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Message-ID: <20150406185737.GM5519@birch.djwong.org>
Date: Mon, 6 Apr 2015 11:57:37 -0700
From: "Darrick J. Wong" <darrick.wong@...cle.com>
To: Andreas Dilger <adilger@...ger.ca>
Cc: linux-ext4 <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH 09/35] e2fsck: abort on read error beyond end of FS
On Fri, Apr 03, 2015 at 03:11:39PM -0600, Andreas Dilger wrote:
> On Apr 2, 2015, at 12:00 AM, Darrick J. Wong <darrick.wong@...cle.com> wrote:
> > On Wed, Apr 01, 2015 at 11:10:48PM -0500, Andreas Dilger wrote:
> >> It isn't clear what the benefit of this patch is? There are times (e.g.
> >> if a partition table is broken or if a single-disk filesystem is changed
> >> to an MD RAID device) that it is useful to run e2fsck on such a
> >> filesystem.
> >>
> >> With this patch, it's essentially turning a small error into a fatal one,
> >> but what is the benefit?
> >
> > This came from a debugging patch I was using to see if I could trick fsck
> > into using garbage values when it tries to "fix" things.
> >
> > I'm not really sure what the usage scenario is for running fsck on a FS
> > that's too big for the device containing it -- wouldn't you want fsck to
> > stop immediately?
>
> As mentioned above, this can happen in some cases, and e2fsck already has
> a check for it and it will prompt to abort:
>
> { PR_0_FS_SIZE_WRONG,
> N_("The @f size (according to the @S) is %b @bs\n"
> "The physical size of the @v is %c @bs\n"
> "Either the @S or the partition table is likely to be corrupt!\n"),
> PROMPT_ABORT, 0 },
>
> However, it doesn't _force_ e2fsck to abort, because someone might want to
> be able to recover from such a situation (e.g. lose a few files that use
> blocks beyond the end of the device) rather than have an unusable filesystem.
Yeah, you're probably right, this is at best a debugging patch. Let's drop it.
--D
>
> Cheers, Andreas
>
> > --D
> >
> >>
> >> Cheers, Andreas
> >>
> >>> On Apr 1, 2015, at 21:35, Darrick J. Wong <darrick.wong@...cle.com> wrote:
> >>>
> >>> Abort if we fail to read a block that's past the end of the FS.
> >>> Includes a flag to disable the abort behavior for selected parts of
> >>> the fsck run, so that we don't fail on a busted object prior to fixing
> >>> it.
> >>>
> >>> Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
> >>> ---
> >>> e2fsck/e2fsck.h | 1 +
> >>> e2fsck/ehandler.c | 7 +++++--
> >>> e2fsck/extents.c | 2 ++
> >>> e2fsck/journal.c | 3 +++
> >>> e2fsck/message.c | 12 +++++++++++-
> >>> e2fsck/pass1.c | 28 ++++++++++++++++------------
> >>> e2fsck/pass1b.c | 4 ++++
> >>> 7 files changed, 42 insertions(+), 15 deletions(-)
> >>>
> >>>
> >>> diff --git a/e2fsck/e2fsck.h b/e2fsck/e2fsck.h
> >>> index 5fda863..453b552 100644
> >>> --- a/e2fsck/e2fsck.h
> >>> +++ b/e2fsck/e2fsck.h
> >>> @@ -193,6 +193,7 @@ struct resource_track {
> >>> #define E2F_FLAG_TIME_INSANE 0x2000 /* Time is insane */
> >>> #define E2F_FLAG_PROBLEMS_FIXED 0x4000 /* At least one problem was fixed */
> >>> #define E2F_FLAG_ALLOC_OK 0x8000 /* Can we allocate blocks? */
