From: Ritesh Harjani <riteshh@linux.ibm.com>
To: "Darrick J. Wong" <darrick.wong@oracle.com>,
Matthew Wilcox <willy@infradead.org>
Cc: jack@suse.cz, tytso@mit.edu, linux-ext4@vger.kernel.org,
adilger.kernel@dilger.ca, linux-fsdevel@vger.kernel.org,
hch@infradead.org, cmaiolino@redhat.com
Subject: Re: [PATCHv3 6/6] Documentation: Correct the description of FIEMAP_EXTENT_LAST
Date: Thu, 27 Feb 2020 10:47:52 +0530 [thread overview]
Message-ID: <20200227051753.CD17B42052@d06av24.portsmouth.uk.ibm.com> (raw)
In-Reply-To: <20200226161742.GB8036@magnolia>
On 2/26/20 9:47 PM, Darrick J. Wong wrote:
> On Wed, Feb 26, 2020 at 05:05:03AM -0800, Matthew Wilcox wrote:
>> On Wed, Feb 26, 2020 at 03:27:08PM +0530, Ritesh Harjani wrote:
>>> Currently FIEMAP_EXTENT_LAST is not working consistently across
>>> different filesystem's fiemap implementations and thus this feature
>>> may be broken. So fix the documentation about this flag to meet the
>>> right expectations.
>>
>> Are you saying filesystems have both false positives and false negatives?
>> I can understand how a filesystem might fail to set FIEMAP_EXTENT_LAST,
>> but not how a filesystem might set it when there's actually another
>> extent beyond this one.
>>
>>> * FIEMAP_EXTENT_LAST
>>> -This is the last extent in the file. A mapping attempt past this
>>> -extent will return nothing.
>>> +This is generally the last extent in the file. A mapping attempt past this
>>> +extent may return nothing. But the user must still confirm by trying to map
>>> +past this extent, since different filesystems implement this differently.
>
> "This flag means nothing and can be set arbitrarily by the fs for the lulz."
>
:) Got it. Will add more information to it.
> Yuck. I was really hoping for "This is set on the last extent record in
> the dataset generated by the query parameters", particularly becaue
> that's how e2fsprogs utilties interpret that flag.
-extent may return nothing. But the user must still confirm by trying to map
-past this extent, since different filesystems implement this differently.
+extent may return nothing. In some implementations this flag is also set on
+the last dataset queried by the user (via fiemap->fm_length).
Let me know if above looks good.
-ritesh
prev parent reply other threads:[~2020-02-27 5:18 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <cover.1582702693.git.riteshh@linux.ibm.com>
2020-02-26 9:57 ` [PATCHv3 1/6] ext4: Add IOMAP_F_MERGED for non-extent based mapping Ritesh Harjani
2020-02-26 12:26 ` Jan Kara
2020-02-26 12:33 ` Ritesh Harjani
2020-02-26 9:57 ` [PATCHv3 2/6] ext4: Optimize ext4_ext_precache for 0 depth Ritesh Harjani
2020-02-26 12:28 ` Jan Kara
2020-02-26 9:57 ` [PATCHv3 3/6] ext4: Move ext4 bmap to use iomap infrastructure Ritesh Harjani
2020-02-26 12:29 ` Jan Kara
2020-02-26 9:57 ` [PATCHv3 4/6] ext4: Make ext4_ind_map_blocks work with fiemap Ritesh Harjani
2020-02-26 12:39 ` Jan Kara
2020-02-26 12:47 ` Ritesh Harjani
2020-02-26 16:11 ` Darrick J. Wong
2020-02-27 5:27 ` Ritesh Harjani
2020-02-26 9:57 ` [PATCHv3 5/6] ext4: Move ext4_fiemap to use iomap framework Ritesh Harjani
2020-02-26 13:27 ` Jan Kara
2020-02-27 5:38 ` Ritesh Harjani
2020-02-26 9:57 ` [PATCHv3 6/6] Documentation: Correct the description of FIEMAP_EXTENT_LAST Ritesh Harjani
2020-02-26 13:05 ` Matthew Wilcox
2020-02-26 16:17 ` Darrick J. Wong
2020-02-26 17:26 ` Jan Kara
2020-02-27 3:24 ` Dave Chinner
2020-02-27 5:17 ` Ritesh Harjani [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200227051753.CD17B42052@d06av24.portsmouth.uk.ibm.com \
--to=riteshh@linux.ibm.com \
--cc=adilger.kernel@dilger.ca \
--cc=cmaiolino@redhat.com \
--cc=darrick.wong@oracle.com \
--cc=hch@infradead.org \
--cc=jack@suse.cz \
--cc=linux-ext4@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=tytso@mit.edu \
--cc=willy@infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).