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SEEK_DATA has interesting behaviour for sparse files on ZFS. A sparse file

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with 128K of random data and truncated to 800K can have SEEK_DATA return -1
when given an offset of 128K. On UFS, the SEEK_DATA returns 800K (the size
of the file). SEEK_HOLE on ZFS seems to behave the same as UFS.

To handle this, map -1 to the size of the file (`end') when lseek returns
this for either SEEK_HOLE or SEEK_DATA. When sparse files are not supported
by the file system both `hole' and `data' will now be equal to `end' and we
will treat the entire file as data. This way, the -1 return for SEEK_DATA
on ZFS will end up doing the right thing.

Reported by: gjb@

MFC after:	3 days
This commit is contained in:
Marcel Moolenaar 2014-11-12 00:10:27 +00:00
parent bea71143ed
commit 9ba57342c9
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=274410
1 changed files with 5 additions and 3 deletions
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8
usr.bin/mkimg/image.c
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@ -405,16 +405,18 @@ image_copyin_mapped(lba_t blk, int fd, uint64_t *sizep)
error = 0;
while (!error && cur < end) {
hole = lseek(fd, cur, SEEK_HOLE);
if (hole == -1)
hole = end;
data = lseek(fd, cur, SEEK_DATA);
if (data == -1)
data = end;
/*
* Treat the entire file as data if sparse files
* are not supported by the underlying file system.
*/
if (hole == -1 && data == -1) {
if (hole == end && data == end)
data = cur;
hole = end;
}
if (cur == hole && data > hole) {
hole = pos;