> >>> +#define E2F_FLAG_IGNORE_READ_ERROR 0x10000 /* Don't rewrite read error blocks */
> >>>
> >>> #define E2F_RESET_FLAGS (E2F_FLAG_TIME_INSANE | E2F_FLAG_PROBLEMS_FIXED)
> >>>
> >>> diff --git a/e2fsck/ehandler.c b/e2fsck/ehandler.c
> >>> index 71ca301..847f8e5 100644
> >>> --- a/e2fsck/ehandler.c
> >>> +++ b/e2fsck/ehandler.c
> >>> @@ -60,8 +60,11 @@ static errcode_t e2fsck_handle_read_error(io_channel channel,
> >>> preenhalt(ctx);
> >>>
> >>> /* Don't rewrite a block past the end of the FS. */
> >>> - if (block >= ext2fs_blocks_count(fs->super))
> >>> - return 0;
> >>> + if (block >= ext2fs_blocks_count(fs->super)) {
> >>> + if (ctx->flags & E2F_FLAG_IGNORE_READ_ERROR)
> >>> + return 0;
> >>> + abort();
> >>> + }
> >>>
> >>> if (ask(ctx, _("Ignore error"), 1)) {
> >>> if (ask(ctx, _("Force rewrite"), 1))
> >>> diff --git a/e2fsck/extents.c b/e2fsck/extents.c
> >>> index 8465299..cff265a 100644
> >>> --- a/e2fsck/extents.c
> >>> +++ b/e2fsck/extents.c
> >>> @@ -29,6 +29,7 @@ errcode_t e2fsck_rebuild_extents_later(e2fsck_t ctx, ext2_ino_t ino)
> >>> {
> >>> if (!EXT2_HAS_INCOMPAT_FEATURE(ctx->fs->super,
> >>> EXT3_FEATURE_INCOMPAT_EXTENTS) ||
> >>> + (ctx->flags & (E2F_FLAG_RESTART_LATER | E2F_FLAG_RESTART)) ||
> >>> (ctx->options & E2F_OPT_NO) ||
> >>> (ino != EXT2_ROOT_INO && ino < ctx->fs->super->s_first_ino))
> >>> return 0;
> >>> @@ -339,6 +340,7 @@ static void rebuild_extents(e2fsck_t ctx, const char *pass_name, int pr_header)
> >>>
> >>> if (!EXT2_HAS_INCOMPAT_FEATURE(ctx->fs->super,
> >>> EXT3_FEATURE_INCOMPAT_EXTENTS) ||
> >>> + (ctx->flags & (E2F_FLAG_RESTART_LATER | E2F_FLAG_RESTART)) ||
> >>> !ext2fs_test_valid(ctx->fs) ||
> >>> ctx->invalid_bitmaps) {
> >>> if (ctx->inodes_to_rebuild)
> >>> diff --git a/e2fsck/journal.c b/e2fsck/journal.c
> >>> index 9f32095..c195797 100644
> >>> --- a/e2fsck/journal.c
> >>> +++ b/e2fsck/journal.c
> >>> @@ -315,6 +315,7 @@ static errcode_t e2fsck_get_journal(e2fsck_t ctx, journal_t **ret_journal)
> >>> journal->j_inode = NULL;
> >>> journal->j_blocksize = ctx->fs->blocksize;
> >>>
> >>> + ctx->flags |= E2F_FLAG_IGNORE_READ_ERROR;
> >>> if (uuid_is_null(sb->s_journal_uuid)) {
> >>> if (!sb->s_journal_inum) {
> >>> retval = EXT2_ET_BAD_INODE_NUM;
> >>> @@ -518,9 +519,11 @@ static errcode_t e2fsck_get_journal(e2fsck_t ctx, journal_t **ret_journal)
> >>>
> >>> *ret_journal = journal;
> >>> e2fsck_use_inode_shortcuts(ctx, 0);
> >>> + ctx->flags &= ~E2F_FLAG_IGNORE_READ_ERROR;
> >>> return 0;
> >>>
> >>> errout:
> >>> + ctx->flags &= ~E2F_FLAG_IGNORE_READ_ERROR;
> >>> e2fsck_use_inode_shortcuts(ctx, 0);
> >>> if (dev_fs)
> >>> ext2fs_free_mem(&dev_fs);
> >>> diff --git a/e2fsck/message.c b/e2fsck/message.c
> >>> index 9c1433f..510f291 100644
> >>> --- a/e2fsck/message.c
> >>> +++ b/e2fsck/message.c
> >>> @@ -199,14 +199,24 @@ static void print_pathname(FILE *f, ext2_filsys fs, ext2_ino_t dir,
> >>> {
> >>> errcode_t retval = 0;
> >>> char *path;
> >>> + e2fsck_t ctx = fs ? (e2fsck_t) fs->priv_data : NULL;
> >>> + int flags;
