maximum default reservation for root.
Patch: Follows and http://capsid.brandeis.edu/~elrad/e2fsprog.gitdiff
Tested on the latest git+patch, RHEL5 (2.6.18-194.17.1.el5) with a
12TB volume (which would reserve 600GB under the default!):
# /root/e2fsprogs/misc/mke2fs -T ext4 -L scratch /dev/sdd1
[...]
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
732422144 inodes, 2929671159 blocks
2621440 blocks (0.09%) reserved for the super user
[...]
Oren Elrad
Dept. of Physics
Brandeis University
---- Patch follows ----
diff --git a/misc/mke2fs.c b/misc/mke2fs.c
index 9798b88..0ff3785 100644
--- a/misc/mke2fs.c
+++ b/misc/mke2fs.c
@@ -108,6 +108,8 @@ profile_t profile;
int sys_page_size = 4096;
int linux_version_code = 0;
+static const unsigned long long MAX_RSRV_SIZE = 10ULL * (1 << 30); // 10 GiB
+
static void usage(void)
{
fprintf(stderr, _("Usage: %s [-c|-l filename] [-b block-size] "
@@ -1154,7 +1156,7 @@ static void PRS(int argc, char *argv[])
int inode_ratio = 0;
int inode_size = 0;
unsigned long flex_bg_size = 0;
- double reserved_ratio = 5.0;
+ double reserved_ratio = -1.0; // Default: lesser of 5%, MAX_RSRV_SIZE
int lsector_size = 0, psector_size = 0;
int show_version_only = 0;
unsigned long long num_inodes = 0; /* unsigned long long to catch
too-large input */
@@ -1893,9 +1895,17 @@ profile_error:
/*
* Calculate number of blocks to reserve
+ * If reserved_ratio >= 0.0, it was passed as an argument, use it as-is
+ * If reserved_ratio < 0.0, no argument was passed, choose the
lesser of 5%, MAX_RSRV_SIZE
*/
- ext2fs_r_blocks_count_set(&fs_param, reserved_ratio *
- ext2fs_blocks_count(&fs_param) / 100.0);
+ if ( reserved_ratio >= 0.0 ) {
+ ext2fs_r_blocks_count_set(&fs_param, reserved_ratio *
+ ext2fs_blocks_count(&fs_param) / 100.0);
+ } else {
+ const blk64_t r_blk_count = ext2fs_blocks_count(&fs_param) / 20.0;
+ const blk64_t max_r_blk_count = MAX_RSRV_SIZE / blocksize;
+ ext2fs_r_blocks_count_set(&fs_param, (r_blk_count < max_r_blk_count
? r_blk_count : max_r_blk_count));
+ }
}
static int should_do_undo(const char *name)
By making a contribution to this project, I certify that:
(a) The contribution was created in whole or in part by me and I
have the right to submit it under the open source license
indicated in the file;
(d) I understand and agree that this project and the contribution
are public and that a record of the contribution (including all
personal information I submit with it, including my sign-off) is
maintained indefinitely and may be redistributed consistent with
this project or the open source license(s) involved.
Signed-off-by: Oren M Elrad <elrad@...ndeis.edu>
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