Messages in this thread | | | From | "Stephen C. Tweedie" <> | Date | Mon, 21 Jun 1999 14:09:59 +0100 (BST) | Subject | Re: [patch] `cp /dev/zero /tmp' (patch against 2.2.9) |
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Hi,
On Mon, 21 Jun 1999 13:33:21 +0200 (CEST), Andrea Arcangeli <andrea@suse.de> said:
> I agree that currently fdatasync is just an alias for fsync. But the > manpage seems a bit different:
> The manpage says "the metadata such as" so I thought we could skip all the > metadata (the inode timestamp looked as an example to me). I thought it > would be the application that should know if the last operations changed > the metadata or not.
No. Check the Single Unix glossary:
synchronised I/O data integrity completion
For read, when the operation has been completed or diagnosed if unsuccessful. The read is complete only when an image of the data has been successfully transferred to the requesting process. If there were any pending write requests affecting the data to be read at the time that the synchronised read operation was requested, these write requests shall be successfully transferred prior to reading the data.
For write, when the operation has been completed or diagnosed if unsuccessful. The write is complete only when the data specified in the write request is successfully transferred and all file system information required to retrieve the data is successfully transferred.
File attributes that are not necessary for data retrieval (access time, modification time, status change time) need not be successfully transferred prior to returning to the calling process.
synchronised I/O file integrity completion
Identical to a synchronised I/O data integrity completion with the addition that all file attributes relative to the I/O operation (including access time, modification time, status change time) will be successfully transferred prior to returning to the calling process.
O_DSYNC and fdatasync() can skip some of the inode updates, but when extending the file or allocating data we need to sync the inode and the indirect blocks too.
--Stephen
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