> >>>
> >>> if (!dir && (ino < num_special_inodes)) {
> >>> fputs(_(special_inode_name[ino]), f);
> >>> return;
> >>> }
> >>>
> >>> - if (fs)
> >>> + if (fs) {
> >>> + if (ctx) {
> >>> + flags = ctx->flags;
> >>> + ctx->flags |= E2F_FLAG_IGNORE_READ_ERROR;
> >>> + }
> >>> retval = ext2fs_get_pathname(fs, dir, ino, &path);
> >>> + if (ctx)
> >>> + ctx->flags &= ~E2F_FLAG_IGNORE_READ_ERROR |
> >>> + (flags & E2F_FLAG_IGNORE_READ_ERROR);
> >>> + }
> >>> if (!fs || retval)
> >>> fputs("???", f);
> >>> else {
> >>> diff --git a/e2fsck/pass1.c b/e2fsck/pass1.c
> >>> index 308a95a..760fbde 100644
> >>> --- a/e2fsck/pass1.c
> >>> +++ b/e2fsck/pass1.c
> >>> @@ -510,6 +510,7 @@ static void check_is_really_dir(e2fsck_t ctx, struct problem_context *pctx,
> >>> int extent_fs;
> >>> int inlinedata_fs;
> >>>
> >>> + ctx->flags |= E2F_FLAG_IGNORE_READ_ERROR;
> >>> /*
> >>> * If the mode looks OK, we believe it. If the first block in
> >>> * the i_block array is 0, this cannot be a directory. If the
> >>> @@ -519,7 +520,7 @@ static void check_is_really_dir(e2fsck_t ctx, struct problem_context *pctx,
> >>> */
> >>> if (LINUX_S_ISDIR(inode->i_mode) || LINUX_S_ISREG(inode->i_mode) ||
> >>> LINUX_S_ISLNK(inode->i_mode) || inode->i_block[0] == 0)
> >>> - return;
> >>> + goto out;
> >>>
> >>> /*
> >>> * Check the block numbers in the i_block array for validity:
> >>> @@ -552,13 +553,13 @@ static void check_is_really_dir(e2fsck_t ctx, struct problem_context *pctx,
> >>> struct ext2_dir_entry de;
> >>>
> >>> if (ext2fs_inline_data_size(ctx->fs, pctx->ino, &size))
> >>> - return;
> >>> + goto out;
> >>> /*
> >>> * If the size isn't a multiple of 4, it's probably not a
> >>> * directory??
> >>> */
> >>> if (size & 3)
> >>> - return;
> >>> + goto out;
> >>> /*
> >>> * If the first 10 bytes don't look like a directory entry,
> >>> * it's probably not a directory.
> >>> @@ -578,14 +579,14 @@ static void check_is_really_dir(e2fsck_t ctx, struct problem_context *pctx,
> >>> de.inode != 0) ||
> >>> rec_len > EXT4_MIN_INLINE_DATA_SIZE -
> >>> EXT4_INLINE_DATA_DOTDOT_SIZE)
> >>> - return;
> >>> + goto out;
> >>> /* device files never have a "system.data" entry */
> >>> goto isdir;
> >>> } else if (extent_fs && (inode->i_flags & EXT4_EXTENTS_FL)) {
> >>> /* extent mapped */
> >>> if (ext2fs_bmap2(ctx->fs, pctx->ino, inode, 0, 0, 0, 0,
> >>> &blk))
> >>> - return;
> >>> + goto out;
> >>> /* device files are never extent mapped */
> >>> not_device++;
> >>> } else {
> >>> @@ -600,7 +601,7 @@ static void check_is_really_dir(e2fsck_t ctx, struct problem_context *pctx,
> >>> blk >= ext2fs_blocks_count(ctx->fs->super) ||
> >>> ext2fs_fast_test_block_bitmap2(ctx->block_found_map,
> >>> blk))
> >>> - return; /* Invalid block, can't be dir */
> >>> + goto out; /* Invalid block, can't be dir */
> >>> }
> >>> blk = inode->i_block[0];
> >>> }
> >>> @@ -612,45 +613,48 @@ static void check_is_really_dir(e2fsck_t ctx, struct problem_context *pctx,
> >>> */
> >>> if ((LINUX_S_ISCHR(inode->i_mode) || LINUX_S_ISBLK(inode->i_mode)) &&
