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Message-ID: <20100304162039.GA5722@localhost.localdomain>
Date: Thu, 4 Mar 2010 11:20:40 -0500
From: Josef Bacik <josef@...hat.com>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Josef Bacik <josef@...hat.com>, akpm@...ux-foundation.org,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cleanup __generic_block_fiemap and fix a few minor
issues
On Thu, Mar 04, 2010 at 08:03:55AM -0800, Linus Torvalds wrote:
>
>
> On Wed, 3 Mar 2010, Josef Bacik wrote:
> >
> > 1) Some filesystems (gfs2) do not like being given non-block-aligned b_size's to
> > map, so make sure we block align the b_size.
>
> As far as I can tell, that alignment is wrong.
>
> You can't just align "len". If "start" wasn't aligned, then just aligning
> "len" is wrong. And if start is guaranteed to be aligned, how?
>
Hmm I said that wrong. GFS2 can't handle < blocksize map requests, so making
the length blocksize aligned fixed that problem, I just described it wrong.
> Also, the alignment itself is ugly as hell, doing
>
> > + len = (len + (1 << inode->i_blkbits) - 1) &
> > + ~((1 << inode->i_blkbits) - 1);
> > + map_end = start + len;
>
> When what you probably should have done is to do
>
> map_end = start + len;
>
> _before_ rounding 'start', and then after that you can now map 'start' and
> 'map_end' just using the regular "logical_to_blk" that you already use (up
> or down depending on whether the thing should be inclusive or exclusive of
> partial blocks). No?
>
> IOW, the whole thing should probably look something like
>
> sector_t start_blk, last_blk;
>
> start_blk = logical_to_blk(inode, start);
> last_blk = logical_to_blk(inode, start + len - 1);
>
> and you're done. Short, sweet, and to the point (note that "last_blk"
> really is the _last_ block, so if you want the length in blocks, it would
> be "last_blk - start_blk + 1").
>
Ahh yes thats much nicer, thank you. Here is my updated patch with your
suggestions. Thanks,
Signed-off-by: Josef Bacik <josef@...hat.com>
---
fs/ioctl.c | 81 +++++++++++++++++++++++++++++----------------------
include/linux/fs.h | 5 ++-
2 files changed, 49 insertions(+), 37 deletions(-)
diff --git a/fs/ioctl.c b/fs/ioctl.c
index 6c75110..64fed0b 100644
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -228,13 +228,22 @@ static int ioctl_fiemap(struct file *filp, unsigned long arg)
#ifdef CONFIG_BLOCK
-#define blk_to_logical(inode, blk) (blk << (inode)->i_blkbits)
-#define logical_to_blk(inode, offset) (offset >> (inode)->i_blkbits);
+static inline sector_t logical_to_blk(struct inode *inode, loff_t offset)
+{
+ return (offset >> inode->i_blkbits);
+}
+
+static inline loff_t blk_to_logical(struct inode *inode, sector_t blk)
+{
+ return (blk << inode->i_blkbits);
+}
/**
* __generic_block_fiemap - FIEMAP for block based inodes (no locking)
* @inode - the inode to map
- * @arg - the pointer to userspace where we copy everything to
+ * @fieinfo - the fiemap info struct that will be passed back to userspace
+ * @start - where to start mapping in the inode
+ * @len - how much space to map
* @get_block - the fs's get_block function
*
* This does FIEMAP for block based inodes. Basically it will just loop
@@ -250,46 +259,46 @@ static int ioctl_fiemap(struct file *filp, unsigned long arg)
*/
int __generic_block_fiemap(struct inode *inode,
- struct fiemap_extent_info *fieinfo, u64 start,
- u64 len, get_block_t *get_block)
+ struct fiemap_extent_info *fieinfo, loff_t start,
+ loff_t len, get_block_t *get_block)
{
- struct buffer_head tmp;
- unsigned long long start_blk;
- long long length = 0, map_len = 0;
+ struct buffer_head map_bh;
+ sector_t start_blk, last_blk;
u64 logical = 0, phys = 0, size = 0;
u32 flags = FIEMAP_EXTENT_MERGED;
- int ret = 0, past_eof = 0, whole_file = 0;
+ bool past_eof = false, whole_file = false;
+ int ret = 0;
- if ((ret = fiemap_check_flags(fieinfo, FIEMAP_FLAG_SYNC)))
+ ret = fiemap_check_flags(fieinfo, FIEMAP_FLAG_SYNC);
+ if (ret)
