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[PATCH V2] xfs_io: fix fiemap loop continuation

To: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Subject: [PATCH V2] xfs_io: fix fiemap loop continuation
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Tue, 14 Feb 2012 11:45:32 +1100
Cc: xfs@xxxxxxxxxxx
In-reply-to: <20120213190903.GA12477@xxxxxxxxxxxxx>
References: <1328163674-9420-1-git-send-email-david@xxxxxxxxxxxxx> <20120213190903.GA12477@xxxxxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Mon, Feb 13, 2012 at 02:09:03PM -0500, Christoph Hellwig wrote:
> This actually seems to break 252 and 255 for me.

Ok, there was some code that expected last_logical to be in FSB
units, not bytes that I failed to convert.

Fixed version below.

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx


xfs_io: fix fiemap loop continuation

From: Dave Chinner <dchinner@xxxxxxxxxx>

When the fiemap command needs to retrieve more extents from the
kernel via a subsequent IO, it calculates the next logical block to
retrieve in file system block units. the fiemap needs the start
offset in bytes, not filesystem blocks.  Hence if the fiemap command
can loop forever retrieving the same blocks if the logical offset
offset of the next block in filesystem block units is smaller than
the number of bytes in a filessytem block. i.e. it will just loop
retreiving the first 32 extents from offset block zero.

Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>

---
Version 2
o Fix remaining cases where last_logical was expected to be in FSB
  units rather than bytes.

 io/fiemap.c |   33 ++++++++++++++++++---------------
 1 files changed, 18 insertions(+), 15 deletions(-)

diff --git a/io/fiemap.c b/io/fiemap.c
index 066e693..e32a416 100644
--- a/io/fiemap.c
+++ b/io/fiemap.c
@@ -75,12 +75,14 @@ print_verbose(
        __u64                   *last_logical)
 {
        __u64                   lstart;
+       __u64                   llast;
        __u64                   len;
        __u64                   block;
        char                    lbuf[48];
        char                    bbuf[48];
        char                    flgbuf[16];
 
+       llast = *last_logical / blocksize;
        lstart = extent->fe_logical / blocksize;
        len = extent->fe_length / blocksize;
        block = extent->fe_physical / blocksize;
@@ -88,11 +90,11 @@ print_verbose(
        memset(lbuf, 0, sizeof(lbuf));
        memset(bbuf, 0, sizeof(bbuf));
 
-       if (lstart != *last_logical) {
-               snprintf(lbuf, sizeof(lbuf), "[%llu..%llu]:", *last_logical,
+       if (lstart != llast) {
+               snprintf(lbuf, sizeof(lbuf), "[%llu..%llu]:", llast,
                         lstart - 1ULL);
                printf("%4d: %-*s %-*s %*llu\n", *cur_extent, foff_w, lbuf,
-                      boff_w, _("hole"), tot_w, lstart - *last_logical);
+                      boff_w, _("hole"), tot_w, lstart - llast);
                (*cur_extent)++;
                memset(lbuf, 0, sizeof(lbuf));
        }
@@ -108,7 +110,7 @@ print_verbose(
               boff_w, bbuf, tot_w, len, flg_w, flgbuf);
 
        (*cur_extent)++;
-       *last_logical = lstart + len;
+       *last_logical = extent->fe_logical + extent->fe_length;
 }
 
 static void
@@ -121,19 +123,20 @@ print_plain(
        __u64                   *last_logical)
 {
        __u64                   lstart;
+       __u64                   llast;
        __u64                   block;
        __u64                   len;
 
+       llast = *last_logical / blocksize;
        lstart = extent->fe_logical / blocksize;
        len = extent->fe_length / blocksize;
        block = extent->fe_physical / blocksize;
 
-       if (lstart != *last_logical) {
+       if (lstart != llast) {
                printf("\t%d: [%llu..%llu]: hole", *cur_extent,
-                      *last_logical, lstart - 1ULL);
+                      llast, lstart - 1ULL);
                if (lflag)
-                       printf(_(" %llu blocks\n"),
-                              lstart - *last_logical);
+                       printf(_(" %llu blocks\n"), lstart - llast);
                else
                        printf("\n");
                (*cur_extent)++;
@@ -151,7 +154,7 @@ print_plain(
        else
                printf("\n");
        (*cur_extent)++;
-       *last_logical = lstart + len;
+       *last_logical = extent->fe_logical + extent->fe_length;
 }
 
 int
@@ -252,7 +255,7 @@ fiemap_f(
                memset(fiemap, 0, map_size);
                fiemap->fm_flags = fiemap_flags;
                fiemap->fm_start = last_logical;
-               fiemap->fm_length = -1;
+               fiemap->fm_length = -1LL;
                fiemap->fm_extent_count = num_extents;
 
                ret = ioctl(file->fd, FS_IOC_FIEMAP, (unsigned long)fiemap);
@@ -281,6 +284,7 @@ fiemap_f(
                                print_plain(extent, lflag, blocksize,
                                            max_extents, &cur_extent,
                                            &last_logical);
+
                        if (extent->fe_flags & FIEMAP_EXTENT_LAST) {
                                last = 1;
                                break;
@@ -303,22 +307,21 @@ fiemap_f(
                return 0;
        }
 
-       if (cur_extent && last_logical < (st.st_size / blocksize)) {
+       if (cur_extent && last_logical < st.st_size) {
                char    lbuf[32];
 
                snprintf(lbuf, sizeof(lbuf), "[%llu..%llu]:",
-                        last_logical, (st.st_size / blocksize) - 1);
+                        last_logical / blocksize, (st.st_size / blocksize) - 
1);
                if (vflag) {
                        printf("%4d: %-*s %-*s %*llu\n", cur_extent,
                               foff_w, lbuf, boff_w, _("hole"), tot_w,
-                              (st.st_size / blocksize) - last_logical);
+                              (st.st_size - last_logical) / blocksize);
                } else {
                        printf("\t%d: %s %s", cur_extent, lbuf,
                               _("hole"));
                        if (lflag)
                                printf(_(" %llu blocks\n"),
-                                      (st.st_size / blocksize) -
-                                      last_logical);
+                                      (st.st_size - last_logical) / blocksize);
                        else
                                printf("\n");
                }

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