> >>> (inode->i_links_count == 1) && !not_device)
> >>> - return;
> >>> + goto out;
> >>>
> >>> /* read the first block */
> >>> ehandler_operation(_("reading directory block"));
> >>> retval = ext2fs_read_dir_block4(ctx->fs, blk, buf, 0, pctx->ino);
> >>> ehandler_operation(0);
> >>> if (retval)
> >>> - return;
> >>> + goto out;
> >>>
> >>> dirent = (struct ext2_dir_entry *) buf;
> >>> retval = ext2fs_get_rec_len(ctx->fs, dirent, &rec_len);
> >>> if (retval)
> >>> - return;
> >>> + goto out;
> >>> if ((ext2fs_dirent_name_len(dirent) != 1) ||
> >>> (dirent->name[0] != '.') ||
> >>> (dirent->inode != pctx->ino) ||
> >>> (rec_len < 12) ||
> >>> (rec_len % 4) ||
> >>> (rec_len >= ctx->fs->blocksize - 12))
> >>> - return;
> >>> + goto out;
> >>>
> >>> dirent = (struct ext2_dir_entry *) (buf + rec_len);
> >>> retval = ext2fs_get_rec_len(ctx->fs, dirent, &rec_len);
> >>> if (retval)
> >>> - return;
> >>> + goto out;
> >>> if ((ext2fs_dirent_name_len(dirent) != 2) ||
> >>> (dirent->name[0] != '.') ||
> >>> (dirent->name[1] != '.') ||
> >>> (rec_len < 12) ||
> >>> (rec_len % 4))
> >>> - return;
> >>> + goto out;
> >>>
> >>> isdir:
> >>> + ctx->flags &= ~E2F_FLAG_IGNORE_READ_ERROR;
> >>> if (fix_problem(ctx, PR_1_TREAT_AS_DIRECTORY, pctx)) {
> >>> inode->i_mode = (inode->i_mode & 07777) | LINUX_S_IFDIR;
> >>> e2fsck_write_inode_full(ctx, pctx->ino, inode,
> >>> EXT2_INODE_SIZE(ctx->fs->super),
> >>> "check_is_really_dir");
> >>> }
> >>> +out:
> >>> + ctx->flags &= ~E2F_FLAG_IGNORE_READ_ERROR;
> >>> }
> >>>
> >>> void e2fsck_setup_tdb_icount(e2fsck_t ctx, int flags,
> >>> diff --git a/e2fsck/pass1b.c b/e2fsck/pass1b.c
> >>> index cd967f4..10136a6 100644
> >>> --- a/e2fsck/pass1b.c
> >>> +++ b/e2fsck/pass1b.c
> >>> @@ -234,7 +234,9 @@ void e2fsck_pass1_dupblocks(e2fsck_t ctx, char *block_buf)
> >>> dict_set_allocator(&clstr_dict, NULL, cluster_dnode_free, NULL);
> >>>
> >>> init_resource_track(&rtrack, ctx->fs->io);
> >>> + ctx->flags |= E2F_FLAG_IGNORE_READ_ERROR;
> >>> pass1b(ctx, block_buf);
> >>> + ctx->flags &= ~E2F_FLAG_IGNORE_READ_ERROR;
> >>> print_resource_track(ctx, "Pass 1b", &rtrack, ctx->fs->io);
> >>>
> >>> init_resource_track(&rtrack, ctx->fs->io);
> >>> @@ -242,7 +244,9 @@ void e2fsck_pass1_dupblocks(e2fsck_t ctx, char *block_buf)
> >>> print_resource_track(ctx, "Pass 1c", &rtrack, ctx->fs->io);
> >>>
> >>> init_resource_track(&rtrack, ctx->fs->io);
> >>> + ctx->flags |= E2F_FLAG_IGNORE_READ_ERROR;
> >>> pass1d(ctx, block_buf);
> >>> + ctx->flags &= ~E2F_FLAG_IGNORE_READ_ERROR;
> >>> print_resource_track(ctx, "Pass 1d", &rtrack, ctx->fs->io);
> >>>
> >>> /*
> >>>
> >>> --
> >>> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
> >>> the body of a message to majordomo@...r.kernel.org
> >>> More majordomo info at http://vger.kernel.org/majordomo-info.html
> >> --
> >> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
> >> the body of a message to majordomo@...r.kernel.org
> >> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
>
> Cheers, Andreas
>
>
>
>
>
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