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Message-Id: <3016732A-E5AA-4EE7-980A-05323CD346A6@dilger.ca>
Date: Fri, 18 Aug 2017 12:45:21 -0600
From: Andreas Dilger <adilger@...ger.ca>
To: Theodore Ts'o <tytso@....edu>
Cc: Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] e2fsck: set dir_nlink feature if large dir exists
On Aug 18, 2017, at 12:19 PM, Andreas Dilger <adilger@...ger.ca> wrote:
>
> If there is a directory with more than EXT2_LINK_MAX (65000)
> subdirectories, but the DIR_NLINK feature is not set in the
> superblock, the feature should be set before continuing on
> to change the on-disk directory link count to 1.
>
> While most filesystems should have DIR_NLINK set (it was set
> by default for all ext4 filesystems, and the kernel before
> 4.12 automatically set it if the directory link count grew
> too large), it is possible that this flag is lost due to disk
> corruption or for an upgraded filesystem. We no longer want
> the kernel to automatically enable this feature.
>
> Addresses: https://bugzilla.kernel.org/show_bug.cgi?id=196405
> Signed-off-by: Andreas Dilger <adilger@...ger.ca>
> ---
Note that this is using the f_large_dir test for verification,
since it was already creating a directory with 48k entries in
it and already took ages to run because directory processing
in libext2fs is O(n^2) (it took about 2h to finish in my VM).
The alternative is storing a 100MB image file (though it may
be possible to compress it significantly).
I'm working on a patch to improve the debugfs "expand" command
so that it can insert multiple directory blocks at once, rather
than one-at-a-time (after a full directory scan). That at least
fixes half of the problem.
Cheers, Andreas
> e2fsck/pass4.c | 12 +++++++++-
> e2fsck/problem.c | 5 ++++
> e2fsck/problem.h | 3 +++
> tests/f_large_dir/expect | 7 ++++--
> tests/f_large_dir/script | 60 ++++++++++++++++++++++++++++++------------------
> 5 files changed, 62 insertions(+), 25 deletions(-)
>
> diff --git a/e2fsck/pass4.c b/e2fsck/pass4.c
> index 663f87a..d0ff8e9 100644
> --- a/e2fsck/pass4.c
> +++ b/e2fsck/pass4.c
> @@ -170,6 +170,7 @@ void e2fsck_pass4(e2fsck_t ctx)
> #endif
> struct problem_context pctx;
> __u16 link_count, link_counted;
> + int dir_nlink_fs;
> char *buf = 0;
> dgrp_t group, maxgroup;
>
> @@ -193,6 +194,8 @@ void e2fsck_pass4(e2fsck_t ctx)
> if (!(ctx->options & E2F_OPT_PREEN))
> fix_problem(ctx, PR_4_PASS_HEADER, &pctx);
>
> + dir_nlink_fs = ext2fs_has_feature_dir_nlink(fs->super);
> +
> group = 0;
> maxgroup = fs->group_desc_count;
> if (ctx->progress)
> @@ -249,8 +252,15 @@ void e2fsck_pass4(e2fsck_t ctx)
> &link_counted);
> }
> isdir = ext2fs_test_inode_bitmap2(ctx->inode_dir_map, i);
> - if (isdir && (link_counted > EXT2_LINK_MAX))
> + if (isdir && (link_counted > EXT2_LINK_MAX)) {
> + if (!dir_nlink_fs &&
> + fix_problem(ctx, PR_4_DIR_NLINK_FEATURE, &pctx)) {
> + ext2fs_set_feature_dir_nlink(fs->super);
> + ext2fs_mark_super_dirty(fs);
> + dir_nlink_fs = 1;
> + }
> link_counted = 1;
> + }
> if (link_counted != link_count) {
> e2fsck_read_inode_full(ctx, i, EXT2_INODE(inode),
> inode_size, "pass4");
> diff --git a/e2fsck/problem.c b/e2fsck/problem.c
> index 9706933..25c1de9 100644
> --- a/e2fsck/problem.c
> +++ b/e2fsck/problem.c
> @@ -1873,6 +1873,11 @@ static struct e2fsck_problem problem_table[] = {
> N_("@a @i %i ref count is %N, @s %n. "),
> PROMPT_FIX, PR_PREEN_OK },
>
> + /* directory exceeds max links, but no DIR_NLINK feature in superblock*/
> + { PR_4_DIR_NLINK_FEATURE,
> + N_("@d exceeds max links, but no DIR_NLINK feature in @S.\n"),
> + PROMPT_FIX, 0 },
> +
> /* Pass 5 errors */
>
> /* Pass 5: Checking group summary information */
> diff --git a/e2fsck/problem.h b/e2fsck/problem.h
> index f30f8f0..07ed0a7 100644
> --- a/e2fsck/problem.h
> +++ b/e2fsck/problem.h
> @@ -1134,6 +1134,9 @@ struct problem_context {
> /* Extended attribute inode ref count wrong */
> #define PR_4_EA_INODE_REF_COUNT 0x040005
>
> +/* directory exceeds max links, but no DIR_NLINK feature in superblock */
> +#define PR_4_DIR_NLINK_FEATURE 0x040006
> +
> /*
> * Pass 5 errors
> */
> diff --git a/tests/f_large_dir/expect b/tests/f_large_dir/expect
> index b099460..4b9ca6f 100644
> --- a/tests/f_large_dir/expect
> +++ b/tests/f_large_dir/expect
> @@ -3,10 +3,13 @@ Pass 2: Checking directory structure
> Pass 3: Checking directory connectivity
> Pass 3A: Optimizing directories
> Pass 4: Checking reference counts
> -Inode 13 ref count is 1, should be 47245. Fix? yes
> +Directory exceeds max links, but no DIR_NLINK feature in superblock.
