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Date: Wed, 3 Aug 2022 09:00:01 +0200 From: Lukas Czerner <lczerner@...hat.com> To: Josh Triplett <josh@...htriplett.org> Cc: Theodore Ts'o <tytso@....edu>, Andreas Dilger <adilger.kernel@...ger.ca>, linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] ext4: Don't run ext4lazyinit for read-only filesystems On Sun, Jul 31, 2022 at 08:24:53PM -0700, Josh Triplett wrote: > On a read-only filesystem, we won't invoke the block allocator, so we > don't need to prefetch the block bitmaps. > > This avoids starting and running the ext4lazyinit thread at all on a > system with no read-write ext4 filesystems (for instance, a container VM > with read-only filesystems underneath an overlayfs). > > Fixes: 21175ca434c5 ("ext4: make prefetch_block_bitmaps default") > Signed-off-by: Josh Triplett <josh@...htriplett.org> > --- Looks good to me. Reviewed-by: Lukas Czerner <lczerner@...hat.com> > > Tested in a VM, with a read-only ext4 root filesystem. Confirmed that > ext4lazyinit starts without this patch, and does not start with this > patch. > > (For a future merge window, not the current one. Please let me know if I > need to re-send this at a later, more convenient time.) > > fs/ext4/super.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/fs/ext4/super.c b/fs/ext4/super.c > index 845f2f8aee5f..20437acc8865 100644 > --- a/fs/ext4/super.c > +++ b/fs/ext4/super.c > @@ -3973,9 +3973,9 @@ int ext4_register_li_request(struct super_block *sb, > goto out; > } > > - if (test_opt(sb, NO_PREFETCH_BLOCK_BITMAPS) && > - (first_not_zeroed == ngroups || sb_rdonly(sb) || > - !test_opt(sb, INIT_INODE_TABLE))) > + if (sb_rdonly(sb) || > + (test_opt(sb, NO_PREFETCH_BLOCK_BITMAPS) && > + (first_not_zeroed == ngroups || !test_opt(sb, INIT_INODE_TABLE)))) > goto out; > > elr = ext4_li_request_new(sb, first_not_zeroed); > -- > 2.36.1 >
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