return ret;
- start_blk = logical_to_blk(inode, start);
-
- length = (long long)min_t(u64, len, i_size_read(inode));
- if (length < len)
- whole_file = 1;
+ if (len >= i_size_read(inode)) {
+ whole_file = true;
+ len = i_size_read(inode);
+ }
- map_len = length;
+ start_blk = logical_to_blk(inode, start);
+ last_blk = logical_to_blk(inode, start + len - 1);
do {
/*
* we set b_size to the total size we want so it will map as
* many contiguous blocks as possible at once
*/
- memset(&tmp, 0, sizeof(struct buffer_head));
- tmp.b_size = map_len;
+ memset(&map_bh, 0, sizeof(struct buffer_head));
+ map_bh.b_size = len;
- ret = get_block(inode, start_blk, &tmp, 0);
+ ret = get_block(inode, start_blk, &map_bh, 0);
if (ret)
break;
/* HOLE */
- if (!buffer_mapped(&tmp)) {
- length -= blk_to_logical(inode, 1);
+ if (!buffer_mapped(&map_bh)) {
start_blk++;
/*
- * we want to handle the case where there is an
+ * We want to handle the case where there is an
* allocated block at the front of the file, and then
* nothing but holes up to the end of the file properly,
* to make sure that extent at the front gets properly
@@ -297,11 +306,11 @@ int __generic_block_fiemap(struct inode *inode,
*/
if (!past_eof &&
blk_to_logical(inode, start_blk) >=
- blk_to_logical(inode, 0)+i_size_read(inode))
+ blk_to_logical(inode, 0) + i_size_read(inode))
past_eof = 1;
/*
- * first hole after going past the EOF, this is our
+ * First hole after going past the EOF, this is our
* last extent
*/
if (past_eof && size) {
@@ -309,15 +318,18 @@ int __generic_block_fiemap(struct inode *inode,
ret = fiemap_fill_next_extent(fieinfo, logical,
phys, size,
flags);
- break;
+ } else if (size) {
+ ret = fiemap_fill_next_extent(fieinfo, logical,
+ phys, size, flags);
+ size = 0;
}
/* if we have holes up to/past EOF then we're done */
- if (length <= 0 || past_eof)
+ if (start_blk > last_blk || past_eof || ret)
break;
} else {
/*
- * we have gone over the length of what we wanted to
+ * We have gone over the length of what we wanted to
* map, and it wasn't the entire file, so add the extent
* we got last time and exit.
*
@@ -331,7 +343,7 @@ int __generic_block_fiemap(struct inode *inode,
* are good to go, just add the extent to the fieinfo
* and break
*/
- if (length <= 0 && !whole_file) {
+ if (start_blk > last_blk && !whole_file) {
ret = fiemap_fill_next_extent(fieinfo, logical,
phys, size,
flags);
@@ -351,11 +363,10 @@ int __generic_block_fiemap(struct inode *inode,
}
logical = blk_to_logical(inode, start_blk);
- phys = blk_to_logical(inode, tmp.b_blocknr);
- size = tmp.b_size;
+ phys = blk_to_logical(inode, map_bh.b_blocknr);
+ size = map_bh.b_size;
flags = FIEMAP_EXTENT_MERGED;
- length -= tmp.b_size;
start_blk += logical_to_blk(inode, size);
/*
@@ -364,14 +375,14 @@ int __generic_block_fiemap(struct inode *inode,
* is marked with FIEMAP_EXTENT_LAST
*/
if (!past_eof &&
- logical+size >=
- blk_to_logical(inode, 0)+i_size_read(inode))
- past_eof = 1;
+ logical + size >=
+ blk_to_logical(inode, 0) + i_size_read(inode))
+ past_eof = true;
}
cond_resched();
} while (1);
- /* if ret is 1 then we just hit the end of the extent array */
+ /* If ret is 1 then we just hit the end of the extent array */
if (ret == 1)
ret = 0;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index ebb1cd5..7e6e47f 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2313,8 +2313,9 @@ extern int vfs_fstatat(int , char __user *, struct kstat *, int);
extern int do_vfs_ioctl(struct file *filp, unsigned int fd, unsigned int cmd,
unsigned long arg);
extern int __generic_block_fiemap(struct inode *inode,
- struct fiemap_extent_info *fieinfo, u64 start,
- u64 len, get_block_t *get_block);
+ struct fiemap_extent_info *fieinfo,
+ loff_t start, loff_t len,
+ get_block_t *get_block);
extern int generic_block_fiemap(struct inode *inode,
struct fiemap_extent_info *fieinfo, u64 start,
u64 len, get_block_t *get_block);
--
1.6.5.rc2
--
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