Patchwork [10/31] libext2fs: Allow callers to punch a single block

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Submitter Darrick J. Wong
Date Oct. 1, 2013, 1:27 a.m.
Message ID <20131001012746.28415.15964.stgit@birch.djwong.org>
Download mbox | patch
Permalink /patch/279289/
State Accepted
Headers show

Comments

Darrick J. Wong - Oct. 1, 2013, 1:27 a.m.
The range of blocks to punch is treated as an inclusive range on both ends,
i.e. if start=1 and end=2, both blocks 1 and 2 are punched out.  Thus, start ==
end means that the caller wishes to punch a single block.  Remove the check
that prevents us from punching a single block.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 lib/ext2fs/ext2fs.h |    4 ++++
 lib/ext2fs/punch.c  |    5 +----
 2 files changed, 5 insertions(+), 4 deletions(-)



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jon ernst - Oct. 1, 2013, 7:09 p.m.
On Mon, Sep 30, 2013 at 9:27 PM, Darrick J. Wong
<darrick.wong@oracle.com> wrote:
> The range of blocks to punch is treated as an inclusive range on both ends,
> i.e. if start=1 and end=2, both blocks 1 and 2 are punched out.  Thus, start ==
> end means that the caller wishes to punch a single block.  Remove the check
> that prevents us from punching a single block.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---
>  lib/ext2fs/ext2fs.h |    4 ++++
>  lib/ext2fs/punch.c  |    5 +----
>  2 files changed, 5 insertions(+), 4 deletions(-)
>
>
> diff --git a/lib/ext2fs/ext2fs.h b/lib/ext2fs/ext2fs.h
> index 311ceda..c37e00b 100644
> --- a/lib/ext2fs/ext2fs.h
> +++ b/lib/ext2fs/ext2fs.h
> @@ -1385,6 +1385,10 @@ extern errcode_t ext2fs_check_mount_point(const char *device, int *mount_flags,
>                                           char *mtpt, int mtlen);
>
>  /* punch.c */
> +/*
> + * NOTE: This function removes from an inode the blocks "start", "end", and
> + * every block in between.
> + */
>  extern errcode_t ext2fs_punch(ext2_filsys fs, ext2_ino_t ino,
>                               struct ext2_inode *inode,
>                               char *block_buf, blk64_t start,
> diff --git a/lib/ext2fs/punch.c b/lib/ext2fs/punch.c
> index 11c7668..aac1942 100644
> --- a/lib/ext2fs/punch.c
> +++ b/lib/ext2fs/punch.c
> @@ -315,9 +315,6 @@ extern errcode_t ext2fs_punch(ext2_filsys fs, ext2_ino_t ino,
>         if (start > end)
>                 return EINVAL;
>
> -       if (start == end)
> -               return 0;
> -
>         /* Read inode structure if necessary */
>         if (!inode) {
>                 retval = ext2fs_read_inode(fs, ino, &inode_buf);
> @@ -332,7 +329,7 @@ extern errcode_t ext2fs_punch(ext2_filsys fs, ext2_ino_t ino,
>
>                 if (start > ~0U)
>                         return 0;
> -               count = ((end - start) < ~0U) ? (end - start) : ~0U;
> +               count = ((end - start + 1) < ~0U) ? (end - start + 1) : ~0U;
can you simply put "count =  end - start + 1;" since you have checked
start > end case earlier.
>                 retval = ext2fs_punch_ind(fs, inode, block_buf,
>                                           (blk_t) start, count);
>         }
>
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Darrick J. Wong - Oct. 1, 2013, 9:25 p.m.
On Tue, Oct 01, 2013 at 03:09:44PM -0400, jon ernst wrote:
> On Mon, Sep 30, 2013 at 9:27 PM, Darrick J. Wong
> <darrick.wong@oracle.com> wrote:
> > The range of blocks to punch is treated as an inclusive range on both ends,
> > i.e. if start=1 and end=2, both blocks 1 and 2 are punched out.  Thus, start ==
> > end means that the caller wishes to punch a single block.  Remove the check
> > that prevents us from punching a single block.
> >
> > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> > ---
> >  lib/ext2fs/ext2fs.h |    4 ++++
> >  lib/ext2fs/punch.c  |    5 +----
> >  2 files changed, 5 insertions(+), 4 deletions(-)
> >
> >
> > diff --git a/lib/ext2fs/ext2fs.h b/lib/ext2fs/ext2fs.h
> > index 311ceda..c37e00b 100644
> > --- a/lib/ext2fs/ext2fs.h
> > +++ b/lib/ext2fs/ext2fs.h
> > @@ -1385,6 +1385,10 @@ extern errcode_t ext2fs_check_mount_point(const char *device, int *mount_flags,
> >                                           char *mtpt, int mtlen);
> >
> >  /* punch.c */
> > +/*
> > + * NOTE: This function removes from an inode the blocks "start", "end", and
> > + * every block in between.
> > + */
> >  extern errcode_t ext2fs_punch(ext2_filsys fs, ext2_ino_t ino,
> >                               struct ext2_inode *inode,
> >                               char *block_buf, blk64_t start,
> > diff --git a/lib/ext2fs/punch.c b/lib/ext2fs/punch.c
> > index 11c7668..aac1942 100644
> > --- a/lib/ext2fs/punch.c
> > +++ b/lib/ext2fs/punch.c
> > @@ -315,9 +315,6 @@ extern errcode_t ext2fs_punch(ext2_filsys fs, ext2_ino_t ino,
> >         if (start > end)
> >                 return EINVAL;
> >
> > -       if (start == end)
> > -               return 0;
> > -
> >         /* Read inode structure if necessary */
> >         if (!inode) {
> >                 retval = ext2fs_read_inode(fs, ino, &inode_buf);
> > @@ -332,7 +329,7 @@ extern errcode_t ext2fs_punch(ext2_filsys fs, ext2_ino_t ino,
> >
> >                 if (start > ~0U)
> >                         return 0;
> > -               count = ((end - start) < ~0U) ? (end - start) : ~0U;
> > +               count = ((end - start + 1) < ~0U) ? (end - start + 1) : ~0U;
> can you simply put "count =  end - start + 1;" since you have checked
> start > end case earlier.

