On Thu, Jun 27, 2013 at 06:28:21PM +0530, Nagachandra P wrote: > Hi Theodore, > > Could you point me to the code where ext4_std_err is not triggered > because of LMK? As I see it, if a memory allocation returns error in > some of the case ext4_std_error would invariably be called. Please > consider the following call stack Yes, that's one example where a memory allocation failure can lead to ext4_std_error() getting called, and I've already acknowledged that's one that we need to fix (although as I said, fixing it may be tricky, short of calling congestion_wait() and then retrying the allocation, and hoping that in the meantime the OOM killer has freed up some memory). If you'd could give me a list of other memory allocations where ext4_std_error() could get called, please let me know. Note that in the jbd2 layer, though, we handle a memory allocation failure by retrying the allocation, to avoid this the file system getting marked read/only. Examples of this include in jbd2_journal_write_metadata_buffer(), and in jbd2_journal_add_journal_head() when it calls journal_alloc_journal_head(). (Although the way we're doing the retry in the latter case is a bit ugly and we're not sleeping with a call to congestion_wait(), so it's something we should clean up.) To give you an example of the intended use of ext4_std_error(), if the journal commit code runs into a disk I/O error while writing to the journal, the jbd2 code has to mark the journal as aborted. This could happen because the disk has gone off-line, or the HDD has run out of spare disk sectors in its bad block replacement pool, so it has to return a write error to the OS. Once the journal has been marked as aborted, the next time the ext4 code tries to access the journal, by starting a new journal handle, or marking a metadata block dirty, the jbd2 function will return an error, and this will cause ext4_std_error() to be called so the file system can be marked as requiring a file system check. Regards, - Ted -- 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
