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On 2022-11-08, Laurence Perkins <lperkins@×××××××.net> wrote: |
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>>> |
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>>>> What happens when the bad block is _already_allocated_ to a file? |
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>> |
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>>> [...] |
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>> |
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>>Thanks. I guess I should have been more specific in my question. |
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>> |
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>>What does e2fsck -c do to the filesystem structure when it discovers |
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>>a bad block that is already allocated to an existing inode? |
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>> |
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>>Is the inode's chain of block groups left as is -- still containing |
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>>the bad block that (according to the man page) "has been added to |
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>>the bad block inode"? Presumably not, since a block can't be |
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>>allocated to two different inodes. |
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>> |
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>>Is the "broken" file split into two chunks (before/after the bad |
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>>block) and moved to the lost-and-found? |
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>> |
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>>Is the man page's description only correct when the bad block is |
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>>currently unallocated? |
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> |
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> If I recall correctly, it will add any unreadable blocks to its |
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> internal list of bad sectors, which it will then refuse to allocate |
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> in the future. |
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I'm asking what happens to the file containing the bad block. Perphaps |
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nothing. The man page says the block is added to the "bad block |
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inode". If that block was already allocated, is the bad block is now |
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allocated to two different inodes? |
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|
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> I don't believe it will attempt to move the file to elsewhere until |
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> it is written since: |
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> |
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> A) what would you then put in that block? You don't know the contents. |
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You wouldn't put anything in that block. |
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One solution that comes to mind would be to truncate the file |
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immediately before the bad block (we'll call that truncated file the |
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"head"). Then you allocate a new inode to which you assign all of the |
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blocks after the bad block (we'll call that the "tail"). The bad block |
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is then moved to the "bad blocks inode" and the head/tail files are |
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moved into the lost+found. |
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> B) Moving the file around would make attempts to recover the data |
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> from that bad sector significantly more difficult. |
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Yes, probably. Any manipulation of a filesystem (like adding the block |
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to the bad block inode) on a failing disk seems like a bad idea. |
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|
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-- |
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Grant |
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