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Andrew Morton wrote: > Yes, there can be issues with needing to allocate journal space within the > context of a commit. But no-no, this isn't required. we only need to mark pages/blocks within transaction, otherwise race is possible when we allocate blocks in transaction, then transacton starts to commit, then we mark pages/blocks to be flushed before commit. > a) If the page has newly allocated space on disk then the metadata which > refers to that page is already in the journal: no new journal space > needed. > > b) If the page doesn't have space allocated on disk then we don't need > to write it out at ordered-mode commit time, because the post-recovery > filesystem will not have any references to that page. > > c) If the page is dirty due to overwrite then no metadata update was required. > > IOW, under what circumstances would an ordered-mode commit need to allocate > space for a delayed-allocate page? no need to allocate space within commit thread, I think. only to take care of the race I described above. in hackish version of data=ordered for delayed allocation I used counter of submitted bio's with newly-allocated blocks and commit thread waits for the counter to reach 0. > > However b) might lead to the hey-my-file-is-full-of-zeroes problem. > thanks, Alex - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | ||||||||||||
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