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From 2831f4202dd1bec289a9a3459d553fcffda0f280 Mon Sep 17 00:00:00 2001
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From: Theodore Ts'o <tytso@mit.edu>
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Date: Sun, 18 Jul 2021 09:15:28 -0400
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Subject: [PATCH 34/46] mke2fs: only try discarding a single block to test if
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discard works
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Content-Type: text/plain
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Commit d2bfdc7ff15c ("Use punch hole as "discard" on regular files")
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added a test to see if the storage device actually supports discard.
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The intent was to try discarding the first block but since
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io_channel_discard() interprets the offset and count arguments in
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blocks, and not bytes, mke2fs was actually discarding the first 16
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megabytes (when the block size is 4k). This is normally not a
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problem, since most file systems are larger than that, and requests to
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discard beyond the end of the block device are ignored.
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However, when creating a small file system as part of a image
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containing multiple partitions, the initial test discard can end up
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discarding data beyond the file system being created.
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Addresses-Debian-Bug: #989630
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Reported-by: Josh Triplett <josh@joshtriplett.org>
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Fixes: d2bfdc7ff15c ("Use punch hole as "discard" on regular files")
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Signed-off-by: Theodore Ts'o <tytso@mit.edu>
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Signed-off-by: Lukas Czerner <lczerner@redhat.com>
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---
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misc/mke2fs.c | 5 ++---
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1 file changed, 2 insertions(+), 3 deletions(-)
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diff --git a/misc/mke2fs.c b/misc/mke2fs.c
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index 389d0981..b2bb2847 100644
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--- a/misc/mke2fs.c
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+++ b/misc/mke2fs.c
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@@ -2768,7 +2768,7 @@ static int mke2fs_discard_device(ext2_filsys fs)
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struct ext2fs_numeric_progress_struct progress;
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blk64_t blocks = ext2fs_blocks_count(fs->super);
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blk64_t count = DISCARD_STEP_MB;
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- blk64_t cur;
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+ blk64_t cur = 0;
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int retval = 0;
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/*
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@@ -2776,10 +2776,9 @@ static int mke2fs_discard_device(ext2_filsys fs)
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* we do not print numeric progress resulting in failure
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* afterwards.
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*/
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- retval = io_channel_discard(fs->io, 0, fs->blocksize);
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+ retval = io_channel_discard(fs->io, 0, 1);
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if (retval)
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return retval;
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- cur = fs->blocksize;
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count *= (1024 * 1024);
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count /= fs->blocksize;
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--
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2.35.1
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