Messages in this thread | | | Date | Tue, 07 Oct 2014 20:24:02 +0200 | From | Heinrich Schuchardt <> | Subject | Re: [PATCH 1/1] fallocate: create FAN_MODIFY and IN_MODIFY events |
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Hello Andrew,
the patch in https://lkml.org/lkml/2014/10/3/56 and cited below was reviewed by Jan Kara.
Please, add it to the MM tree.
Best regards
Heinrich Schuchardt
On 07.10.2014 20:05, Jan Kara wrote: > On Mon 06-10-14 21:10:25, Heinrich Schuchardt wrote: >> On 06.10.2014 16:12, Jan Kara wrote: >>> On Fri 03-10-14 10:19:30, Heinrich Schuchardt wrote: >>>> The fanotify and the inotify API can used to monitor changes of the file >>>> system. >>>> >>>> System call fallocate modifies files. Hence it should trigger the corresponding >>>> fanotify (FAN_MODIFY) and inotify (IN_MODIFY) events. >>>> >>>> This patch adds the missing call to fsnotify_modify. >>> Well, there are different fallocate() commands and e.g. pure >>> FALLOC_FL_KEEP_SIZE call will not change any data in the file. I'm not sure >>> how much we care but I wanted to point that out... >> >> The most interesting case is FALLOC_FL_COLLAPSE_RANGE because this >> value allows to create arbitrary file content from random data. >> Hence I think we really need to create FAN_MODIFY in this case. >> >> As the fallocate(2) man page teaches: >> After a successful call, subsequent writes into the range specified >> by offset and len are guaranteed not to fail because of lack of disk >> space. >> >> So calling fallocate(fd, FALLOC_FL_KEEP_SIZE, offset, len) may >> result in different outcomes of a subsequent write depending on the >> values of offset and len. >> >> Calling fallocate for a region already zeroed will not result in any >> data change. >> >> I would like to compare fallocate() with write(). >> >> When we call write() we always create a FAN_MODIFY event even in the >> case of overwriting with identical data. >> >> So event FAN_MODIFY does not provide any guarantee that data was >> actually changed. >> >> In analogy to write() I suggest to keep the logic for fallocate() as >> trivial as possible: >> If fallocate() succeeds, create IN_MODIFY and FAN_MODIFY events. > OK, makes sense. You can add: > Reviewed-by: Jan Kara <jack@suse.cz> > > Honza >>>> Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de> >>>> --- >>>> fs/open.c | 5 +++++ >>>> 1 file changed, 5 insertions(+) >>>> >>>> diff --git a/fs/open.c b/fs/open.c >>>> index d6fd3ac..03aa8e5 100644 >>>> --- a/fs/open.c >>>> +++ b/fs/open.c >>>> @@ -295,6 +295,11 @@ int do_fallocate(struct file *file, int mode, loff_t offset, loff_t len) >>>> >>>> sb_start_write(inode->i_sb); >>>> ret = file->f_op->fallocate(file, mode, offset, len); >>>> + >>>> + /* Create inotify and fanotify events. */ >>>> + if (ret == 0) >>>> + fsnotify_modify(file); >>>> + >>>> sb_end_write(inode->i_sb); >>>> return ret; >>>> } >>>> -- >>>> 2.1.0 >>>> >>
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