> +Fix? yes
> +
> +Inode 12 ref count is 65012, should be 1. Fix? yes
>
> Pass 5: Checking group summary information
>
> test.img: ***** FILE SYSTEM WAS MODIFIED *****
> -test.img: 13/115368 files (0.0% non-contiguous), 32817/460800 blocks
> +test.img: 65023/65104 files (0.0% non-contiguous), 96668/100937 blocks
> Exit status is 1
> diff --git a/tests/f_large_dir/script b/tests/f_large_dir/script
> index 0b5fdff..a10fe16 100644
> --- a/tests/f_large_dir/script
> +++ b/tests/f_large_dir/script
> @@ -5,43 +5,59 @@ E2FSCK=../e2fsck/e2fsck
> NAMELEN=255
> DIRENT_SZ=8
> BLOCKSZ=1024
> +INODESZ=128
> DIRENT_PER_LEAF=$((BLOCKSZ / (NAMELEN + DIRENT_SZ)))
> HEADER=32
> INDEX_SZ=8
> INDEX_L1=$(((BLOCKSZ - HEADER) / INDEX_SZ))
> INDEX_L2=$(((BLOCKSZ - DIRENT_SZ) / INDEX_SZ))
> ENTRIES=$((INDEX_L1 * INDEX_L2 * DIRENT_PER_LEAF))
> +DIRBLK=$((2 + INDEX_L1 * INDEX_L2))
> +EXT4_LINK_MAX=65000
> +[ $ENTRIES -lt $((EXT4_LINK_MAX + 10)) ] && ENTRIES=$((EXT4_LINK_MAX + 10))
> +FSIZE=$(((DIRBLK + EXT4_LINK_MAX * ((BLOCKSZ + INODESZ) / BLOCKSZ)) * 5 / 4))
>
> -cp /dev/null $OUT
> -$MKE2FS -b 1024 -O large_dir,uninit_bg,dir_nlink -F $TMPFILE 460800 \
> - > /dev/null 2>&1
> +> $OUT
> +$MKE2FS -b 1024 -O large_dir,uninit_bg -N $((ENTRIES + 50)) \
> + -I $INODESZ -F $TMPFILE $FSIZE > $OUT 2>&1
> +RC=$?
> +if [ $RC -eq 0 ]; then
> {
> - echo "feature large_dir"
> + START=$SECONDS
> echo "mkdir /foo"
> echo "cd /foo"
> - touch foofile
> - echo "write foofile foofile"
> + touch $TMPFILE.tmp
> + echo "write $TMPFILE.tmp foofile"
> i=0
> - while test $i -lt $ENTRIES ; do
> - if test $(( i % DIRENT_PER_LEAF )) -eq 0 ; then
> - echo "expand ./"
> + while test $i -lt $ENTRIES ; do
> + if test $((i % DIRENT_PER_LEAF)) -eq 0; then
> + echo "expand ./"
> fi
> - if test $(( i % 5000 )) -eq 0 -a $i -gt 0 ; then
> - >&2 echo "$test_name: $i processed"
> + if test $((i % 5000)) -eq 0 -a $i -gt 0; then
> + ELAPSED=$((SECONDS - START))
> + RATE=$((i / ELAPSED))
> + >&2 echo "$test_name: $i processed in ${ELAPSED}s @ $RATE/s"
> fi
> - printf "ln foofile %0255X\n" $i
> - i=$(($i + 1))
> + if test $i -lt $((EXT4_LINK_MAX + 10)); then
> + printf "mkdir d%0254u\n" $i
> + else
> + printf "ln foofile f%0254u\n" $i
> + fi
> + i=$((i + 1))
> done
> -} | $DEBUGFS -w -f /dev/stdin $TMPFILE > /dev/null 2>&1
> -
> -$E2FSCK -yfD $TMPFILE > $OUT.new 2>&1
> -status=$?
> -echo Exit status is $status >> $OUT.new
> -sed -f $cmd_dir/filter.sed -e "s;$TMPFILE;test.img;" $OUT.new >> $OUT
> -rm -f $OUT.new
> +} | $DEBUGFS -w -f /dev/stdin $TMPFILE > $OUT
> + RC=$?
> +fi
> +if [ $RC -eq 0 ]; then
> + $E2FSCK -yfD $TMPFILE > $OUT.new 2>&1
> + status=$?
> + echo "Exit status is $status" >> $OUT.new
> + sed -f $cmd_dir/filter.sed -e "s;$TMPFILE;test.img;" $OUT.new > $OUT
> + rm -f $OUT.new
>
> -cmp -s $OUT $EXP
> -RC=$?
> + cmp -s $OUT $EXP
> + RC=$?
> +fi
> if [ $RC -eq 0 ]; then
> echo "$test_name: $test_description: ok"
> touch $test_name.ok
> --
> 1.8.0
>
Cheers, Andreas
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