No.  This statement clamps 'count' at 2^32-1 (since the highest block number in
a non-extent file is 4294967295), which is necessary if the 'start' and 'end'
arguments are > 32bit arguments.  That happens in the truncate case of
ext2fs_file_set_size2().

For example, if end=0x100000080 and start=0x80, end-start+1 = 1, which is not
the behavior that we want.

For the record, if end=~0ULL and start=0, this also ensures that count=~0U.

--D

> >                 retval = ext2fs_punch_ind(fs, inode, block_buf,
> >                                           (blk_t) start, count);
> >         }
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
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Theodore Ts'o - Oct. 7, 2013, 1:40 p.m.
On Mon, Sep 30, 2013 at 06:27:46PM -0700, Darrick J. Wong wrote:
> The range of blocks to punch is treated as an inclusive range on both ends,
> i.e. if start=1 and end=2, both blocks 1 and 2 are punched out.  Thus, start ==
> end means that the caller wishes to punch a single block.  Remove the check
> that prevents us from punching a single block.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

Thanks, applied to the maint branch, modulo commit description
reformat.

		 	       		   - Ted
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Theodore Ts'o - Oct. 8, 2013, 3:54 p.m.
On Mon, Sep 30, 2013 at 06:27:46PM -0700, Darrick J. Wong wrote:
> The range of blocks to punch is treated as an inclusive range on both ends,
> i.e. if start=1 and end=2, both blocks 1 and 2 are punched out.  Thus, start ==
> end means that the caller wishes to punch a single block.  Remove the check
> that prevents us from punching a single block.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

Applied, thanks.

					- Ted
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Patch

diff --git a/lib/ext2fs/ext2fs.h b/lib/ext2fs/ext2fs.h
index 311ceda..c37e00b 100644
--- a/lib/ext2fs/ext2fs.h
+++ b/lib/ext2fs/ext2fs.h
@@ -1385,6 +1385,10 @@  extern errcode_t ext2fs_check_mount_point(const char *device, int *mount_flags,
 					  char *mtpt, int mtlen);
 
 /* punch.c */
+/*
+ * NOTE: This function removes from an inode the blocks "start", "end", and
+ * every block in between.
+ */
 extern errcode_t ext2fs_punch(ext2_filsys fs, ext2_ino_t ino,
 			      struct ext2_inode *inode,
 			      char *block_buf, blk64_t start,
diff --git a/lib/ext2fs/punch.c b/lib/ext2fs/punch.c
index 11c7668..aac1942 100644
--- a/lib/ext2fs/punch.c
+++ b/lib/ext2fs/punch.c
@@ -315,9 +315,6 @@  extern errcode_t ext2fs_punch(ext2_filsys fs, ext2_ino_t ino,
 	if (start > end)
 		return EINVAL;
 
-	if (start == end)
-		return 0;
-
 	/* Read inode structure if necessary */
 	if (!inode) {
 		retval = ext2fs_read_inode(fs, ino, &inode_buf);
@@ -332,7 +329,7 @@  extern errcode_t ext2fs_punch(ext2_filsys fs, ext2_ino_t ino,
 
 		if (start > ~0U)
 			return 0;
-		count = ((end - start) < ~0U) ? (end - start) : ~0U;
+		count = ((end - start + 1) < ~0U) ? (end - start + 1) : ~0U;
 		retval = ext2fs_punch_ind(fs, inode, block_buf, 
 					  (blk_t) start, count);
 	}