On 8/23/17 10:11 AM, Nikolay Borisov wrote:
> Move the blocksize and max_extent variables to the top of the file since they
> are globals. Also blocksize never changes to mark it const. Also stop passing
> max_extents around and refer to it directly.
Having looked at this for way too long, here are things that I think could be
done, in more or less this order as separate patches, but rearrange or
add/remove as you see fit...
- Get rid of the blocksize variable, and use BTOBBT()
- Turn num_extents into #define EXTENT_BATCH 32, fixed query map size
- make max_extents global if you like
- Clean up the control loop(s) and exit point(s), there are now exits on:
+ fm_mapped_extents == 0 (we got none from our query)
+ FIEMAP_EXTENT_LAST set (kernel tells us this one is last)
+ max_extents hit (we hit the user's limit)
+ end of requested range hit (after range is implemented)
... there's a lot in there that is messy. :/
- Fix the "-n" behavior (a minimally as possible) and update xfs_bmap(8) to match
finally:
- Implement your range query (I think this can be done by simply
modifying the initial fm_start and fm_length, no? Or, by only
modifying fm_start, and breaking out of the loop when we retrieve
an extent that goes beyond the end of the requested region?)
Other things I noticed:
- print_plain and print_verbose are pretty nasty the way they
hide increments of cur_extent & last_logical. I think it would
be better to:
+ pass cur_extent & last_logical by value
+ return nr of extents printed, so the caller can increment cur_extent
+ update last_logical in fiemap_f after, not in, the print functions
- The last hunk that handles a hole at EOF is ick; something like this
may be better, re-using the print functions with a special "EOF
extent"; the print functions would then return after printing a hole
if they are handed a 0 length extent with LAST set, or something.
/* Handle a hole at EOF if there is one */
if (cur_extent && last_logical < st.st_size) {
struct fiemap_extent hole = { 0 };
/* special 0-length extent to show formatters it's hole @ EOF */
hole.fe_logical = st.st_size;
hole.fe_length = 0;
hole.fe_flags = FIEMAP_EXTENT_LAST;
if (vflag)
print_verbose(&hole, foff_w, boff_w, tot_w, flg_w,
max_extents, cur_extent, last_logical);
else
print_plain(&hole, lflag,
max_extents, cur_extent, last_logical);
}
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