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Date: Wed, 21 Mar 2012 22:13:05 -0400 From: Ted Ts'o <tytso@....edu> To: Lukas Czerner <lczerner@...hat.com> Cc: linux-ext4@...r.kernel.org, achender@...ux.vnet.ibm.com Subject: Re: [PATCH 2/5] ext4: Correctly handle EOFBLOCKS flag in ext4_ext_punch_hole On Wed, Mar 21, 2012 at 08:23:55AM +0100, Lukas Czerner wrote: > + /* > + * This is fugly, but even though we're going to get rid of the > + * EOFBLOCKS_LF in the future, we have to handle it correctly now > + * because there are still versions of e2fsck out there which > + * would scream otherwise. Once the new e2fsck code ignoring > + * this flag is common enough this can be removed entirely. > + */ > + if (ext4_test_inode_flag(inode, EXT4_INODE_EOFBLOCKS)) { > + struct ext4_ext_path *path; > + ext4_lblk_t last_block; > + > + mutex_lock(&inode->i_mutex); > + down_read(&EXT4_I(inode)->i_data_sem); I was looking at this patch, and I was wondering why we weren't taking i_mutex earlier in ext4_ext_punch_hole(). The primary use of i_mutex is to protect writes racing with each other and with truncate. Given that punch essentially works like truncate, and all of ext4_truncate() is run with i_mutex down, and currently ext4_ext_punch_hole() (before applying this patch) doesn't isn't taking i_mutex at all, I'm wondering if we can run into problems where punch is racing against a write --- if the pages are already in mapped, then the write might not even need to take i_data_sem. Lukas, Allison --- am I missing something here? - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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