On 09/28/2011 03:21 PM, Yongqiang Yang wrote: > On Wed, Sep 28, 2011 at 2:32 PM, Jeff Liu <jeff.liu@xxxxxxxxxx> wrote: >> Hello all, >> >> This is the V2 for add SEEK_DATA/SEEK_HOLE support to ext4. >> In V1, I copied all the codes regarding fetching delayed-extents out to >> my seek callback function, it's stupid to duplicate the code blocks. >> >> Now the idea is, since the delayed-extents is the main concern to search >> extents for both fiemap and seek, so IMHO, it's better to consolidate >> this procedure into a new function(get_delayed_extent() in my patch), >> and call it in fiemap and seek call-back functions if necessary. In >> this way, when yongqiang's delayed-extents tree is ready, we only need >> to modify the code block at get_delayed_extent() accordingly. >> >> In addition, yongqiang has pointed out there might be a deadlock, but >> per my understood, as the target inode already locked via i_mutex in >> ext4_llseek() before, this lock can prevent any modification to the >> file, and we call find_get_pages_tag() when trying to fetch the dirty >> pages, this function using rcu read lock, it also safe to read. So I >> have no idea what's wrong, could anyone please kindly point me out in >> this case? I'm definitely a newbie to this list, sorry for my ignorant. > Ok. There is no deadlock, fiemap releases i_data_sem before calling > get_delayed_extent(). > > BTW: It seems that there is a bug in fiemap according to code, I am > not sure which commit introduced it, delayed extents beyond last > allocated block are ignored. Hmm... could you show me a bit more detailed info with the test scenario if convenient? I can help testing, at least 3.1.0-rc2+ is works to me. Also, upstream coreutils-cp(1) has been well tested for ext4, it could be used for fiemap tests based on the extent_scan module: http://git.savannah.gnu.org/cgit/coreutils.git/tree/src/extent-scan.c?h=next&id=b56b53bd70b1f8fa2b5a95d4569bb72a2419b5cd Thanks, -Jeff > > Yongqiang. >> >> Anyway, I'd like to post the revised for your guys review first. >> In have split the modification to two patches this time, since I hope to >> make it looks more convenient for the review purpose. >> >> The 1st patch, remove the delayed-extents fetching procedure to a >> function named as get_delayed_extent(), and modify the >> ext4_ext_fiemap_cb() accordingly. >> >> The 2nd path add the ext4_ext_seek_cb() to implement the >> SEEK_HOLE/SEEK_DATA stuff based on previous code change. >> >> Testing: >> ======== >> In addition to the test cases mentioned in V1, I also done another tests >> through sunil's seek test program, please refer to: >> http://oss.oracle.com/~smushran/seek_data/seek_test.c >> >> To ensure the 1st patch does not cause regression issue on fiemap, I >> have done some tests via cp(1) with fiemap copy support, the sparse file >> used for this test is produced by: >> python -c "f=open('./sptest', 'w'); [(f.seek(x) or f.write(str(x))) for >> x in range(1, 1000000000, 99999)]; f.close() >> >> >> Any feedback are appreciated! >> >> >> Thanks, >> -Jeff >> > > > -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
